SSC San Diego TD 627 Revision D,
Annotated Bibliography of Publications from the U.S. Navy's Marine Mammal Program, May 1998


1. SOUND/SONAR/COMMUNICATION

Altes, R. A., W. E. Evans, and C. S. Johnson. 1975. Cetacean Echolocation Signals and a New Model for the Human Glottal Pulse. Jour. Acoust. Soc. Am. 57 (5): 1221-1224.

A theoretical explanation for cetacean sonar systems can also be applied to human speech. The theory leads to a mathematical model of the human glottal pulse that is considerably different from those employed in the past.

Altes, R. A., and S. H. Ridgway. 1980. Dolphin Whistles as Velocity-sensitive Sonar/Navigation Signals. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 853-854.

A certain type of dolphin whistle that has been classified as a distress whistle but which also occurs under other circumstances is very similar to signals that can be used for accurate Doppler measurement. On theoretical grounds, such whistles have characteristics that might make them useful for sonar navigation, but behavioral experiments are needed.

Au, W. W. L., R. W. Floyd, R. H. Penner, and A. E. Murchison. 1974. Measurement of Echolocation Signals in the Atlantic Bottlenosed Dolphin, Tursiops truncatus Montagu, in Open Waters. Jour. Acoust. Soc. Am. 56 (4): 1280-1290.

Echolocation signals of two bottlenosed dolphins echolocating on targets at distances of 60 to 80 yards were measured. Peak energies between 120 and 130 kHz were recorded, with sound pressure levels at least 30 dB higher than any previously reported.

Au, W. W. L., and C. E. Hammer. 1978. Analysis of Target Recognition via Echolocation by an Atlantic Bottlenosed Porpoise (Tursiops truncatus). (Abs.) Jour. Acoust. Soc. Am. 64 (Suppl. 1): S87.

From targets previously used for a study of porpoise echolocation, echoes of porpoise-like signals were obtained and analyzed. The shape of the spectrum was predominantly influenced by the first two echo components, those from the front face and the interior boundary of the rear face. Matched-filter analysis corresponds closely with the animal’s performance.

Au, W. W. L., R. W. Floyd, and J. E. Haun. 1978. Propagation of Atlantic Bottlenosed Dolphin Echolocation Signals. Jour. Acoust. Soc. Am. 64: 411-422.

The propagational characteristics of high-frequency signals (peak energies above 100 kHz) were determined by a series of measurements made in open water. The 3-dB broadband beamwidth was found to be approximately 10 inches in both the horizontal and vertical planes. The major axis of the vertical beam was directed at an angle of 20 inches above the plane defined by the animal’s teeth.

Au, W. W. L. 1980. Echolocation Signals of the Atlantic Bottlenosed Dolphin (Tursiops truncatus) in Open Waters. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 251-282.

A review, with additional previously unpublished data.

Au, W. W. L., and C. E. Hammer. 1980. Target Recognition via Echolocation by Tursiops truncatus. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 855-858.

Target recognition and discrimination behavior was studied as a function of target composition and internal structure. The targets were then acoustically examined using a simulated dolphin echolocation signal to determine the salient cues that could enable the animal to discriminate the targets.

Au, W. W. L., R. J. Schusterman, and D. A. Kersting. 1980. Sphere-Cylinder Discrimination via Echolocation by Tursiops truncatus. In: Animal Sonar Systems, R.G. Busnel and J.F. Fish (eds.). Plenum Press, New York, pp. 859-862.

Discrimination of spherical and cylindrical targets of the same material but with dimensions chosen such that they had overlapping target strengths was demonstrated. Acoustic examination of echoes from the targets indicated they were very similar, but it was found that the water-surface-reflected component of the echoes differed with the two shapes and apparently provided the essential cue.

Au, W. W. L., and K. J. Snyder. 1980. Long-Range Target Detection in Open Waters by an Echolocating Atlantic Bottlenosed Dolphin. Jour. Acoust. Soc. Am. 68 (4): 1077-1084.

The dolphin was found to be capable of detecting a 7.62-cm diameter stainless steel water-filled sphere at 113 m (50 percent target detection threshold range). Results with this sphere were congruent with those obtained previously with a sphere less than half its diameter.

Au, W. W. L., and R. H. Penner. 1981. Target Detection in Noise by Echolocating Atlantic Bottlenosed Dolphins. Jour. Acoust. Soc. Am. 70 (3): 687-693.

The capability of two dolphins to detect a 7. 62-cm water-filled stainless steel sphere was tested in the presence of white noise. The response of an ideal energy detector was found to match the behavioral results as a function of the echo signal-to-noise ratio.

Au, W.W.L, R.H. Penner, and J. Kadane. 1982. Acoustic Behavior of Echolocating Atlantic Bottlenose Dolphins. Jour. Acoust. Soc. Am. 71 (5): 1269-1275.

A click detector was used to monitor acoustic emissions of two dolphins performing a target detection task in white noise. Average number of clicks emitted per trial increased with masking noise until a particular level was reached, then decreased with further increases in noise level. Response levels and click intervals were also analyzed.

Au, W. W. L., and P. W. B. Moore. 1982. Directional Hearing in the Atlantic Bottlenosed Dolphin (Tursiops truncatus). (Abs.) Jour. Acoust. Soc. Am. 70 (Suppl. 1): S42.

Directional hearing sensitivity in the horizontal plane was measured for pure-tone frequencies of 30, 60, and 120 kHz (for vertical beam pattern results, see Moore and Au, 1981). The receiving directivity index for beam patterns in both the vertical and horizontal planes was 10, 15, and 21 dB respectively for the three frequencies.

Au, W. W. L., D. A. Carter, R. H. Penner, and B. L. Scronce. 1982. Beluga Whale Echolocation Signals in Two Different Ambient Noise Environments. Jour. Acoust. Soc. Am. 72 (Suppl. 1): S42.

In Kaneohe Bay, Hawaii, the echolocation clicks emitted by a beluga during a target identification task had higher peak frequencies and higher bandwidths than were measured earlier in the lower ambient noise environment of San Diego Bay.

Au, W. W. L., and D. W. Martin. 1983. Insights into Dolphin Sonar Discrimination Capabilities from Broadband Sonar Discrimination Experiments with Human Subjects. (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): S73.

When digital recordings made of echoes from targets ensonified with a dolphin-like signal were played back at a slower rate to subjects, humans could make fine target discriminations about as well as dolphins can under less controlled conditions.

Au, W. W. L., and P. W. B. Moore. 1984. Receiving Beam Patterns and Directivity Indices of the Atlantic Bottlenosed Dolphin (Tursiops truncatus). Jour. Acoust. Soc. Am. 75 (1): 255-262.

Receiving beam patterns were measured in both the vertical and horizontal planes for frequencies of 30, 60, and 120 kHz. Beam patterns in both planes became narrower as the frequency increased.

Au, W. W. L., and C. W. Turl. 1984. Dolphin Biosonar Detection in Clutter: Variation in the Payoff Matrix. Jour. Acoust. Soc. Am. 76 (3): 955-957.

A bottlenosed dolphin was trained to detect targets in the interference of a clutter screen (spaced cork spheres in a rectangular array). The number of pieces of fish given for correct detections and rejections was varied. Increased food reinforcement resulted in an increase in both correct detection and false alarm rates, but detection sensitivity was approximately constant.

Au, W. W. L., D. A. Carder, R. H. Penner, and B. L. Scronce. 1985. Demonstration of Adaptation in Beluga Whale Echolocation Signals. Jour. Acoust. Soc. Am. 77 (2): 726-730.

The echolocation signals of the same beluga were measured first in San Diego Bay and later in Kaneohe Bay, Hawaii, where the ambient noise level was much higher. In Kaneohe Bay, the beluga shifted its signals to higher frequencies and intensities.

Au, W. W. L., and P. W. B. Moore. 1986. The Perception of Complex Echoes by an Echolocating Bottlenosed Dolphin. Jour. Acoust. Soc. Am. 80 (Suppl. 1A): S107.

Describes a series of experiments using electronic targets to study how dolphins perceive echoes from targets. Found that dolphins performed like an energy detector with an integration time of 264 us.

Au, W. W. L., P. W. B. Moore, and D. A. Pawloski. 1986. Echolocation Transmitting Beam of the Atlantic Bottlenosed Dolphin. Jour. Acoust. Soc. Am. 80: 688-691.

The transmitting beam patterns of echolocation signals were measured in the vertical and horizontal planes with an array of seven hydrophones.

Au, W. W. L., P. W. B. Moore, and S. W. Martin. 1987. Phantom Electronic Target for Dolphin Sonar Research. Jour. Acoust. Soc. Am. 82 (2): 711-713.

A microprocessor-controlled electronic target simulator was developed and used in dolphin echolocation detection experiments. The system captures and stores signals from the dolphin and projects back virtual or "phantom" echoes from replicas of the signals. The system gives the experimenter precise control of target echo characteristics during testing.

Au, W. W. L. 1988. Instrumentation for Dolphin Echolocation Experiments. (Abs.) Jour. Acoust. Soc. Am. 83 (Suppl. 1): S15.

Describes instrumentation, developed at NOSC, used in dolphin echolocation experiments and interfaceable with personal computers.

Au, W. W. L. 1988. Sonar Target Detection and Recognition by Odontocetes. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 451-465.

Reviews sonar detection and discrimination experiments conducted in open waters of Kaneohe Bay, Hawaii with bottlenosed dolphins and beluga whales. Discusses experiments to determine capabilities for (1) maximum detection range, (2) target detection in noise, (3) target detection in reverberation, and (4) target recognition and shape discrimination.

Au, W. W. L. 1988. Detection and Recognition Models of Dolphin Sonar Systems. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 753-768.

Examines dolphin sonar systems from theoretical and empirical perspectives. Results from a variety of experiments are used to establish the dolphins’ sonar operating characteristics. Although humans and dolphins seem to have similar abilities to detect target echoes in noise and to discriminate fine target features, most manmade sonars do not use human auditory capabilities. Dolphins, however, typically use broadband transient-like pulses that are well-matched to their auditory and pattern recognition capacities.

Au, W. W. L., P. W. B. Moore, and D. A. Pawloski. 1988. Detection of Complex Echoes in Noise by an Echolocating Dolphin. Jour. Acoust. Soc. Am. 83 (2): 662-668.

"Phantom" echo techniques were used in a series of experiments to investigate how dolphins perceive complex echoes in masking noise. The dolphin performed like an energy detector with an integration time of approximately 264 us.

Au, W. W. L., R. H. Penner, and C. W. Turl. 1988. Propagation of Beluga Echolocation Signals. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 47-51.

Discusses a series of measurements made in Kaneohe Bay. The beluga’s transmitted beam is slightly narrower than the bottlenosed dolphin’s. The transition from near-to-far field occurs within 1 meter of the beluga’s snout. The beluga’s signal generator is equivalent to a planar circular aperture of about 13 cm.

Au, W. W. L., and D. W. Martin. 1988. Sonar Discrimination of Metallic Plates by Dolphins and Humans. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 809-813.

Digitized broadband echoes from a standard series of metal targets were played to human listeners and discrimination performance was compared with dolphins. Echoes at normal incidence did not seem to contain much useful information for discrimination, but useful cues developed as the incident angle increased. Matched- filter response showed enriched highlight structure at incident angles up to 150 degrees.

Au, W. W. L., and P. W. B. Moore. 1988. The Perception of Complex Echoes by an Echolocating Dolphin. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 295-299.

An echolocating bottlenosed dolphin was required to detect target echoes in noise. Results verified the "phantom echo" technique, estimated a 264 us integration time for the dolphin, and showed that the dolphin’s performance matched that expected for an energy detector.

Au, W. W. L., and J. L. Pawloski. 1988. The Perception of Time-Separation Pitch by Dolphins. (Abstract) Jour. Acoust. Soc. Am. 83 (Suppl. 1): S51.

Discusses an experiment in which the capability of a dolphin to perceive the difference between noise with a rippled frequency spectrum and noise with a flat spectrum. Noise with a rippled spectrum is generated by summing broadband noise with its delayed replica. The lower and upper limits of the time-delay used to generate noise stimuli with ripple spectra that can be perceived by a dolphin were determined. Noise with rippled spectrum generate time-separation pitch in the human auditory system. It was suggested that because dolphins can perceive the presence of ripples in the spectrum of noise they may also be able to perceive time-separation pitch.

Au, W. W. L., and J. L. Pawloski. 1989. Detection of Noise with Rippled Spectra by the Atlantic Bottlenosed Dolphin. Jour. Acoust. Soc. Am. 86 (2): 591-596.

A dolphin was required to discriminate between rippled and nonrippled underwater noise in three related experiments. The dolphin’s sensitivity was greater for the cos+ than the cos— stimuli and greater for delays of 100 us Other results relate the dolphin’s performance to the noise center frequency and suggest that dolphins may perceive time-separation pitch.

Au, W. W. L., and D. W. Martin. 1989. Insights into Dolphin Sonar Discrimination Capabilities from Human Listening Experiments. Jour. Acoust. Soc. Am. 86 (5): 1662-1670.

Sonar discrimination experiments with human subjects were compared to dolphin experiments using the same targets. Under laboratory conditions, humans made fine target discriminations about as well as dolphins tested under less controlled conditions. Human subjects generally reported time-domain cues were more useful than frequency-related process in analyzing the echoes.

Au, W. W. L., and L. L. Jones. 1989. Target Strength Measurements of Nets and Implications Concerning Incidental Take of Dall’s Porpoises. (Abs.) Eighth Biennial Conf. on the Biology of Marine Mammals, Pacific Grove, CA., p. 3.

The target strength of some nets used in drift-net and bottom set-net fishing was measured using simulated dolphin sonar signals. The biosonar detection ranges of a monofilament drift-net used in the high-sea salmon mothership fishery were calculated using the sonar equation and detection threshold obtained with Tursiops truncatus. It was concluded that echolocating dolphins should be able to detect nets at sufficient ranges to avoid entanglement. Several reasons why entanglement still occurs were suggested.

Au, W. W. L., and D. A. Pawloski. 1989. A Comparison of Signal Detection Between an Echolocating Dolphin and an Optimal Receiver. Jour. Comp. Physiol. A 164: 451-458.

Dolphin echolocation performance in noise was evaluated in two related experiments using electronic "phantom" targets. The first experiment estimated the echo energy-to-noise ratio at the dolphin’s detection threshold. The second experiment evaluated the dolphin’s receiver operating characteristics in a detection task. Results indicate the dolphin required approximately 7.4 dB higher energy-to-noise ratio than an optimal detector to detect the simulated target.

Au, W. W. L. 1990. Target Detection in Noise by Echolocating Dolphins. In: Sensory Abilities of Cetaceans, J. A. Thomas and R. A. Kastelein (eds.). Plenum Press, New York, pp. 203-216.

Reviews dolphin sonar detection experiments in artificial and natural noise conditions. The integration time of the dolphin detection system is discussed. The dolphin detection performance is compared with an energy detector as well as an ideal or optimal receiver.

Au, W. W. L., and D. A. Pawloski. 1990. Cylinder Wall Thickness Difference Discrimination by an Echolocating Dolphin. Jour. Acoust. Soc. Am. 88 (Suppl. 1): S4.

Discusses an experiment testing the capability of an echolocating Tursiops truncatus to discriminate the differences in the wall thickness of hollow aluminum cylinders in the free field and with artificial noise added. The dolphin could discriminate a wall thickness difference of -0.23 mm and +0.27 mm for a standard wall thickness of 6.35 cm. Back-scatter measurements suggested that if the dolphin used time domain cues, it may be able to detect time differences between two echo highlights within +500 ns. If frequency domain cues were used, the dolphin may be able to detect frequency shifts as small as 3 kHz. If the dolphin used time-separation pitch cues, it may be able to detect differences of 450 Hz.

Au, W. W. L., and P. W. B. Moore. 1990. Critical Ratio and Critical Bandwidth for the Atlantic Bottlenosed Dolphin. Jour. Acoust. Soc. Am. 88 (3): 1635-1638.

Critical ratio was measured for a dolphin for frequencies between 30 and 140 kHz. The data below 100 kHz were consistent with previous critical ratio data. Critical bandwidth was also measured at frequencies of 30, 60 and 120 kHz. The critical bandwidth was larger than the critical ratios by 2.2 to 11 times.

Au, W. W. L., and C. W. Turl. 1991. Material Composition Discrimination of Cylinders at Different Aspect Angles by an Echolocating Dolphin. Jour. Acoust. Soc. Am. 89 (5): 2448-2451.

Discusses an experiment describing the ability of Tursiops truncatus to discriminate a hollow aluminum cylinder from a stainless steel cylinder of the same dimensions at different target aspect angles. The results indicated that the dolphin could discriminate the aluminum and steel cylinders at an accuracy of 100 percent when the longitudinal axis of the cylinders were oriented perpendicular to the direction of the animal. Performance dropped to a minimum of 80 percent when the longitudinal axis was at a 45-degree aspect angle. Discrimination between the hollow aluminum cylinder and a solid coral cylinder was also tested. The dolphin also discriminated the hollow aluminum and solid coral cylinders almost perfectly at all angles tested.

Au, W. W. L., and L. L. Jones. 1991. Acoustic Reflectivity of Nets: Implications Concerning Incidental Take of Dolphins. Marine Mammal Science 7 (3): 258-273.

For a summary see Au and Jones, 1989.

Au, W.W.L. 1993. The Sonar of Dolphins. Springer-Verlag, New York. 277 pp.

First book to summarize research on the physiological, mathematical, acoustical, and engineering aspects of dolphin sonar, the sophisticated and highly sensitive sensory mechanism resulting from millions of years of evolutionary refinement. It continues to be superior to man-made sonar in its ability to recognize and classify targets in noisy environments.

Au, W.W.L., J.L. Pawloski, T.W. Cranford, R.C. Gisiner, and P.E. Nachtigall. 1993. Transmission Beam Pattern of False Killer Whale. (Abs.) Jour. Acoust. Soc. Am. 93 (4, Pt. 2): 2358.

Reports on an open-ocean study measuring vertical and horizontal beam patterns of a false killer whale. Reports the major axis of the vertical beam is directed slightly downward. Suggests differences in the fatty structure of the melons of Pseudorca, Tursiops and Delphinapterus could explain differences in elevation angle of their respective vertical beam axes.

Au, W.W.L. and P.E. Nachtigall. 1993. The Effects of Noise on Dolphin Echolocation. (Abs.) Jour. Acoust. Soc. Am. 94 (3, Pt. 2): 1829.

Discusses experiments demonstrating target detection and discrimination capabilities of echolocating dolphins can be severely degraded by introduction of masking noise. Reports on changes in signal intensity and frequency by cetaceans to compensate for changes in the ambient noise environment.

Au, W.W.L., J.L. Pawloski, P.E. Nachtigall, T.W. Cranford and R.C. Gisiner. 1993. Echolocation Signals and Transmission Beam Pattern of a False Killer Whale (Pseudorca crassidens). (Abs.) Tenth Biennial Conf. on the Biology of Marine Mammals, Galveston, TX, Nov. 11-15.

See Au et al., 1993. above.

Au, W.W.L. 1994. Acoustic Backscatter from a Dolphin. (Abs.) Jour. Acoust. Soc. Am. 95 (5, Pt. 2): 2881.

Backscatter measurements were made on a stationary Atlantic bottlenosed dolphin under controlled conditions to determine target strength. Most acoustic energy was reflected from the area between the dorsal and pectoral fins, corresponding to the location of the dolphin’s lungs.

Au, W.W.L. 1994. Acoustics of Echolocating Dolphins and Small Whales. (Abs.)International School of Ethology Workshop, Ettore Majoranna Centre for Scientific Culture, Erice, Sicily, Nov. 4-9.

Discusses echolocation in three species of cetaceans, considering such topics as auditory sensitivity, spectral analysis capabilities, directional hearing, echolocation signals and propagation of those signals from the animals’ heads.

Au, W.W.L. 1994. Sonar Detection of Gillnets by Dolphins: Theoretical Predictions. Rep. Int. Whal. Comm. Special Issue 15, pp. 565-571.

The detection and avoidance of gillnets by echolocating dolphins is examined by using the generalized sonar equation along with target strength values of nets and dolphin sonar detection data. Acoustic reflection data were obtained for several types of nets and associated gear by ensonifying them with simulated bottlenose dolphin sonar signals.. The results indicated most dolphins should be able to detect a monofilament gillnet at sufficiently long ranges to avoid entanglement. Reasons for entanglement are discussed.

Au, W.W.L. and P.E. Nachtigall. 1994. Dolphin Acoustics and Echolocation. Acoustical Bulletin, August-September Issue, 1994.

General article discussing sound production/reception and other aspects of echolocation in the bottlenose dolphin (Tursiops truncatus) and providing data on echolocation capabilities.

Au, W.W.L. 1995. Hot Topics in Animal Bioacoustics. (Abs.). Jour. Acoust. Soc. Am. 98 (5, Pt. 2): 2935.

Reports on recent bioacoustics research by the Navy, Air Force and others on a wide variety of species, including insects, birds, terrestrial mammals and whales.

Au, W.W.L., J.L. Pawloski, P.E. Nachtigall, M.E. Blonz, and R.C. Gisiner. 1995. Echolocation Signals and Transmission Beam Pattern of a False Killer Whale (Pseudorca crassidens). Jour. Acoust. Soc. Amer. 98 (1): 51-59.

The echolocation transmission beam pattern of a false killer whale was measured in the vertical and horizontal planes in the open waters of Kaneohe Bay, Oahu, Hawaii, while the whale performed a target discrimination task. Four types of signals, characterized by their frequency spectra, were measured.

Au, W.W.L., P.E. Nachtigall, and J.L. Pawloski. 1995. The Effects of the Acoustic Thermometry of Ocean Climate Signals on Dolphins and Small Whales. (Abs.). Jour. Acoust. Soc. Am. 98 (5, Pt. 2): 2940.

To address concerns of the possible effect of the ATOC signal on marine life, the hearing sensitivities of a false killer whale (Pseudorca crassidens) and a Risso’s dolphin (Grampus griseus) were measured behaviorally.

Au, W.W.L., P.E. Nachtigall and J.L. Pawloski. 1995. The Effects of the ATOC Signals on Dolphins and Small Whales. (Abs.) 11th Biennial Conf. on the Biology of Marine Mammals, p. 5.

See Au, Nachtigall and Pawloski, 1995, above.

Au, W.W.L. 1996. Acoustic Reflectivity of a Dolphin. Jour. Acoust. Soc. Am. 99 (6): 3844-3848.

See Au, 1994, above.

Au, W.W.L. and K. Banks. 1996. The Acoustics of Snapping Shrimp in Kaneohe Bay. (Abs.) Jour. Acoust. Soc. Am. 99 (4, Pt. 2): 2533.

Reports on study of Synalpheus paraneomeris, which are among the major contributors of biological noise in shallow bays, harbors and inlets. Their sounds can severely limit the use of underwater acoustics by humans, dolphins, whales and pinnipeds.

Au, W.W.L. 1997. Some Hot Topics in Animal Bioacoustics. Jour. Acoust. Soc. Am. 101 (5, Pt. 1): 2433-2441.

Discusses six bioacoustics studies on a wide variety of species, including two insects, manatees, elephant seals, dolphins and small whales. Notes the increasing interest in and importance of bioacoustics studies.

Au, W.W.L. 1997. Echolocation in Dolphins with a Dolphin-Bat Comparison. Bioacoustics. 8: 137-162.

Discusses the echolocation transmission and reception systems and target detection and discrimination capabilities of bottlenose dolphins, based on three specific experiments. Also provides a brief comparison between the bat and dolphin sonar system, including differences necessitated by substantial differences in the speed of sound through water versus air.

Au, W.W.L. 1997. The Acoustics of Snapping Shrimps. (Abs.) Jour. Acoust. Soc. Am. 101 (5, Pt. 2): 3032.

Reports on study of the crustaceans, which are among major contributors of biological noise in shallow waters of temperate and tropical regions. Reports on observation of a new low-frequency precursor signature.

Au, W.W.L., and D.L. Herzing. 1997. Measurement of the Echolocation Signals of the

Atlantic Spotted Dolphin Stenella frontalis in the Waters off the Grand Bahamas. (Abs.). Jour. Acoust. Soc. Am. 101 (5, Pt. 2): 3137-3138.

A three-hydrophone line array with a video camera attached was used to measure the echolocation signals of wild Atlantic Spotted Dolphins. On-axis signals typically had a bimodal spectrum with a low-frequency peak of 45-60 Hz. and high-frequency peak at 120-140 kHz.

Au, W.W.L., P.E. Nachtigall and J.L. Pawloski. 1997. Acoustic Effects of the ATOC

Signal (75 Hz, 195 dB) on Dolphins and Whales. Jour. Acoust. Soc. Am. 101 (5): 1973-1977.

To determine potential acoustic effects of ATOC on dolphins and whales, hearing sensitivity studies were conducted on a false killer whale and a Risso’s dolphin. Results indicate that with the source on the axis of the deep sound channel, ATOC signals will probably have minimal physical and physiological effects on cetaceans.

Au, W.W.L., and P.E. Nachtigall. 1997. Acoustics of Echolocating Dolphins and Small Whales. Marine and Freshwater Physiology and Behavior. 29: 127-162

Discusses the acoustic reception and transmission systems of dolphins, including auditory sensitivity, spectral analysis capabilities, directional hearing, and echolocation signals.

Awbrey, F. T., J. A. Thomas, and R. A. Kastelein. 1988. Low-Frequency Underwater Hearing Sensitivity in Belugas (Delphinapterus leucas). Jour. Acoust. Soc. Am. 84 (6): 2273-2275.

Sensitivity of three captive belugas was measured at octave intervals between 125 Hz and 8 kHz. Average thresholds at 8 kHz agreed with published data. Sensitivity decreased by approximately 11 dB per octave below 8 kHz.

Bastian, J., C. Wall, and C. L. Anderson. 1966. The Transmission of Arbitrary Environmental Information between Bottlenosed Dolphins. In: Animal Sonar Systems--Biology and Bionics, Vol. II, R.G. Busnel (ed.). Laboratoire de Physiologie Acoustique, Jouy-en-Josas 78, France, pp. 803-873.

Bastian, J., C. Wall, and C. L. Anderson. 1968. Further Investigation of the Transmission of Arbitrary Information Between Bottlenosed Dolphins. NUWC TP 109, 40 pp.

The above two papers describe studies designed to ascertain if one dolphin could, by acoustic signals, "tell" another, partitioned from the first, to push one or the other of two paddles. After training, the animals performed correctly, but analysis of recordings indicated that they were responding to self-taught cues, with no comprehension of the task.

Brill, R. L., and P. J. Harder. 1989. The Effects of Sound Attenuation at the Lower Jaw on the Emitted Signals of an Echolocating Dolphin (Tursiops truncatus) (Abs.). Eighth Biennial Conf. on the Biology of Marine Mammals, Pacific Grove, CA., p. 8.

See Brill and Harder, 1991, below.

Brill, R. L., and P. J. Harder. 1991. The Effects of Attenuating Returning Echolocation Signals at the Lower Jaw of a Dolphin (Tursiops truncatus). Jour. Acoust. Soc. Am. 89 (6): 2851-2857.

Reports data indicating that a neoprene hood placed over the lower jaw of a bottlenosed dolphin did not affect the emission of useful echolocation signals and that the dolphin exercised control over click repetition rates and interclick intervals. The results support the theory that echolocation signals are emitted from a site above the line of the gape of the mouth and returning echoes are best received along the lateral sides of the dolphin’s lower jaw.

Brill, R.L., J.L.Pawloski, D.A. Helweg, P.W.B. Moore, and W.W.L. Au. 1991. Shape

Discrimination and Signal Characteristics of an Echolocating False Killer Whale (Pseudorca crassidens). (Abs.) Ninth Biennial Conf. on the Biology of Marine Mammals.

This study demonstrated the false killer whale's ability to discriminate between different targets using biosonar and investigated the whale's emitted signals for changes related to test conditions. The whale's overall performance was comparable to that of echolocating bottlenose dolphins (Tursiops truncatus). The data further suggested that the whale relied on cues of target shape and strength, that changes in signal parameters were task related, and that click decreases in click repetition rates were associated with learning experience.

Brill, R.L., J.L. Pawloski, D.A. Helweg, P.W.B. Moore, and W.W. Au . 1991. Target

Detection, Shape Discrimination, and Signal Characteristics of an Echolocating False Killer Whale (Pseudorca crassidens) (Abs.). Ninth Biennial Conf. on the Biology of Marine Mammals, Chicago, IL, Dec. 5-9, 1991.

See Brill et al., 1991 (above).

Brill, R.L., J.L. Pawloski, D.A. Helweg, P.W.B. Moore, and W.W.L. Au. 1992. Target Detection, Shape Discrimination, and Signal Characteristics of an Echolocating False Killer Whale (Pseudorca crassidens). Jour. Acoust. Soc. Am. 89:2851-2857.

Brill, R.L., J.L. Pawloski, D.A. Helweg, P.W.B. Moore, and W.W.L. Au. 1992. Target Detection, Shape Discrimination, and Signal Characteristics of an Echolocating False Killer Whale (Pseudorca crassidens). Jour. Acoust. Soc. Am. 92: 1324-1330

See Brill et al., 1991 (above).

Bullock, T. H., S. H. Ridgway, and N. Suga. 1971. Acoustically Evoked Potentials in Midbrain Auditory Structures in Sea Lions (Pinnipedia). Z. vergl. Physiologie 74: 372-387.

Electrophysiological experiments were conducted to determine neural response to different types of sounds. The results could not settle the question as to whether sea lions employ echolocation, but they indicated lack of specialization for the types of sounds bats and porpoises use.

Bullock, T. H., and S. H. Ridgway. 1972. Neurophysiological Findings Relevant to Echolocation in Marine Animals. In: Animal Orientation and Navigation, S.R. Galler et al. (eds). NASA Pub. SP-262, pp. 373-395.

A review.

Bullock, T. H., and S. H. Ridgway. 1972. Evoked Potentials in the Central Auditory System of Alert Porpoises to Their Own and Artificial Sounds. Jour. of Neurobiology 3 (1): 79-99.

Among other findings it was noted that high-intensity clicks often evoked quite modest potentials, while a much weaker click gave maximum potentials. This suggested that differences in click composition are quite important to a porpoise.

Caldwell, M. C., D. K. Caldwell, and W. E. Evans. 1966. Sounds and Behavior of Captive Amazon Dolphins, Inia geoffrensis. Contributions in Science, Los Angeles County Museum, No. 108, 24 pp.

Inia emits pulsed phonations that could be used for echolocation. The freshwater dolphins were not fearful of strange objects (as Tursiops usually is) and exhibited curiosity and playfulness.

Carder, D. A., and S. H. Ridgway. 1983. Apparent Echolocation by a Sixty-Day-Old Bottlenosed Dolphin, Tursiops truncatus. (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): S74.

Squeals were heard about 10 seconds after birth and whistlelike calls soon after, but high-frequency pulses, with head-scanning movements, were not noticed prior to 60 days.

Carder, D. A., and S. H. Ridgway. 1990. Auditory Brainstem Response in a Neonatal Sperm Whale, (Physeter spp.) Jour. Acoust. Soc. Am. 88 (Suppl. 1): S4.

The auditory brainstem response (ABR) was recorded from suction cup sensors placed on the whale’s head. Responses were obtained from clicks with peak frequencies as high as 60 kHz. The characteristics of the whale ABR are described. This is the first such information from any great whale species.

Carder, D., S. Ridgway, B. Whitaker and J. Geraci. 1995. Hearing and Echolocation in a Pygmy Sperm Whale Kogia. 11th Biennial Conf. on the Biology of Marine Mammals, Orlando, FL, Dec. 14-18, p. 20.

Reports on study of hearing and echolocation of a beached Kogia at the Baltimore Aquarium. Recordings of evoked potential, hearing, and echolocation pulses, including echolocation during pursuit of live fish, showed peak frequencies of 120 to 130 kHz. The hearing assessment was part of a physical exam prior to release back into the Atlantic Ocean. Auditory responses showed sensitivity in the same high-frequency area (100-150 kHz) as the echolocation pulses.

Ceruti, M. G., P. W. B. Moore, and S. A. Patterson. 1983. Peak Sound Pressure Level and Spectral Frequency Distributions in Echolocation Pulses of Atlantic Bottlenosed Dolphins (Tursiops truncatus). (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): S73.

Peaks in the average bimodal pulse spectrum occurred at 60 and 135 kHz or beyond, while the average unimodal pulse spectrum peaked at 120 kHz. Abstract includes other findings.

Ceruti, M. G., and W. W. L. Au. 1983. Microprocessor-based System for Monitoring a Dolphin’s Echolocation Pulse Parameters. Jour. Acoust. Soc. Am. 73 (4): 1390-1392.

Describes development of an on-line data acquisition system including a device for measuring the frequency spectrum of transient pulses between 30 and 135 kHz and discusses applications of the system in dolphin echolocation experiments.

Cummings, W. C., P. O. Thompson, and R. C. Cook. 1967. Sound Production of Migrating Gray Whales (Eschrichtius gibbosus Erxleben). (Abs.) Jour. Acoust. Soc. Am. 44 (5):1211.

Abstract of a paper reporting low-frequency moaning sounds from migrating gray whales.

Cummings, W. C., P. O. Thompson, and R. D. Cooke. 1968. Underwater Sounds of Migrating Gray Whales (Eschrichtius glaucus Cope). Jour. Acoust. Soc. Am. 44 (5):1278-1281.

Includes methods, results, and discussion of work done on sound production of gray whales. Three categories of sounds range in frequency from 15 to 305 Hz at source levels up to 52 dB re 1 microbar at 1 yard. New findings concerning gray whale behavior are presented.

Cummings, W. C., and L. A. Philippi. 1970. Whale Phonations in Repetitive Stanzas. NUC TP 196, 4 pp.

Recordings of low-frequency sounds from what were probably right whales revealed very similar stanzas lasting 11 to 14 minutes. Stanzas were repeated every 8 to 10 minutes.

Cummings, W. C., and P. O. Thompson. 1971. Underwater Sounds from the Blue Whale (Balaenoptera musculus). Jour. Acoust. Soc. Am. 50 (4, Pt. 2):1193-1198.

Powerful, three-part sounds lasting about 36.5 seconds and ranging in frequency from 12.5 to 200 Hz were recorded from blue whales off the coast of Chile. Their "moanings," estimated to be 188 dB re 1 u N/m2 (88 dB re 1 ubar) at 1 meter, are the most powerful sustained utterances known from whales or any other living source.

Cummings, W. C., J. F. Fish, P. O. Thompson, and J. R. Jehl, Jr. 1971. Bioacoustics of Marine Animals of Argentina, R/V Hero cruise 71-3. Antarctic Jour. of the U.S. 6 (6):266-268.

Describes sounds of cetaceans and pinnipeds recorded along the coast of Argentina.

Cummings, W. C., and J. F. Fish. 1971. Bioacoustics of Cetaceans. Alpha Helix Research Program, 1971, U. of Calif., San Diego, p. 29.

Discusses the likelihood that 20-Hz signals are produced by the blue whale.

Cummings, W. C., and P. O. Thompson. 1971. Gray whales (Eschrichtius robustus) Avoid the Underwater Sounds of Killer Whales. Fish. Bull. 69 (3):525-530.

Recorded sounds of killer whales were transmitted underwater to gray whales as the latter were migrating south to Baja California. In most instances the gray whales swam away from the sound source. Pure-tone sounds and random noise had no effect.

Cummings, W. C., and P. O. Thompson. 1971. Bioacoustics of Marine Mammals: R/V Hero Cruise 7-3. Antarctic Jour. of the U.S. 6 (5): 158-160.

Brief account of the cruise of the NSF research vessel Hero from Punta Arenas to Valparaiso, Chile. Sounds of blue whales as well as South American fur seals and sea lions were recorded. No underwater vocalizations were detected from Guadalupe fur seals.

Cummings, W. C., J. F. Fish, and P. O. Thompson. 1972. Sound Production and Other Behavior of Southern Right Whales (Eubalaena glacialis). Trans., San Diego Soc. Nat. Hist. 17 (1):1-13.

The underwater sounds were recorded in Golfo San Jose, Argentina, in late June and early July 1971. The most common was a belch-like utterance with most energy below 500 Hz. The whales also produced two kinds of "moans" and miscellaneous other sounds. Observed behavior suggested bottom feeding.

Diercks, H. J., and W. E. Evans. 1969. Delphinid Sonar: Pulse Wave and Simulation Studies. NUC TP 175, 84 pp.

A series of reports, primarily by Applied Research laboratories, U. of Texas, on analysis of the dolphin’s emitted signal forms and simple target-echo forms, and a similar consideration of simulated pulses and their echoes. The data are largely preliminary to more detailed analyses.

Diercks, H. J., R. T. Trochta, C. F. Greenlaw, and W. E. Evans. 1971. Recording and Analysis of Dolphin Echolocation Signals. Jour. Acoust. Soc. Am. 49 (6, Pt. 1):1729-1732.

Describes techniques of recording sonar signals by transducers attached by small suction cups to a porpoise’s head and body, with examples of data obtained.

Dolphin, W., W.W.L Au, D. Carder, M. Beeler, P.E. Nachtigall, J.L. Palowski and S.H. Ridgway. 1994. Modulation Rate Transfer Functions to Low-Frequency Carriers in Three Species of Cetaceans. Jour. Acoust. Soc. Am. 96:

A new evoked potential technique was developed for hearing testing in Pseudorca, Tursiops, and Delphinapterus.

Evans, E. C. III, and K. S. Norris. 1988. On the Evolution of Acoustic Communication Systems in Vertebrates. Part II: Cognitive Aspects. In: Animal Sonar Processes and Performance, P.E. Nachtigall and P.W.B. Moore (eds.). Plenum Press, New York, pp.771-681.

Discusses cognitive aspects of acoustic communication as a continuation of Norris and Evans, 1988. The development of processes to bypass innate limitations of the central nervous system is reviewed. Communication heirarchies and cognitive aspects of language and echolocation are also reviewed.

Evans, W. E. 1967. Vocalization Among Marine Mammals. In: Marine Bio-Acoustics, Vol. II, W.H. Tavolga (ed.). Pergamon Press, Elmsford, NY, pp. 159-186.

An account of the kinds of sounds produced by marine mammals with discussion of what is known regarding their significance.

Evans, W. E. 1967. Discussion of Mechanisms of Overcoming Interference in Echolocating Animals, by A. D. Grinnell. In: Animal Sonar Systems - Biology and Bionics, Vol. 1. R. G. Busnel (ed.). Laboratoire de Physiologie Acoustique, Jouy-en-Josas 78, France, pp. 495-503.

Discusses some of the possible interference factors in biological echolocation in the aquatic environment.

Evans, W. E., and B. A. Powell. 1967. Discrimination of Different Metallic Plates by an Echolocating Delphinid. In: Animal Sonar Systems - Biology and Bionics, Vol. 1. R. G. Busnel (ed.). Laboratoire de Physiologie Acoustique, Jouy-en-Josas 78, France, pp. 366-383.

A blindfolded bottlenosed dolphin was found to be capable of discriminating a 30-cm diameter target (paddle) of 0.22-cm copper plate with echolocation when paired with targets of other materials, including aluminum plate.

Evans, W. E., and J. Bastian. 1969. Marine mammal communication: social and echological factors. In: The Biology of Marine Mammals, H. T. Andersen (ed.). Academic Press, San Diego, CA, pp. 425-475.

While many sounds made by marine mammals have social and communicative significance, there is no evidence porpoises (regarding which there has been much speculation) possess a language comparable to the human language.

Evans, W. E. 1973. Echolocation by Marine Delphinids and One Species of Freshwater Dolphin. Jour. Acoust. Soc. Am. S4 (1):191-199.

A brief summary of the state of knowledge of echolocation of small-toothed whales.

Evans, W. E., and P. F. A. Maderson. 1973. Mechanisms of Sound Production in Delphinid Cetaceans: A Review and Some Anatomical Considerations. Amer. Zool. 13:1205-1213.

Review of earlier literature describing possible sites of sound-producing mechanisms, with a discussion of the morphology of the nasal sac system. It is concluded that theories implicating the nasal sac system in sound production are supported by certain anatomical specializations adjacent to the tissues of this system.

Fish, J. F., and H. E. Winn. 1969. Sounds of Marine Mammals. In: Encyclopedia of Marine Resources, F. E. Firth (ed.). Van Nostrand Reinhold Co., New York, pp. 649-655.

Summarizes important contributions to the knowledge of marine mammal sound production and hearing. Includes the major papers up to 1967.

Fish, J. F., and J. S. Vania. 1971. Killer Whale (Orcinus orca) Sounds Repel White Whales. Fish. Bull. 69 (3):531-535.

A study conducted to determine if white whales migrating up the Kvichak River in Alaska which feed on salmon smolt could be turned back by underwater transmission of killer whale sounds. The playback of killer whale sounds was found to be an effective way to keep white whales out of the river.

Fish, J. F., J. L. Sumich, and G. E. Lingle. 1974. Sounds Produced by the Gray Whale (Eschrichtius robustus). Mar. Fish. Rev. 36 (4): 38-48.

Describes the sounds recorded from a young gray whale in captivity and sounds recorded in the vicinity of the whale when it was returned to the ocean.

Fish, J. F., C. S. Johnson, and D. K. Ljungblad. 1976. Sonar Target Discrimination by Instrumented Human Divers. Jour. Acoust. Soc. Am. S9 (3):602-606.

Human divers, instrumented with "bionic" sonar equipment based on the porpoise echolocation system and presented with targets earlier used in porpoise sonar discrimination experiments, made scores as good as or better than the porpoises.

Fish, J. F., and C. W. Turl. 1976. Acoustic Source Levels of Four Species of Small Whales. NUC TP 547, 14 pp.

Absolute sound pressure level measurements were made at sea on herds of the common dolphin, pilot whale, bottlenosed dolphin, and northern right whale.

Floyd, R. W. 1980. Models of Cetacean Signal Processing. In: Animal Sonar Systems, R.G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 616-623.

A review in which the apparent merits and deficiencies of various models of signal processing are discussed, with suggestions for future experiments.

Floyd, R. W. 1988. Biosonar Signal Processing Applications. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 773-783.

The performance of some existing man-made sonars and dolphin sonar is compared. The differences between the two are discussed and methods for improving man-made sonars are described.

Floyd, R. W. and J. E. Sigurdson. 1996. Autonomous Detection and Classification of Bottom Objects with Multi-Aspect Sonar. Symposium on Technology and the Mine Problem, U. S. Naval Postgraduate School, Monterey, CA.

Describes test of a mobile 40-beam multiple-aspect sonar on a VSW field with

many small bottom-targets. Novel automated signal analysis methods successfully detected all targets with a very low false-alarm rate and extracted a file of multiple-aspect echo returns for each target. Classification of detected targets was based on highlight separations and distributions of reflected energy.

Friedl, W. A., and P. O. Thompson. 1981. Measuring Acoustic Noise Around Kahoolawe Island. (Abs.) Jour. Acoust. Soc. Am. 70 (Suppl. 1): S84.

Seven sonobuoys were monitored for seven hours from a P-3 aircraft during gunnery exercises by a Navy ship north of Kahoolawe. Humpback whale locations and behavior were also monitored. Whales were observed swimming, lying still, diving, surfacing, breeching, and bobtailing. Movements and activities of the whales could not be related to any airborne, surface, or subsurface stimuli.

Friedl, W. A., and P. O. Thompson. 1981. Measuring Acoustic Noise Around Kahoolawe Island. NOSC TR 732, 15 pp.

See Friedl and Thompson, 1981, above.

Gales, R. S. 1966. Pickup, Analysis, and Interpretation of Underwater Acoustic Data. In: Whales, Dolphins, and Porpoises, K. S. Norris (ed.). Univ. of Calif. Press, Berkeley.

Discusses instrumentation used for recording underwater sounds and presents analyses of a variety of cetacean sounds.

Gales, R. S., S. E. Moore, W. A. Friedl, and J. Rucker. 1987. Effects of Noise of a Proposed Ocean Thermal Energy Conversion Plant on Marine Animals - A Preliminary Report. (Abs.) Jour. Acoust. Soc. Am.. 82 (Suppl. 1): S98.

Discusses likely perception and behavioral responses of cetaceans and fishes to predicted noise from a 40-Mw. OTEC plant on Oahu, Hawaii.

Green, R. F., S. H. Ridgway, and W. E. Evans. 1980. Functional and Descriptive Anatomy of the Bottlenosed Dolphin Nasolaryngeal System with Special Reference to the Musculature Associated with Sound Production. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 199-238.

Detailed anatomical information with reference to external landmarks to facilitate the use of electromyographic techniques in determining activity of specific muscles used in sound production.

Green, D.M., H. DeFerrari, D. McFadden, J. Pearse, A. Popper, W.J. Richardson, S.H. Ridgway and P. Tyack. 1994. Low-Frequency Sound and Marine Mammals: Current Knowledge and Research Needs. Ocean Studies Board, Commission on Geosciences, Environment, and Resources, National Research Council, Washington, DC, 97 pp.

This report evaluates potential threats to marine mammals from low-frequency sound in the ocean. Suggestions are made for research to answer questions of environmental concern.

Hall, J. D., and C. S. Johnson. 1972. Auditory Thresholds of a Killer Whale (Orcinus orca) Linnaeus. Jour. Acoust. Soc. Am. 51(2, Pt. 2):515-517.

Using operant conditioning techniques, an audiogram was obtained for a killer whale for frequencies between 500 Hz and 31 kHz. Greatest sensitivity was observed at 15 kHz, with upper limit of hearing at 32 kHz.

Hammer, C. E., and W. W. L. Au. 1978. Target Recognition via Echolocation by an Atlantic Bottlenosed Dolphin (Tursiops truncatus). (Abs.) Jour. Acoust. Soc. Am. 64 (Suppl. 1): S87.

Target-recognition behavior as a function of target composition and internal structure was investigated using cylindrical hollow aluminum and solid coral rock targets for baseline data. Experiments were then conducted to determine the critical characteristic for target recognition.

Hammer, C. E., and W. W. L. Au. 1980. Porpoise Echo-recognition: An Analysis of Controlling Target Characteristics. Jour. Acoust. Soc. Am. 68 (5):1285-1293.

After baseline performance was established, a two-alternative, forced-choice method was used with two hollow aluminum and two coral rock cylinders (standard targets) probe targets. The probe target results indicated that the bottlenosed dolphin had learned to recognize the echo characteristics of the aluminum standards and differentiated other targets on that basis.

Harley, H.E., M.J. Xitco, and H.L. Roitblat. 1995. Echolocation, Cognition and the Dolphin’s World. In: Sensory Systems of Aquatic Mammals, R.A. Kastelein, J.A. Thomas and P.E. Nachtigall (eds.). DeSpil Publishers, Woerden, The Netherlands.

Discusses studies investigating the flexibility with which a dolphin can use echoic information. Studies suggest a pair of dolphins can share object information received through a single set of echoes. The flexibility of such representations may impact delphinid social behavior.

Harley, H., H.L. Roitblat, and P.E. Nachtigall. 1996. Object Representation in the Bottlenosed Dolphin (Tursiops truncatus): Integration of Visual and Echoic Information. Jour. Exper. Psych.: Animal Behavior Processes. 22 (2), 164-174.

A dolphin performed a 3-alternative matching-to sample task in different modality conditions. The dolphin successfully matched familiar objects in the cross-modal (vision-echolocation, echolocation-vision) conditions, suggesting that the dolphin has an object-based representational system.

Helweg, D.A., H.L. Roitblat, and P.E. Nachtigall. 1993. Object Constancy in Dolphin Echolocation. (Abs.). Tenth Biennial Conf. on the Biology of Marine Mammals, Society for Marine Mammalogy, Galveston, TX, Nov. 12-16.

Examines dolphin representation of objects they echolocate. Discusses experiment to investigate whether they construct an aspect-independent cognitive representation containing structural (shape) information or an acoustically based one from echoes.

Helweg, D.A., H.L. Roitblat, P.E. Nachtigall, W.W.L. Au, and R.J. Irwin. 1996. Discrimination of Echoes from Aspect Dependent Targets by a Bottlenose Dolphin and Human Listeners. In: Sensory Systems of Aquatic Mammals, R. A. Kastelein, J.A. Thomas, and P.E. Nachtigall (eds.). pp. 129-136.

Aspect-dependent targets (such as cubes) produce different echoes at different orientations, which may impede recognition. This study suggests an Atlantic bottlenose dolphin may have formed aspect-invariant representations of targets, rather than representations of the specific acoustic qualities of the echoes. This may require integration of changes in echo characteristics such as amplitude across successive echoes.

Helweg, D.A., W.W.L. Au, H.L. Roitblat and P.E. Nachtigall. 1996. Acoustic Basis for Recognition of Aspect-Dependent Three-Dimensional Targets by an Echolocating Bottlenose Dolphin. Jour. Acoust. Soc. Am. 99 (4): 2409-2420.

A blindfolded Atlantic bottlenose dolphin (Tursiops truncatus) learned to match aspect-dependent three-dimensional targets (such as cubes) at haphazard orientations, although with some difficulty. Results suggested that the dolphin recognized the targets using a multidimensional representation containing amplitude and spectral information and that dolphins can form stable representations of targets regardless of orientation based on varying sensory properties.

Helweg, D.A., H.L. Roitblat, P.E. Nachtigall and M.J. Hautus. 1996. Recognition of Aspect-Dependent Three-Dimensional Objects by an Echolocating Atlantic Bottlenose Dolphin. Jour. Exper. Psych.: Animal Behavior Processes. 22: 19-31.

The study examined the ability of an echolocating bottlenose dolphin (Tursiops truncatus) to recognize aspect-dependent objects, such as cubes, which produce acoustically different echoes at different orientations. The dolphin recognized the objects even though they were free to rotate and sway. The results show dolphins can use varying acoustic properties to recognize constant objects and suggest that aspect-independent representations may be formed by combining information gleaned from multiple echoes.

Herald, E. S. 1969. A Field and Aquarium Study of the Blind River Dolphin (Platanista gangetica). NUC TP 153, 62 pp.

Blind river dolphins ("susu") from the Indus River of Pakistan swim on their sides. Presumably this permits a lateral echolocation sweep of the bottom. Underwater sound emissions of pulse trains are produced continuously.

Jacobs, D. W., and J. D. Hall. 1972. Auditory Thresholds of a Freshwater Dolphin (Inia geoffrensis). Blainville. Jour. Acoust. Soc. Am. 51 (2, Pt. 2):530-533.

An Amazon River dolphin was conditioned to respond to pure tones by pushing a lever. By this method an audiogram was obtained for frequencies between 1.0 and 105 kHz. Greatest sensitivity was found between 75 and 90 kHz, with effective upper limit of hearing at 105 kHz.

Johnson, C. S. 1967. The Possible Use of Phase Information in Target Discrimination, and the Role of Pulse Rate in Porpoise Echoranging. In: Animal Sonar Systems - Biology and Bionics, Vol. 1, R. G. Busnel (ed.). Laboratoire de Physiologie Acoustique Jouy-en-Josas 78, France, pp. 384-398.

A discussion of the paper by Evans and Powell, 1967. On the basis of theoretical considerations there are phase differences in reflected pulse shapes which may be utilized by the porpoise. An analysis of pulse rate versus range and time indicates the decreasing pulse rate is based on time before target contact rather than range.

Johnson, C. S. 1968. Sound Detection Thresholds in Marine Mammals. In: Marine BioAcoustics, Vol. 2, W. N. Tavolga (ed.). Pergamon Press, Elmsford, NY, pp.247-260.

By a behavioral response method, an audiogram for a bottlenosed porpoise was obtained over a frequency range from 75 Hz to 150 kHz. Maximum sensitivity was found at about 50 kHz.

Johnson, C. S. 1968. Relation Between Absolute Threshold and Duration-of-Tone Pulses in the Bottlenosed Porpoise. Jour. Acoust. Soc. Am. 43 (4):757-763.

This study indicated that the porpoise, in detecting pure tone stimuli, integrated the acoustic energy in essentially the same way that humans do.

Johnson, C. S. 1969. Masked Tonal Thresholds in the Bottlenosed Porpoise. Jour. Acoust. Soc. Am. 44 (4): 965-967.

An analysis of hearing thresholds when a narrowband of frequencies is masked by broadband noise.

Johnson, C. S. 1971. Auditory Masking of One Pure Tone by Another in the Bottlenosed Porpoise. Jour. Acoust. Soc. Am. 49 (L): 1317.

Pure-tone masking-tone thresholds were obtained for a bottlenosed porpoise. Using a masking-tone frequency of 70 kHz and masking levels at 40 and 80 dB above threshold, the shapes of the masking curves were similar to those obtained from human subjects at much lower frequencies.

Johnson, C. S. 1979. Thermal-noise Limit in Delphinid Hearing. NOSC TD 270, 4 pp.

In quiet tanks, thermal noise is the dominant sound source above 50 kHz. Evidence indicates that in the frequency range above 50 kHz cetacean auditory thresholds are limited by thermal noise.

Johnson, C. S. 1980. Important Areas for Future Cetacean Auditory Study. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 515-518.

Discusses three apparent anomalies in experimental results on cetacean hearing.

Johnson, C. S. 1986. Dolphin Audition and Echolocation Capacities. In: Dolphin Cognition and Behavior, R. J. Schusterman, J. A. Thomas, and F. G. Wood (eds.). Lawrence Erlbaum Associates, Hillsdale, NJ, pp. 115-136.

A review. Includes ear anatomy and transduction mechanisms, auditory thresholds, echolocation sound production, and theoretical echolocation models.

Johnson, C. S. 1988. A Brief History of Bionic Sonars. In: Animal Sonar Processes and Performances, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 769-771.

A brief description of the U.S. Navy’s attempts to build bionic sonars.

Johnson, C. S., M. W. McManus, and D. Skaar. 1989. Masked Tonal Hearing Thresholds in the Beluga Whale. Jour. Acoust. Soc. Am. 85(6):2651-2654.

Beluga critical ratios were about 3 dB lower than those reported for bottlenosed dolphins. Reported critical ratios for dolphins are not significantly different from beluga ratios at higher frequencies.

Johnson, C. S. 1991. Hearing Thresholds for Periodic 60-Hz Tone Pulses in the Beluga Whale. Jour. Acoust. Soc. Am. 89 (6):2996-3001.

Masked thresholds were measured with various pulse lengths and repetition times. Unlike the human data, the whales’ integration times were found to vary almost directly with time.

Johnson, R. A. 1980. Energy Spectrum Analysis in Echolocation. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish, (eds.). Plenum Press, New York, pp. 673-693.

Discusses object detection, distance estimation, and object identification and how they may be accomplished in energy spectrum analysis as an alternative to correlation processing in the time-domain sense.

Johnson, R. A., P. W. B. Moore, M. W. Stoermer, J. L. Pawloski, and L. C. Anderson. 1988. Temporal Order Discrimination within the Dolphin Critical Interval. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 317-322.

Reports results on experiments to determine the ability of a dolphin to detect the difference in arrival order for appropriate stimuli and investigate the cues available to discriminate the stimuli. This paper concludes that the dolphin has the ability to discriminate the temporal order of click-pairs within the critical interval, and although the analysis in the time domain might explain this ability, the results support the hypothesis that the analysis of rippled spectra may be an important function of dolphin audition.

Kadane, J., R. H. Penner, W. W. L. Au, and R. W. Floyd. 1980. Microprocessors in Collection and Analysis of Tursiops truncatus Echolocation Data. (Abs.) Jour. Acoust. Soc. Am. 68 (Suppl. 1): S8.

Describes the equipment used to collect and analyze a variety of parameters of echolocation signals emitted by a dolphin in various detection tasks.

Kadane, J,, and R. H. Penner. 1983. Range Ambiguity and Pulse Interval Jitter in the Bottlenosed Dolphin. Jour. Acoust. Soc. Am. 74 (3): 1059-1061.

In pulse-mode sonar systems which use range gating, range ambiguity can be caused by echoes from objects at multiple distances returning simultaneously. A bottlenosed dolphin was found to vary consecutive interpulse intervals enough to eliminate this form of range ambiguity.

Lammers, M.O. and W.W.L. Au. 1996. Broadband Recording of Social Acoustic Signals of the Hawaiian Spinner and Spotted Dolphins. (Abs.). Jour. Acoust. Soc. Am. 100 (4, Pt. 2): 2609.

Signals from Hawaiian spinner and spotted dolphins up to 55 kHz in frequency were recorded using a new technique. Digitizing signals directly into a laptop computer through an analog/digital converter allowed recording and study of sonic and ultrasonic components of the whistles and burst pulses of the dolphins.

Lang, T. G., and H. A. P. Smith. 1965. Communication Between Dolphins in Separate Tanks by Way of an Acoustic Link. Science 150:1839-1843.

Alternating exchange of different kinds of whistles occurred between two dolphins.

Leatherwood, J. S., R. A. Johnson, D. K. Ljungblad, and W. E. Evans. 1977. Broadband Measurements of Underwater Acoustic Target Strengths of Panels of Tuna Nets. NOSC TR 126, 18 pp.

Target strengths of sample panels of tuna nets of three different mesh sizes were determined. All panels produced sufficiently strong returns to allow porpoises to detect them acoustically.

Ljungblad, D. K., and J. S. Leatherwood. 1979. Sounds Recorded in the Presence of Adult and Calf Bowhead Whales (Balaena mysticetus). NOSC TR 420, Rev. 1, 108 pp.

Low-frequency sounds, identified as Type A and Type B, were recorded. Type A sounds were of brief duration, with fundamental frequency ranging from 50 to 580 Hz and few or no harmonics. Type B sounds were longer, the fundamental frequency ranged from 100 to 195 Hz, and they were rich in harmonics.

Ljungblad, D. K., J. S. Leatherwood, and M. E. Dahlheim. 1980. Sounds Recorded in the Presence of an Adult and Calf Bowhead Whale. Mar. Fish. Rev. 42(9-10):86-87.

Modified version of Ljungblad and Leatherwood 1979.

Ljungblad, D. K., P. D. Scoggins, and W. G. Gilmartin. 1982. Auditory Thresholds of a Captive Eastern Pacific bottlenosed Dolphin, Tursiops spp. Jour. Acoust. Soc. Am. 72 (6):1726-1729.

Hearing thresholds were tested using behavioral response techniques. The animal responded to signals ranging from 2 to 135 kHz, but not to higher frequencies. Range of greatest sensitivity was between 25 and 70 kHz, with peak sensitivities at 25 and 50 kHz.

Ljungblad, D. K., P. O. Thompson, and S. E. Moore. 1982. Underwater Sounds Recorded from Migrating Bowhead Whales (Balaena mysticetus) in 1979. Jour. Acoust. Soc. Am. 71 (2):477--482.

Sounds were recorded from sonobuoys during spring and fall migrations. Most sounds at both times were low-frequency (below 800 Hz) moans, simple or complex. Repetitive sequences were found only in the spring samples. High-frequency (to 4 kHz) trumpeting calls were recorded in the fall (but also occurred in the spring of 1981).

Marten, K., K. S. Norris, P. W. B. Moore, and K. A. Englund. 1988. Loud Impulse Sounds in Odontocete Predation and Social Behavior. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore, (eds.). Plenum Press, New York, pp. 567-579.

This paper discusses analysis of data to determine the extent of impact on loud impulse sounds during fish predation by odontocetes. The characteristics and source of impulse sounds are also discussed.

Martin, D. W., and W. W. L. Au. 1980. Aural Discrimination of Target Echoes in White Noise by Human Observers Using Broadband Sonar Pulses. (Abs.) Jour. Acoust.Soc. Am. 68 (Suppl. 1): 557.

Recordings of target echoes obtained from dolphin-like pulses directed at hollow aluminum and glass cylinders and one solid aluminum cylinder were played back to human subjects at 1/50 of the original rate. The average 75 percent correct response threshold occurred at different signal-to-noise ratios, with the lowest SNR for the solid target.

Martin, D. W., and W. W. L. Au. 1983. Auditory Detection of Broadband Sonar Echoes from a Sphere in White Noise. (Abs.) Jour. Acoust. Soc. Am. 73 (Suppl. 1): 591.

The ability of two human subjects to detect time-stretched broadband sonar echoes from a water-filled stainless-steel sphere in white noise was tested. At stretch factors of 75 and 50, the subjects performed better than dolphins did with unaltered echoes.

Martin, D. W., and W. W. L. Au. 1986. Broadband Sonar Classification Cues: An Investigation. NOSC TR 1123, 36 pp.

Sonar echo-discrimination experiments were conducted with human subjects to (1) measure their performance using echoes from geometric targets, (2) determine the acoustic cues used, (3) develop software algorithms to extract echo features similar to those used by humans, and (4) determine whether the features can be used for automatic target classification.

Martin, D. W., and W. W. L. Au. 1988. An Automatic Target Recognition Algorithm Using Time-Domain Features. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 829-833.

A technique to recognize broadband echoes from underwater targets is discussed. The technique used the envelope of the time-domain echoes with the time between highlights and the relative amplitude of highlights being the features used to describe targets. The ability of this technique to separate target echoes was tested for a noise-free condition and was found to perform well.

McCormick, J. G., E. G. Wever, J. Palin, and S. H. Ridgway. 1971. Sound Conduction in the Dolphin Ear. Jour. Acoust. Soc. Am. 48 (6):1418-1428.

By electrophysiological methods, the mechanisms and pathways of sound conduction in the dolphin ear were determined.

McCormick, J. G.. E. G. Wever, S. H. Ridgway, and J. Palin. 1980. Sound Reception in the Porpoise as it Relates to Echolocation. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 449-467.

A review of earlier work, with the addition of new information and arguments.

Moore, P. W. B. 1975. Underwater Localization of Click and Pulsed Pure-tone Signals by the California Sea Lion (Zalophus californianus). Jour. Acoust. Soc. Am. 57 (2): 406-410.

The ability of the sea lion to localize both pure tone and click sounds underwater is presented. The results are compared to previous studies on sea lions and seals.

Moore, P. W. B., and W. W. L. Au. 1975. Underwater Localization of Pulsed Pure Tones by the California Sea Lion (Zalophus californianus). Jour. Acoust. Soc. Am. 58 (3): 721-727.

The animal appeared to use time-difference cues for lower frequencies (0.5-16 kHz) and intensity-difference cues for higher frequencies (4-16 kHz). The minimum auditory angles for the lower frequencies were smaller than for the higher frequencies.

Moore, P. W. B., and R. J. Schusterman. 1977. Discrimination of Pure-Tone Intensities by the California Sea Lion. Jour. Acoust. Soc. Am. 60 (6):1405-1407.

The ability of the sea lion to discriminate tonal intensities was measured and compared to other mammals. The role of sound intensity difference in sea lion localization is also discussed. The experiment was directed at determining a theoretical ability suggested by earlier sea lion localization studies.

Moore, P. W. B., and R. J. Schusterman. 1978. Masked Pure Tone Thresholds of the Northern Fur Seal (Callorhinus ursinus). Jour. Acoust. Soc. Am. 64 (Suppl. 1A): S87.

Thresholds for two animals were determined at three continuous broadband masked noise levels at 2, 4, 8, 16 and 32 kHz. The critical ratio for both animals was calculated.

Moore, P. W. B. 1980. Cetacean Obstacle Avoidance. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 97-108.

A review, including early dolphin echolocation experiments and field observations.

Moore, P. W. B., and W. W. L. Au. 1981. Directional Hearing Sensitivity of the Atlantic Bottlenosed Dolphin (Tursiops truncatus) in the Vertical Plane. (Abs.) Jour. Acoust. Soc. Am. 70 (Suppl. 1): 585.

Maximum sensitivity for pure-tone frequencies of 30, 60, and 120 kHz occurred between 5 and 10 degrees above the midline of the mouth. Sensitivity dropped more sharply with increasing angle above the midline rather than below.

Moore, P. W. B., and W. W. L. Au. 1982. Masked Pure-Tone Thresholds of the Bottlenosed Dolphin (Tursiops truncatus) at Extended Frequencies. (Abs.) Jour. Acoust. Soc. Am. 70 (Suppl. 1): 542.

Response thresholds at two masking noise levels were obtained from 30 to 140 kHz. The critical ratio (CR), ratios of signal power to noise spectrum level, was calculated for both noise levels. A function relating CRs to frequency conformed with previous finding to 100 kHz, but results above 100 kHz, not previously determined, showed a sharp increase at 110 kHz, followed by a decline at 120 kHz.

Moore, P. W. B. and S. A. Patterson. 1983. Behavioral Control of Echolocating Source Level in the Dolphin (Tursiops truncatus). Fifth Annual Conf. on the Biology of Marine Mammals, Boston, MA.. 70 (4).

This report covers the training steps designed to teach a dolphin to generate echolocation signals that vary in frequency content and amplitude.

Moore, P. W. B., and W. W. L. Au. 1983. Critical Ratio and Bandwidth of the Atlantic Bottlenosed Dolphin (Tursiops truncatus). (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): 573.

Masked underwater pure-tone thresholds were obtained at test frequencies ranging from 30 to 140 kHz at two levels of broadband noise.

Moore, P. W. B., R. W. Hall, W. A. Friedl, and P. E. Nachtigall. 1984. The Critical Interval in Dolphin Echolocation: What is it? Jour. Acoust. Soc. Am. 76 (1):314-317.

In an active echolocation target detection task, the echolocation click from a bottlenosed dolphin triggered a short-sound-burst masking noise, from the target area, which could be adjusted from coincidence with the target echo to delays up to 700 ms. The animal’s detection performance, high at long delays, dropped to chance level for a 100-ms delay. This was seen as supporting the view that time separation pitch may be an analytic mechanism used by the dolphin to discern within-echo target attributes rather than for determining target range.

Moore, P. W. B., and D. A. Pawloski. 1987. Voluntary Control of Peak Frequency in Echolocation Emissions of Dolphin (Tursiops truncatus). (Abs.) Seventh Biennial Conf. on the Biology of Marine Mammals. Society of Marine Mammalogy, Miami, FL., p. 47.

Discusses experiments with a bottlenosed dolphin previously trained to shift its outgoing emitted source level and also trained to shift the peak frequency of its echolocation emissions.

Moore, P. W. B., and R. J. Schusterman. 1987. Audiometric Assessment of Northern Fur Seals (Callorhinus ursinus). Marine Mammal Science 3: 31-53.

The hearing thresholds for the Alaska fur seal in both air and underwater are presented and compared to other pinnipeds. This study defines hearing in fur seals.

Moore, P. W. B. 1988. Dolphin Echolocation and Audition. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 161-168.

A review of psychoacoustic data on bottlenosed dolphins presented or collected from 1980 to 1988, including data on critical interval, echolocation adaptability, and basic hearing parameters. Recommendations for future research are also outlined.

Moore, P. W. B. 1989. Investigations on the Control of Echolocation Pulses in the Dolphin. Fifth International Theriological Congress, Rome, Italy, August 22-29, 1989.

See Moore and Pawloski, 1990, below.

Moore, P. W. B., and D. A. Pawloski. 1990. Investigations on the Control of Echolocation Pulses in the Dolphin. In: Dolphin Sensory Processes, J.A. Thomas and R. Kastelein (eds.). Plenum Press, New York, pp. 305-316.

Summarizes a series of experiments to determine if the echolocation emission parameters of the dolphin were under voluntary control. The ability of the dolphin to control the source level and frequency content of the echolocation emission is discussed. Results from several experiments are presented.

Moore, P. W. B. 1991. Dolphin Psychophysics: Concepts for the Study of Dolphin Echolocation. In: Dolphin Societies: Methods of Study, K. Pryor and K. Norris (eds.). Univ. of Calif. Press, Berkeley.

A compendium of personal insights on the study of dolphin sensory systems along with basic explanations of the tools and techniques used to study dolphins.

Moore, P. W. B. 1991. Dolphin Psychophysics: Concepts for the Study of Dolphin Echolocation. In: Dolphin Societies: Discoveries and Puzzles, K. Pryor and K. Norris (eds.). University of California Press, Berkeley and Los Angeles, pp.365 - 382.

A chapter discussing various applications of traditional psychoacoustics procedures for exploring the dolphin's echolocation capability.

Moore, P. W. B, P.E. Nachtigall and H.L. Roitblatt. 1992. Classification of Biological Echolocation Signals. In: NRaD TD 2412, IR-IED 1992 Annual Report, p. 27-41.

A report of a three-year effort to develop and model the dolphin's echolocation strategy and target classification capability based on a match-to-sample discrimination paradigm.

Moore, P.W.B. and D.A. Pawloski. 1993. Interaural Time Discrimination in the Bottlenose Dolphin (Abs.) Jour. Acoust. Soc. Am. 94 (3, Pt. 2): 1829.

Reports on first behavioral measurements on interaural hearing abilities in the dolphin (Tursiops truncatus). Special "jawphones" were constructed to act as earphones to isolate and present signals to the dolphin. Results suggested the dolphin has a keen ability to discriminate interaural time differences, with capabilities superior to any mammal previously measured.

Moore, P.W.B, D.A. Pawloski, and L.Dankiewicz. 1995. Interaural Time and Intensity Difference Thresholds in the Bottlenose Dolphin (Tursiops truncatus). In: Sensory Systems of Aquatic Mammals, R.A. Kastelein, J.A. Thomas and P.E. Nachtigall (eds). De Spil, Woerden, Netherlands, pp.11-24.

The first measures of interaural hearing parameters for any marine mammal. Thresholds for interaural time and intensity differences are reported. Results indicate the dolphin is superior to land mammals in discriminating on-going time disparity and slightly better than humans in determining interaural intensity differences. Best frequencies for both thresholds occur at least one order of magnitude above traditionally reported thresholds.

Moore, P.W.B. and L.W. Bivens. 1995. The Bottlenose Dolphin: Nature’s ATD in SWMCM Autonomous Sonar Platform Technology. Autonomous Vehicles in Mine Countermeasures Symposium. Naval Postgraduate School, Monterey, CA, April 4-7, 1995.

Marine mammal systems of the Navy are discussed, including issues relating to the Navy's current and future plans for fleet enhancements.

Moore, S. E., D. K. Ljungblad, and D. R. Schmidt. 1984. Ambient, Industrial and Biological Sounds Recorded in the Northern Bering, Eastern Chukchi and Alaskan Beaufort Seas During the Seasonal Migrations of the Bowhead Whale (Balaena mysticetus) 1979-1982. SEACO, Inc. Report for the Minerals Management Service, U. S. Dept. Interior, 104 pp.

Recordings made during spring and fall bowhead whale migration were analyzed for ambient, industrial, and biological sound content. The effect of sea state, ice covering and depth on measured ambient levels indicates that sea state was the dominant correlate. When corrected for distance, highest industrial noise levels were measured from seismic airguns followed by pipe driving, large vessels, small vessels and aircraft. Seven bowhead and four gray whale call types are presented. Beluga and bearded seal sounds were also analyzed.

Moore, S.E. and S.H. Ridgway. 1995. Whistles Produced by Common Dolphin from the Southern California Bight. Aquatic Mammals. 21(1):55-63.

Compares the whistles of two common dolphins, Delphinus delphis, kept in San Diego with those of a wild herd of the same species off Southern California.

Moore, S. E. and S. H. Ridgway. 1996. Patterns of Dolphin Sound Production and Ovulation. Aquatic Mammals. 22 (3):175-184.

Sound production in two female common dolphins, Delphinus delphis, decreased during times when plasma progesterone levels were high concurrent with ovulation. It is suggested that total sound production might be useful in monitoring reproductive cycles.

Murchison, A. E. 1980. Detection Range and Range Resolution of Echolocating Bottlenosed Porpoise (Tursiops truncatus). In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 43-70.

The maximum detection ranges of two Tursiops were determined for two different spherical targets in open water. A third target was used to determine the effects of target depth (or nearness to the bottom) at maximum detection ranges.

Nachtigall, P. E., A. E. Murchison, and W. W. L. Au. 1978. Cylinder and Cube Shape Discrimination by an Echolocating Blindfolded Bottlenosed Dolphin. (Abs.) Jour. Acoust. Soc. Am. 64 (Suppl. 1): S87.

See Nachtigall et al., 1980, below.

Nachtigall, P. E., A. E. Murchison, and W. W. L. Au. 1980. Cylinder and Cube Shape Discrimination by an Echolocating Blindfolded Bottlenosed Dolphin. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 945-947.

The dolphin could discriminate the cylinder as its aspect was changed except when the flat top of the cylinder faced the animal. Acoustic examination of the targets failed to reveal consistent and obvious echo cues for the discrimination of shape, but replicated measurements of target strength for each target revealed differences in standard deviations that paralleled the performance of the animal.

Nachtigall, P. E. 1980. Odontocete Echolocation Performance on Object Size, Shape and Material. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 71-95.

A review.

Nachtigall, P. E. 1980. Bibliography of Echolocation Papers on Aquatic Mammals Published Between 1966 and 1978. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish, (eds.). Plenum Press, New York, pp. 1029-1069.

Lists 580 references, many from the Soviet literature.

Nachtigall, P. E., and S. A. Patterson. 1980. Echolocation Sameness-Difference Discrimination by the Atlantic Bottlenosed Dolphin (Tursiops truncatus) (Abs.) Jour. Acoust Soc. Am. 68 (Suppl. 1): S98.

A dolphin was trained to respond differently to two simultaneously presented stimulus objects, depending on whether they were identical or different. After development of the sameness-difference concept, novel stimuli were similarly presented, and following successful completion of this test, sensory modality transfer was also achieved when the animal was blindfolded with rubber eyecups.

Nachtigall, P. E., and P. W. B. Moore (eds.). 1988. Animal Sonar Processes and Performance. 862 pp. NATO ASI Series, Series A: Life Sciences. Vol. 156. Plenum Press, New York.

This volume presents the proceedings of a NATO Advanced Study Institute on Animal Sonar Systems held September 10-19, 1986 in Helsignor, Denmark. This was the third international meeting on biosonar and contributors presented their most recent works. Topics included: (1) Echolocation signals and their production, (2) Auditory systems of echolocating animals, (3) Performance of animal sonar systems, (4) Natural history of echolocation, (5) Echolocation and cognition, and (6) Echolocation theory and applications.

Nachtigall, P. E. 1989. Sounds of a Stranded Pygmy Sperm Whale (Kogia breviceps). (Abs.) European Association for Aquatic Mammals, Tenerife, Spain.

Description of recordings made of a pygmy sperm whale beached on the northeast shore of Oahu, Hawaii.

Nachtigall, P. E., W.W.L. Au, J.L. Pawloski, and P.W.B. Moore. 1995. Risso’s Dolphin (Grampus griseus) Hearing Thresholds in Kaneohe Bay, Hawaii. In: Sensory Systems of Aquatic Mammals, R.A. Kastelein, J.A. Thomas and P.E. Nachtigall (eds), De Spil, Woerden, Netherlands, pp 49-53.

The first audiogram for the Risso's dolphin is reported. Conduct of the study in the natural environment of Kaneohe Bay, Oahu, Hawaii, limited determination of relative peak sensitivity. Data allow comparison with audiograms of other animals, indicating the Risso’s dolphin apparently hears high frequencies like other odontocetes.

Nachtigall, P.E., W.W.L. Au and J.L. Pawloski. 1995. Low Frequency Hearing of Pseudorca crassidens and Grampus griseus. (Abs.) 11th Biennial Conf. on the Biology of Marine Mammals, p. 82.

Reports on measurement studies of underwater behavioral hearing thresholds for a false killer whale (Pseudorca crassidens) and a Risso’s dolphin (Grampus griseus). In contrast to previously demonstrated very sensitive hearing at higher frequencies, both animals showed very poor hearing at the lower frequencies.

Nachtigall, P.E., W.W.L. Au, and J. Pawloski. 1996. Low-Frequency Hearing in Three Species of Odontocetes. (Abs.). Jour. Acoust. Soc. Am. 100 (4, Pt. 2): 2611.

Low-frequency underwater hearing thresholds for pure-tone signals between 75 and 1600 Hz were determined for an Atlantic bottlenose dolphin, a false killer whale and a Risso’s dolphin, using behavioral measures. The animals showed relatively poor hearing at these lower frequencies.

Norris, K. S., and E. C. Evans III. 1988. On the Evolution of Acoustic Communication Systems in Vertebrates, Part I: Historical Aspects. In: Animal Sonar Processes and Performances, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 655-669.

The evolution of vertebrate communication and echolocation is described. Development of auditory structures are described by five general levels of structural advancement. A review of acoustic communication systems for major animal groups is presented. The emergence of echolocation is described. For a discussion of cognitive aspects see Evans and Norris, 1988.

Northrop, J., W. C. Cummings, and P. O. Thompson. 1968. 20-Hz Signals Observed in the Central Pacific. Jour. Acoust. Soc. Am. 43 (2):383-384.

20-Hz signals recorded in the mid-Pacific area had source levels that ranged from 65 to 100 dB re 1 ubar at 1 yard. The original strength, source movement, and seasonal peak suggested the sounds were from a biological source, probably the finback whale.

Northrop, J., W. C. Cummings, and M. F. Morrison. 1971. Underwater 20-Hz Signals Recorded Near Midway Island. Jour. Acoust. Soc. Am. 49 (6, Pt. 2): 1909-1910.

This paper describes doublets of 25-second, 20-Hz signals believed to be from whales. Signals occurred in trains of source levels ranging from 53 to 71 dB re 1 ubar at 1 yard.

Pawloski, D. A., and P. W. B. Moore. 1987. Combined Stimulus Control of Peak Frequency and Source Level in the Echolocating Dolphin (Tursiops truncatus). 15th Annual IMATA Conf., New Orleans, LA, Oct. 26, 1987, pp. 3-9.

The training methods by which an echolocating dolphin was trained to control its emitted source level and the frequency content of the echolocation click are presented.

Penner, R. H., and A. E. Murchison. 1970. Experimentally Demonstrated Echolocation in the Amazon River Porpoise, Inia geoffrensis. NUC TP 187, 28 pp.

An analysis of the ability of a freshwater porpoise to discriminate, by echolocation, wires or tubes of different diameters.

Penner, R. H., and J. Kadane. 1980. Tursiops Biosonar Detection in Noise. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 957-959.

In a detection problem in a high ambient noise environment with presentation of white noise at five different levels, the overall performance of two Tursiops degraded as noise level increased. The click count ("echolocation effort") and response latency both increased until the noise exceeded 77 dB. At the two highest levels, 82 and 87 dB, the click trains became shorter and latencies were longer.

Penner, R. H., and J. Kadane. 1980. Biosonar Interpulse Interval as an Indicator of Attending Distance in Tursiops truncatus. (Abs.) Jour. Acoust. Soc. Am. 80 (Suppl. 1): S97.

In a biosonar detection study, the relationship between interpulse interval lengths and calculated acoustical two-way travel time was found to describe an attending distance appropriate to the distance between animal and target.

Penner, R. H., and C. W. Turl. 1983. Bottlenosed dolphin (Tursiops truncatus): Difference in the pattern of interpulse intervals. (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): S74.

When the echolocation detection abilities of a bottlenosed dolphin and a beluga were tested on identical targets at the same distances, their interpulse interval distributions differed, but detection accuracy was not significantly different.

Penner, R. H., C. W. Turl, and W. W. L. Au. 1986. Target Detection by the Beluga Using a Surface-Reflected Path. Jour. Acoust. Soc. Am. 80:1842-1843.

During an echolocation-in-noise experiment, a beluga was suspected of using a surface-reflected path to maximize detection performance. Tests confirmed this.

Penner, R. H. 1988. Attention and Detection in Dolphin Echolocation. In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 707-713.

The results of experiments examining the interpulse interval of echolocation pulses in the bottlenosed dolphin are presented. The effect of target distance on interpulse interval is discussed.

Powell, B. A. 1966. Periodicity of Vocal Activity of Captive Atlantic Bottlenosed Dolphins (Tursiops truncatus). Bull. So. Calif. Acad. Sci. 65 (4):237-244.

Periodicity of vocal activity was found to be related to feeding periods and could be altered by changing the feeding schedule.

Ridgway, S. H. 1980. Electrophysiological Experiments on Hearing in Odontocetes. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 484--493.

Review of findings on dolphin hearing, with accounts of modern anatomic and physiologic work on the ear; the brain, evoked potentials, and audition; and evidence that sound production can be used to assess dolphin health and mood.

Ridgway, S. H., D. A. Carder, R. F. Green, A. S. Gaunt, S. L.L. Gaunt, and W. E. Evans. 1980. Electromyographic and Pressure Events in the Nasolaryngeal System of Dolphins During Sound Production. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 239-249.

Study of the gross and microanatomical nature of the nasal plug nodes, diagonal membrane, and nasofrontal sacs, coupled with acoustic, electromyographic, and pressure measurements strongly indicated that this system constitutes the source of sound production. The data show no evidence for sound production in the larynx.

Ridgway, S. H. 1983. Dolphin Sound Production: Physiologic, Diurnal, and Behavioral Correlations. (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): S73.

Identifies unanswered questions regarding mechanics of dolphin sound production and states findings on correlations identified in the title.

Ridgway, S. H., and D. A. Carder. 1983. Audiograms for Large Cetaceans: A Proposed Method for Field Studies. (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): S53.

Audiograms for small cetaceans have been produced by the averaged-brainstem response technique using EEGs recorded when sound pulses are presented via a hydrophone. It is proposed that this technique could be used to obtain audiograms from large whales that have become trapped, stranded, or beached.

Ridgway, S. H., and D. A. Carder. 1988. Nasal Pressure and Sound Production in an Echolocating White Whale (Delphinapterus leucas). In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 53-60.

Nasal cavity pressures were measured while an echolocating beluga performed a discrimination task; the pressures increased whenever the whale emitted echolocation pulses or whistles. Open catheters distorted or prevented pulse and whistle production. The nasal apparatus is structured to tolerate high differential pressures produced during sound production; such pressure would be detrimental to critical thoracic circulation.

Ridgway, S. H., and D. A. Carder. 1990. Sounds Made by a Neonatal Sperm Whale, Physter spp. Jour. Acoust. Soc. Am. 88 (Suppl. 1): S6.

Broadband recordings were made from a baby sperm whale. The sounds of the whale were described according to type and location of production.

Ridgway, S. H., D.A. Carder and T.A. Romano 1991. The Victory Squeal of Dolphins and White Whales at the Surface and at 100m or More in Depth. Jour. Acoust. Soc. Am. 90:2335.

Investigates and analyzes the victory squeal, a recognizable rapid pulse train of dolphins and white whales after successfully completing auditory tasks.

Ridgway, S. H., D. A. Carder, P. L. Kamolnick, D. J. Skaar, and A. Root 1991. Acoustic Response Times (RTs) for Tursiops truncatus. Jour. Acoust. Soc. Am. 89:1967-1968.

Dolphins (Tursiops truncatus) were trained to make underwater acoustic responses (ARs = whistles or pulse trains) to tonal or click train stimuli (St). St delivery and AR and RT recordings were computer controlled. Response times (RTs) varied with the individual bottlenosed dolphin, and with amplitude and duration of St. Median RT typically was less than the mean by one to five percent. Median simple RT (1 St, 1 AR) ranged from 145 msec to just over 300 msec. Median choice RT (2 unlike random St, 2 unlike ARs) ranged from 170 to 448 msec.

Ridgway, S.H. and D.A. Carder. 1993. High-Frequency Hearing Loss in Old (25+ Years Old) Male Dolphins. Jour. Acoust. Soc. Am. 94 (3): 1830.

Old male dolphins tend to have high frequency hearing loss not typically found in young males and females or in old females.

Ridgway, S.H. and D.A. Carder. 1994. Auditory Evoked Potentials for Assessment of Hearing in Marine Mammals. Jour. Acoust. Soc. Am. 96: 3269.

The development of a method for collecting hearing data in non-trained animals including beached or entrapped large whales is described.

Ridgway, S.H. and D.A. Carder. 1995. Whale Physiology at Depth: Hearing, Sonar, and Homeostasis. 26th Annual Conf. of the International Association for Aquatic Animal Medicine. Mystic, CT, May 16-10, 1995, 26: 67.

A preliminary film report describing methods and approaches for studying hearing and physiology of trained whales in the open ocean.

Ridgway, S.H. and D.A. Carder. 1995. Deep Hearing and Sonar Studies of Conditioned White Whales, Delphinapterus leucas. 11th Biennial Conf. on the Biology of Marine Mammals, Orlando, FL, Dec. 14-18, p. 96.

Hearing testing of white whales diving as deep as 200 m was described and a film report was presented.

Ridgway, S.H. and D.A. Carder. 1996. Hearing Deficits Measured in Some Tursiops truncatus, and Discovery of a Deaf/Mute Dolphin. 26th Annual Conf. of the International Association for Aquatic Animal Medicine, Mystic, CT, May 16-10, 1995, 26: 41.

Eight dolphins were tested for hearing ability. Three males showed hearing disability at higher frequencies above about 60 kHz. An animal with behavioral indications of hearing deficit was tested and found to be deaf.

Ridgway, S.H. 1997. Who are the Whales? Bioacoustics. 8: 3-20.

Cetaceans are born in water and spend their entire lives in the aquatic medium. Small and large species occupy all oceans from the equator to the polar seas; some inhabit rivers; and four species live only in fresh water. There is a great gap in knowledge about hearing in most cetacean species and especially about how noise and high-intensity sound may affect all cetaceans and other mammals under water. Studies of temporary threshold shift (TTS) and occupational noise exposure in human divers suggest a cautious approach to cetacean noise exposure until data on cetacean TTS can give some idea of the dynamic range of their ears.

Ridgway, S.H. 1997. Toward a Scientific Basis for Understanding Noise Effects on

Marine Mammals. International Association for Aquatic Animal Medicine, Harderwijk, The Netherlands, May 3-8, p. 1-2.

This study determined the effect of depth on hearing of two white whales trained to dive down to 300 meters in the Pacific Ocean. Demonstrated capability for acoustic testing of whales in their natural environment, the open sea, and provided the first audiogram of any whale in the open sea.

Ridgway, S.H. and D.A. Carder. 1997. Hearing Deficits Measured in Some Tursiops

truncatus, and Discovery of a Deaf/Mute Dolphin. Jour. Acoust. Soc. Am. 101 (1): 590-594.

See Ridgway and Carder, 1996, above.

Ridgway, S.H., D.A. Carder, R. Smith, T. Kamolnick, and W. Elsberry. 1997. First Audiogram for Marine Mammals in the Open Ocean and at Depth: Hearing and Whistling by Two White Whales Down to 30 Atmospheres. Jour. Acoust. Soc. Am. 101: 3136.

To test the effect of depth on the hearing of an odontocete cetacean, two white whales were trained to dive and station on a platform at 5, 100, 200, or 300 m in the Pacific Ocean and whistle when they heard a 500 ms tone from a hydrophone. Findings after 885 dives support theories that sound is conducted through whale head tissues to the ear without the usual ear drum/ossicular chain amplification of the aerial middle ear. These first ever hearing tests in the open ocean demonstrate that whales hear as well at depth as near the surface; therefore, zones of influence for human-made sound are just as great throughout the depths to which whales dive, or at least to 300 m.

Roitblat, H. L., R. H. Penner, and P. E. Nachtigall. 1988. Delayed Matching-To-Sample by an Echolocating Bottlenosed Dolphin. (Abs.) Jour. Acoust. Soc. Am. 84 (Suppl. 1): S77.

A bottlenosed dolphin’s clicks were monitored in a three-alternative, delayed matching-to-sample experiment. Analysis showed a complex decision-making process combining stereotypic and contingent behavior to produce accurate performance.

Roitblat, H. L., R. L. Penner, and P. E. Nachtigall. 1989. Echolocation Matching-to-Sample: The Microstructure of Decision-making. (Abs.) Bulletin of the Psychonomic Society. 30th Annual Mtg. of the Psychonomic Society, Atlanta, GA., 27(6):495.

A bottlenosed dolphin was studied in a three-alternative matching-to-sample echolocation task. Distribution of effort during the task was related to stimulus characteristics to help define the dolphin’s decision-making process.

Roitblat, H. L., R. H. Penner, and P. E. Nachtigall. 1990. Attention and Decision-Making in Echolocation Matching-to-Sample by a Bottlenosed Dolphin (Tursiops truncatus): The Microstructure of Decision-Making. In: Sensory Abilities of Cetaceans, J. Thomas and R. Kastelein (eds.). Plenum Press, New York, pp. 665-676.

A discussion of the sequential sampling model and the problems of combining information from successive echoes. This paper also describes how the dolphin’s echo-location signal varied over successive clicks.

Roitblat, H. L., R. H. Penner, and P. E. Nachtigall. 1990. Matching-to-Sample by an Echolocating Dolphin. Jour. Exper. Pysch: Animal Behavior Processes. 16(1):85-95.

Describes a dolphin’s recognition performance and develops a sequential sampling model of dolphin choice performance in a delayed matching-to-sample task.

Roitblat, H. L., P. W. B. Moore, D. A. Helweg, and P. E. Nachtigall. 1991. Material Matching by a Bottlenosed Dolphin. (Abs.). Bulletin of the Psychonomic Society. 32nd Annual Mtg. of the Psychonomic Society, San Francisco, November 1991, 29(6):504.

Describes preliminary data concerning the dolphin’s ability to discriminate stimuli that varied only in internal material, but were identical in shape.

Roitblat, H. L., L. M. Herman, and P. E. Nachtigall. 1993. Language and Communication: Comparative Perspectives. Lawrence Erlbaum Associates, Hillsdale, NJ, 502 pp.

This book was the product of a conference on language and related cognitive processes in animals, which brought together scientists working on language and communication, to review the work done on language in apes and dolphins, and to place this work in a larger perspective of animal communication and cognition.

Roitblat, H.L., D.A. Helweg and H.E. Harley. 1995. Echolocation and Imagery. In: Sensory Systems of Aquatic Mammals, R.A. Kastelein, J.A. Thomas and P.E. Nachtigall (eds.), DeSpil Publishers, Woerden, The Netherlands, pp. 171-181

Discusses the concept of imagery—the suggestion that bats and dolphins form images of the objects they echolocate—and separates it from its visual connotations. Suggests this concept should be understood as an object-centered representation that preserves structural properties of the object rather than as a claim of vision-like representations.

Roitblat, H.L., D. Ketten, W.W.L. Au and P.E. Nachtigall. 1996. A Computational Model of Early Stages of Dolphin Hearing. (Abs.) Jour. Acoust. Soc. Am. 100 (4, Pt. 2): 2643.

A computational model of the early stages of dolphin hearing was developed to model dolphin echolocation performance. A three-stage process resulted in a stable auditory "image" or time-frequency map of a synthesized dolphin signal.

Schusterman, R. J., R. F. Balliet, and J. Nixon. 1972. Underwater Audiogram of the California Sea Lion by the Conditioned Vocalization Technique. Jour. Exper. Anal. Behavior 17:339-350.

Conditioned vocalizations were used to obtain underwater sound detection thresholds at ranges from 0.25 to 64 kHz. Maximum sensitivity was between 1 and 28 kHz. With relatively intense acoustic signals, Zalophus will respond to frequencies at least as high as 192 kHz.

Schusterman, R. J., B. Barrett, and P. W. B. Moore. 1975. Detection of Underwater Signals by a California Sea Lion and a Bottlenosed Porpoise: Variation in the Payoff Matrix. Jour. Acoust. Soc. Am. 57(6, Pt. 2): 1526-1532.

Results indicated that varying the payoff matrix (number of fish given for correct performance) may be an effective way to control response bias in experiments dealing with the detection of underwater signals by marine mammals.

Schusterman, R. J., and P. W. B. Moore. 1978. The Upper Limit of Underwater Auditory Frequency Discrimination in the California Sea Lion. Jour. Acoust. Soc. Am. 63(5): 1591-1595.

Frequency discrimination for pure tone and the associated Weber ratios for this species are presented and compared to other marine mammals previously measured. Frequency discrimination in pinnipeds is discussed.

Schusterman, R. J., and P. W. B. Moore. 1978. Underwater Audiogram of the Northern Fur Seal (Callorhinus ursinus) Jour. Acoust. Soc. Am. 64 (Suppl. 1A): S87.

The underwater audiogram of two Alaskan fur seals is presented.

Schusterman, R. J. 1980. Behavioral Methodology in Echolocation by Marine Mammals. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 11-41.

A comprehensive review of methodology and experimental design in echolocation studies of marine mammals.

Schusterman, R. J., D. A. Kersting, and W. W. L. Au. 1980. Response Bias and Attention in Discriminative Echolocation by Tursiops truncatus. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 983-986.

Describes an experiment testing the notion that a response bias acquired in an unsolvable discriminative echolocation task will strongly influence the attention of a dolphin in a similar but solvable task. The results indicated this occurred.

Schusterman, R. J., and P. W. B. Moore. 1980. Auditory Sensitivity of Northern Fur Seals (Callorhinus ursinus) and a California Sea Lion (Zalophus californianus) to Airborne Sound. (Abs.). Jour. Acoust. Soc. Am. 68 (Suppl. 1): S6.

At even frequencies, from 1 to 30 kHz, the thresholds, although inferior in air compared to water, showed good accommodation for hearing airborne sounds. The otariic pinnipeds appear to be more sensitive to airborne sounds than do the phocid pininipeds.

Schusterman, R. J., D. A. Kersting, and W. W. L. Au. 1980. Stimulus Control of Echolocation Pulses in Tursiops truncatus. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 981-982.

A major problem in determining what cue or set of cues a dolphin uses in target detection or discrimination has been the ambiguous nature of the echo return relative to the position of the dolphin. In this experiment the problem was solved by training the dolphin to position precisely and emit echolocation pulses on cue.

Schusterman, R. J., and P. W. B. Moore. 1981. Noise Disturbance and Audibility in Pinnipeds. Jour. Acoust. Soc. Am. 70 (Suppl. 1A): S83.

Noise and its disturbance impact on various species of wild pinnipeds are discussed.

Scronce, B. L., and C. S. Johnson. 1975. Bistatic Target Detection by a Bottlenosed Porpoise. Jour. Acoust. Soc. Am. 59(4):1001-1002.

The porpoise was acoustically masked to prevent use of its echolocation pulses and trained to report the presence or absence of a 7.62-cm-diameter hollow stainless steel sphere by listening. The sphere was ensonified by a broadband, click-type pulse.

Scronce, B. L., and S. H. Ridgway. 1980. Gray seal, Halichoerus: Echolocation Not Demonstrated. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 991-993.

A gray seal, trained to wear a blindfold, was tested for echolocation capability in detection and discrimination tasks. Successful detection of an air-filled ring occurred with and without head scanning and emission of click trains, suggesting that the ring was a good passive target. Performance in a discrimination task was at a chance level.

Scronce, B. L., and S. H. Ridgway. 1983. Seal Blindfolded Discrimination: Echolocation Not Proven in Halichoerus grypus. (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): S75.

Experiments with a gray seal trained to wear an opaque band that blocked vision provided no evidence of an echolocation capability.

Seeley, R. L., W. F. Flanigan, Jr., and S. H. Ridgway. 1976. A Technique for Rapidly Assessing the Hearing of the Bottlenosed Porpoise (Tursiops truncatus). NUC TP 522, 15pp.

Brainwave activity was used to determine approximate auditory "threshold" levels. This rapid (4-6 hour) technique provides an estimation of the hearing ability of an unanesthetized porpoise over a frequency range of 5 to 200 kHz and could be used to screen hearing in other marine mammals.

Sigurdson, J. E. 1987. Reproduction of Frequency-Modulated Tones by Dolphins (Tursiops truncatus) (Abs.). Seventh Biennial Conf. on the Biology of Marine Mammals, Society of Marine Mammalogy, Miami, FL., p. 64.

The ability of a bottlenosed dolphin to reproduce artificial, frequency-modulated whistles was evaluated. The animal was trained to produce highly accurate reproductions of each of three acoustic models in separate training sequences. The results demonstrate the flexibility of the animal’s sound-producing mechanism as well as the feasibility of preprogrammed training and evaluation of acoustic responses.

Sigurdson, J. E. 1989. Frequency-Modulated Whistles as a Medium for Communication with the Bottlenose Dolphin (Tursiops truncatus). (Abs.) Animal Language Workshop, Honolulu, HI, April 1989.

Review of procedures and early findings on the use of operant contingencies to condition FM CW whistles.

Sigurdson, J. E. 1991. Echolocation Pulse-Rate and Head-Azimuth of an Atlantic Bottlenose Dolphin in a Detection Task. (Abs.) Jour. Acoust. Soc. Am. 90 (4, Pt. 2): 2334.

Report of procedures and initial findings for biosonar search and detection of water-column objects in an open field. Baseline performance descriptions as well as pulse-count and echo-pulse interval as functions of object distance.

Sigurdson, J. E. 1991. Reproduction of Arbitrary Frequency-Modulated Tones and Object Labeling by Dolphins (Tursiops truncatus). (Abs.) Ninth Biennial Conf. on the Biology of Marine Mammals, Chicago, IL, Dec. 1991.

Reports the successful four-alternative, conditional discrimination of four objects using four conditioned, arbitrary, FM CW acoustic responses that were evaluated in real-time with automated signal recognition.

Sigurdson, J. E. 1993. Frequency-Modulated Whistles as a Medium for Communication with the Bottlenose Dolphin (Tursiops truncatus). In: Language and Communication: Comparative Perspectives, H.L. Roitblat, L.M. Herman and P.E. Nachtigall (eds.). Lawrence Erlbaum Associates, Erlbaum, NJ, pp. 153-173.

Research review with current methods and results of conditioning FM CW signals with operant contingencies to match arbitrary acoustic models. Controlled training and testing demonstrate that operant contingencies alone are not sufficient to induce model-copying behavior or "acoustic mimicry." Probable causes are discussed.

Sigurdson, J. E. 1994. Dynamics of Biosonar Echolocation in the Dolphin. (Abs.) Critical Issues in Replicating Biosonar Conference, San Diego, CA, Dec. 1994.

Reviewed work on biosonar dynamics with proposals for future research.

Sigurdson, J. E. 1994. Dynamics of Dolphin Biosonar Search and Detection. (Abs.) Jour Acoust. Soc. Am. 96 (5, Pt. 2): 3316.

Results of 2-D search and detection of water-column objects in an open field from an enclosed pen. Extensions for open-ocean research were described.

Sigurdson, J. E. 1996. Open-Water Echolocation of Bottom Objects by Dolphins (Tursiops truncatus). (Abs.) Jour. Acoust. Soc. Am. 100 (4, Pt. 2): 2610.

The attitude, azimuth, pulse-rate and waveform were recorded during open-water search for bottom objects. Results include baseline dynamic performance, search-pattern adaptation to experience, head attitude/azimuth and pulse-rate correlations with object location and inverse variation of pulse-count with object-distance. Spectral modulation as a function of background and novelty was analysed.

Sigurdson, J. E. 1997. Adaptations of Dolphin Biosonar to the SW/VSW Environment. (Abs.) Abstracts of the Environmentally Adaptive Sonar Technology (EAST) Symposium. Seattle, WA, Jan. 1997.

Described the major physiological adaptations of dolphin biosonar to shallow and very shallow water and the effects of experience on the dynamic use of that sonar in open-water search and detection tasks.

Sigurdson, J. E. 1997. Analyzing the Dynamics of Dolphin Biosonar During Search and Detection Tasks. Invited paper. Symposium on Underwater Bio-Sonar and Bioacoustics, British Institute of Acoustics, Loughborough University, Vol. 19, No. 9, pp. 123-132.

Describes technology for measurement of head movements and acoustic output of the bottlenose dolphin as well as methods for testing and analysis of the animal's dynamic biosonar performance. Data presented on biosonar performance during search for and detection of water-column objects in an open field and bottom objects in the open ocean.

Sigurdson, J. E. 1997. Biosonar Dynamics of the Bottlenose Dolphin in VSW Search and Detection Tasks. (Abs.) Jour. Acoust. Soc. Am. 105 (5, Pt. 2): 3133.

Describes intial analysis of the dolphin's dynamic biosonar performance during search for and detection of bottom objects in the open ocean. Findings included quantitative descriptions of typical 3-D search patterns, shorter than expected echo-pulse intervals and spectral variation between pulses that appeared to correlate with grazing angle and distance.

Thomas, J.A. 1987. Factors That May Affect Sound Propogation from Acoustic Harassment Devices. Proceedings, Acoustical Deterrents in Marine Mammal Conflicts with Fisheries Workshop, B.R. Mate and J.T. Harvey (eds.) Newport, OR, Febr. 17-18, 1986. Oregon State University Publication No. ORESUW-86-001.

The oceanographic conditions that could affect the use of acoustic devices to control movements of marine mammals around fishing grounds are described. Some species of specific concerns are given. In addition, some practical and logistical considerations are described relative to the use of sounds to deter marine mammals around human activities.

Thomas, J. A., R. A. Puddicombe, M. George, and D. Lewis. 1988. Variations in Underwater Vocalizations of Weddell Seals (Leptonychotes weddelli) at the Vestfold Hills as a Measure of Breeding Population Discreetness. Hydrobiologia 165:279-284.

Common characteristics of vocalizations were compared to assess the degree of mixing among populations from three areas. Results indicate one population was distinct.

Thomas, J. A., M. Stoermer, C. Bowers, L. Anderson, and A. Garver. 1988. Detection Abilities and Signal Characteristics of Echolocating False Killer Whales (Pseudorca crassidens). In: Animal Sonar Processes and Performance, P. E. Nachtigall and P. W. B. Moore (eds.). Plenum Press, New York, pp. 323-328.

Preliminary studies of echolocation abilities were conducted on false killer whales housed at Sea World San Diego and Sea Life Park in Hawaii. This study showed this species could detect a metal sphere at short ranges when not visible by using echolocation. Some low-frequency and high-frequency components were present in the echolocation clicks.

Thomas, J. A., N. K. W. Chun, W. W. L. Au, and K. Pugh. 1988. Underwater Audiogram of a False Killer Whale (Pseudorca crassidens). Jour. Acoust. Soc. Am. 84 (3): 936-940.

The behavioral audiogram showed maximum sensitivities between 16 and 64 kHz and was similar to beluga whale and bottlenosed dolphin sensitivities. Sensitivity decreased rapidly above 64 kHz.

Thomas, J. A., W. W. L. Au, C. W. Turl, and J. L. Pawloski. 1989. Sensory Systems of False Killer Whales. (Abs.) Eighth Biennial Conf. on the Biology of Marine Mammals, Society of Marine Mammalogy, Pacific Grove, CA., p. 67.

Studies on hearing and echolocation abilities are summarized. Results compared with bottlenosed dolphin and beluga studies.

Thomas, J. A., and C. W. Turl. 1990. Echolocation Characteristics and Range Detection Threshold of a False Killer Whale (Pseudorca crassidens). In: Sensory Abilities of Cetaceans, J. A. Thomas and R.A. Kastelein (eds.). Plenum Press, New York, pp. 321-334.

The range-detection abilities for a false killer whale was tested on Skyhook II range in Kaneohe Bay, Hawaii. The target was a 7.6-cm-diameter hollow metal sphere. The maximum detection range (50-percent correct detections) was measured at 115 meters. These values are comparable to belugas and bottlenosed dolphins tested on the same range.

Thomas, J. A., J. L. Pawloski, and W. W. L. Au. 1990. Masked Hearing Abilities in a False Killer Whale (Pseudorca crassidens). In: Sensory Abilities of Cetaceans, J. A. Thomas and R. A. Kastelein (eds.). Plenum Press, New York, pp. 395-404.

A masked hearing study was conducted on a female false killer whale using white noise as a masker. The response paradigm was a go/no-go and the signal was presented in staircase method. Three noise levels were used.

Thomas, J.A., P.W.B. Moore, P.E. Nachtigall, and W.G. Gilmartin. 1990. A New Sound From a Stranded Pygmy Sperm Whale. Aquatic Mammals. 16 (1): 28-30.

A pygmy sperm whale beached on the northeast shore of Oahu, Hawaii and was held temporarily at Sea Life Park. Underwater recordings were made using broadband equipment. On several occasions the animal produced a low-frequency, low-amplitude sound, but no echolocation-like clicks.

Thomas, J. A., P. W. B. Moore, R. Withrow, and M. Stoermer. 1990. Underwater Audiogram of a Hawaiian Monk Seal (Monachus schauinslandi). Jour. Acoust. Soc. Am. 87 (1): 417-420.

An underwater hearing test was conducted on a young male Hawaiian monk seal at Sea Life Park, Oahu, Hawaii. The response paradigm was go/no-go and signals were presented from 2 to 48 kHz using a staircase presentation. Maximum hearing sensitivity (20 dB from maximum sensitivity) was between 12 and 28 kHz.

Thompson, P. O. 1965. Deep-Water Recordings of Pinniped Sounds. Addendum to Proceedings, Second Conf. on Biological Sonar and Diving Mammals, Menlo Park, CA, 11pp.

Describes, in detail, underwater recordings of barking sounds from California sea lions off San Clemente Island. Diurnal characteristics, spectrum plots, and sonograms are included.

Thompson, P. O., and W. C. Cummings. 1969. Sound Production of the Finback Whale (Balaenoptera physalus) and Eden’s whale (B. edeni) in the Gulf of California. (Abs.) Sixth Conf. on Biological Sonar and Diving Mammals, Menlo Park, CA, p. 109.

Describes powerful, low-frequency sounds from two species of whales found in the Gulf of California. Finback signals ranged from 20 to 100 Hz, while those from Eden’s whales averaged 124 Hz. Although finbacks have been suspected as sources of 20-Hz signals, these were not encountered among the 1800 phonations recorded from some 70 finbacks.

Thompson, P. O. 1978. Underwater Repetitive Mammal Sound Sequences in the Bering Strait. (Abs.) Jour. Acoust. Soc. Am. 64 (Suppl. 1): S87.

Sounds similar to, but simpler than, the "songs" of the humpback whales were recorded. Among possible sources were the walrus and the bowhead whale.

Thompson, P. O., and W. A. Friedl. 1982. A Long-Term Study of Low-Frequency Sounds from Several Species of Whales off Oahu, Hawaii. Cetology, No. 45, 19 pp.

Two bottom-mounted hydrophones were monitored from December 1978 through April 1981. Sounds of five whale species (humpback, fin, blue, sperm, and pilot) were identified. The "boing" sound was also recorded. Sounds were received most frequently in winter and spring, least frequently in July and October.

Turl, C. W., and R. H. Penner. 1983. Target Detection: Beluga Whale and Bottlenosed Dolphin Echolocation Abilities Compared. (Abs.) Jour. Acoust. Soc. Am. 74 (Suppl. 1): S74.

No significant difference in performance was found for five targets of the same size and target strength at distances of 40 to 120 m.

Turl, C. W. 1987. The Ability of the California Sea Lion (Zalophus californianus) to Bistatically Detect and Localize Echoes from Underwater Targets. Jour. Acoust. Soc. Am. 82(1):381-383.

A sea lion was required to detect and orient to echoes in noise. The sea lion’s performance decreased as S/N ratio decreased.

Turl, C. W., R. H. Penner, and W. W. L. Au. 1987. Comparison of Target Detection Capabilities of the Beluga and Bottlenosed Dolphin. Jour. Acoust. Soc. Am. 82 (5): 1487-1491.

The echolocation capabilities of a beluga (Delphinapterus leucas) and an Atlantic bottlenosed dolphin (Tursiops truncatus) were directly compared in a target detection experiment. Both animals were trained to detect targets in the presence of masking noise. Target detection performance was determined as a function of masking noise level at each target distance. The echo-to-noise ratio for the beluga at the 75-percent correct response threshold was approximately 1.0 dB compared to about 10 dB for the dolphin.

Turl, C. W., R. H. Penner, and W. W. L. Au. 1988. Masked Detection Thresholds for the Beluga and Bottlenosed Dolphin. In: Port and Ocean Engineering Under Arctic Conditions, Vol. II, , W. M. Sackinger, M. O. Jeffries, J. L. Imm and S. D. Treacy (eds.). Symposium on Noise and Marine Mammals. Geophysical Institute, University of Alaska, pp. 89-93.

A beluga and a bottlenosed dolphin detected spherical targets in noise at three distances. The beluga’s echo-to-noise ratio was approximately 10 dB better than the dolphin’s for all target ranges.

Turl, C. W., and R. H. Penner. 1989. Differences in Echolocation Click Patterns of the Beluga (Delphinapterus leucas) and the Bottlenosed Dolphin (Tursiops truncatus). Jour. Acoust. Soc. Am. 86 (2):497-502.

In an echolocation experiment, the target detection of a beluga and a bottlenosed dolphin were similar, but each produced different patterns of echolocation click trains. The beluga emitted click trains that were composed of "packets of clicks." The interpacket interval is longer than the total packet duration and greater than the two way travel time from the animal to the target. This suggests that the beluga can process all echoes of a packet before the next packet returns to the animal. The bottlenosed dolphin always emitted single clicks that are greater than the two-way travel time to the target.

Turl, C. W. 1991. Echolocation Abilities of the Beluga (Delphinapterus leucas): A Review and Comparison with the Bottlenosed Dolphin (Tursiops truncatus). In: Advances in Research on the Beluga Whales (Delphinapterus leucas), T. G. Smith, D. J. St. Aubin, and J. R. Geraci (eds.). Canadian Bulletin of Fisheries and Aquatic Sciences 224:119-128.

A review. The beluga’s bioacoustic abilities are not fully known, but information suggests its echolocation system is particularly well-suited to function in the Arctic environment.

Turl, C. W., D. J. Skaar, and W. W. L. Au. 1991. The Echolocation Ability of the Beluga (Delphinapterus leucas) to Detect Targets in Clutter. Jour. Acoust. Soc. Am. 89 (2): 896-901.

A beluga was trained to detect different length cylinders in front of a clutter screen at five separation distances. Detection data were collected on the beluga’s performance as function of the separation between the targets and clutter screen. The beluga’s performance was above 80 percent correct detection for the 14- and 10-cm cylinders as the separation distance decreased from 10.1 to 5.1 cm. For all targets except the 3-cm cylinder, the beluga’s performance was higher at 0-cm separation than at 2. 5-cm separation. The results indicate that a beluga can detect targets in 3.6 to 5.4 dB more reverberation than previously reported for a bottlenosed dolphin.

Turl, C.W. and J.A. Thomas. 1992. Possible Relationship Between Oceanographic Conditions and Long Range Target Detection by a False Killer Whale. In: Marine Mammal Sensory Systems, J.A. Thomas, R.A. Kastelein and A.Y. Supin (eds.). Plenum Press, New York.

Reports on study to determine whether sound velocity profiles in water of an echolocating false killer whale (Pseudorca crassidens) changes detection range. The whale's detection performance decreased as distance to the target increased.

Wenz, G. M. 1964. Curious Noises and the Sonic Environment in the Ocean. In: Marine Bio-Acoustics, Vol. 1, W. N. Tavolga (ed.). Pergamon Press, Elmsford, NY, pp. 101-119.

Describes ambient noise of the ocean - waves, precipitation, earthquakes, ships, marine organisms, etc., and discusses certain noises of biological origin, including some whose sources had not been identified.

Wever, E. G., J. G. McCormick, J. Palin, and S. H. Ridgway. 1972. Cochlear Structure in the Dolphin (Langenorhynchus obliquidens). Proc. Nat. Acad. Sci. USA 69 (3): 657-661.

Describes the microscopic structure of the cochlea and discusses the significance of cell numbers in the hearing of Langenorhynchus.

Wood, F. G., and W. E. Evans. 1980. Adaptiveness and Ecology of Echolocation in Toothed Whales. In: Animal Sonar Systems, R. G. Busnel and J. F. Fish (eds.). Plenum Press, New York, pp. 381-425.

Review of echolocation signal characteristics of various toothed whales with respect to their different ecological niches, foods, behaviors, etc. It is proposed that certain asymmetrical features (skull, narial system) are related to the development of a sonar system. Differences in relative brain size appear to correspond to degree of adapatibility, sensory integration, and versatility of sonar system.

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