SOUND/SONAR/COMMUNICATION

Altes, R. A., W. E. Evans, 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. pp. 853-854, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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. 1988. Instrumentation for Dolphin Echolocation Experiments. (Abstract) Jour. Acoust. Soc. Am. vol. 83, suppl. 1, p. 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, pp. 451-465, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

Reviews sonar detection and discrimination experiments conducted in open waters of Kaneohe Bay, Hawaii with Bottlenose 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, pp. 753-768, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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.

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

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 L. L. Jones. 1989. Target Strength Measurements of Nets and Implications Concerning Incidental Take of Dall's Porpoises. (Abstract) Abstracts of the Eighth Biennial Conf. on the Biol. of Mar. Mammals, Soc. Mar. Mammalogy, 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 stili occurs were suggested.

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

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 dis- crimination, 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 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.

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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(S1)A, S-107.

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 microseconds.

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, pp. 295-299, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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

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

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 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., and D. A. Pawloski. 1990. Cylinder Wall Thickness Difference Discrimination by an Echolocating Dolphin. Jour. Acoust. Soc. Am. suppl. 1 88:S4.

Discusses an experiment in which 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

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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 J. L. Pawloski. 1988. The Perception of Time-Separation Pitch by Dolphins. (Abstract) Jour. Acoust. Soc. Am., vol 83, suppl. 1, p. 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 deter- mined. 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 ta 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 CLS. 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 C. T. 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 angle. 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., 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

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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., 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-ti68.

"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 microseconds.

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

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

A review, with additional previously unpublished data.

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). (Abstract) Jour. Acoust. Soc. Am. vol. 64, suppl. 1, p. 587.

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.

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

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, pp. 859-862, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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.

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Au, W. W. L., R. H. Penner, and J. Kadane. 1982. Acoustic Behavior of Echolocating Atlantic Bottlenosed 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). (Abstract) Jour. Acoust. Soc. Am. vol. 70, suppl. 1, p. 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 . vol. 72, suppl. 1, p. 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. (Abstract) Jour. Acoust. Soc. Am. vol. 74, suppl. 1, pS73.

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 161z. 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

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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., P. W. S. 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.

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 Environ- mental Information between Bottlenosed Dolphins. In: Animal Sonar Systems--Biology and Bionics, vol. II, pp. 803-873, ed. R. G. Busnel, Laboratoire de Physiologie Acoustique, Jouy-en-Josas 78, France.

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) (Abstract). Abstracts of the Eighth Biennial Conf. on the Biol. of Mar. Mammals, Soc. Mar. Mammalogy, Pacific Grove, CA., p. 8.

See Brill and Harder, 1991, of this section.

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Brill, R. L., and P. J. Harder. 2991. 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.

Bullock, T. H., S. H. Ridgway, and N. Sa??ga. 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, pp. 373-395, ed. S. R. Galler et al., NASA Pub SP-262.

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 mod- est 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. 1990. Auditory Brainstem Response in a Neonatal Sperm Whale, Physeter spp. Jour. Acoust. Soc. Am ., suppl. 1, 88: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

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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. A., and S. H. Ridgway. 1983. Apparent Echolocation by a Sixty-day-old Bottlenosed Dolphin, Tursiops truncatus. (Abstract) Jour. Acoust. Sac. Am. vol. 74, suppl. 1, p. S74.

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

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. (Abstract) Jour. Acoust. Soc. Am. vol. 73, suppl. 1, p. 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). (Abstract) Jour. of Acoust. Soc. Am. 44(5):1211.

Abstract of a paper presented to the ASA 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 yd. 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.

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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 microbar) 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: RN 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.

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.

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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):172-1732.

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.

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

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 Sanar Systems - Biology and Bionics, vol. 1, p. 495-503, ed. R. G. Busnel, Laboratoire de Physiologie Acoustique, Jouy-en-Josas 78, France.

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, pp. 366-383, ed. R. G. Busnel, Laboratoire de Physiologie Acoustique, Jouy-en- Josas 78, France.

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 ecological factors. In: The Biology of Marine Mammals, pp. 425-475, ed. H. T. Andersen, Academic Press, San Diego, CA.

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.

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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.

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, 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, pp.671-6&1, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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 hierarchies and cognitive aspects of language and echolocation are also reviewed.

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

Summarizes important contributions to our 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. Fisheries Bulletin 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.

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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 dis- crimination 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, pp. 615-623, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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 Per3'ormance, pp. 773-783, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York,

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

Friedl, W. A., and P. O. Thompson. 1981. Measuring Acoustic Noise Around Kahoolawe Island. NOSC TR 732, 15 pp. (Also, abstract in Jour. Acoust. Soc. Am. vol. 70, suppl. 1, p. S84, 1981).

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.

Gales, R. S. 1966. Pickup, Analysis, and Interpretation of Underwater Acoustic Data. In: Whales, Dolphins, and Porpoises, ed. K. S. Norris, 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. (Abstract) Jour. Acoust. Soc. Am., vol. 82, suppl. 1, p. S98.

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

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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, pp. 199-238, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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.

Hall, J. D., and C. S. Johnson. 1972. Auditory Thresholds of a Killer Whale (Orcinus orca). Linnaeus. Jour. Acoust. Sac. 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). (Abstract) Jour. Acoust. Soc. Am. vol. 64, suppl. 1, p. S8.7.

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.

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.

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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, 384-398, ed. R. G. Busnel, Laboratoire de Physiologie Acoustique Jouy-en-Josas 78, France.

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 Bio- Acoustics vol. 2, pp. 247-260, ed. W. N. Tavolga, Pergamon Press, Elmsford, NY.

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. 1970. Auditory Masking of One Pure Tone by Another in the Bottlenosed Porpoise. Jour. Acoust. Soc. Am. 48(5):7328.

Pure-tone masking-tone thresholds were obtained for a bottlenosed porpoise. Using a masking-tone frequency of 70 161z 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, pp. 515-518, eds, R. G. Busnel and J. F. Fish, Plenum Press, New York.

Discusses three apparent anomalies in experimental results on cetacean hearing.

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

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, pp. 769-771, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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

Johnson, C. S. 1991. Hearing Thresholds for Periodic 60-Hz Tone Pulses in the Beluga Whale. Jour. Acoust. Soc. Am. 89((I):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, 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, R. A. 1980. Energy Spectrum Analysis in Echolocation. In: Animal Sonar Systems, pp. 673-693, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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, pp.317-322, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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 sup- ports the hypothesis that the analysis of rippled spectra may be an important function of dolphin audition.

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Kadane, J., R. H. Penner, W. W. L. Au, and R. W. Floyd. 1980. Microprocessors in Collection and Analysis of Tursiops truncatus Echolocation Data. (Abstract) Jour. Acoust. Soc. Am. vol. 68, suppl. 1, p. 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.

Lang, T. G., and H. A. P. Smith. 1965. Communication Between Dolphins in Separate Tanks by Way of an Acoustic Link. Science 150(3705):1839-1843.

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

Ljungblad, D. K., and J. S. Leatherwood. 1979. Sounds Recorded in the Presence of Adult and Calf Bowhead Whales (Balaena mysticetus). NOSC TR 420, Revision 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. Mast sounds at both times were low-frequency (below 800 Hz) moans, simple or complex.

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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 19si).

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, pp. 567-579, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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. (Abstract) Jour. Acoust Soc. Am. vol. 68, suppl. 1, p. 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. (Abstract) Jour. Acoust. Soc. Am. vol. 73, suppl. 1, p. 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, pp. 829-833, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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

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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. Sac. 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, pp. 449-467, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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 are 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 com- pared 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. Sac. Am., 64(S1)A, 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.

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Moore, P.W.B. 19&0. Cetacean Obstacle Avoidance. In: Animal Sonar Systems, pp. 97-108, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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. (Abstract) Jour. Acoust. Soc. Am. vol. 70, suppl. 1, p. 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. (Abstract) Jour. Acoust. Soc. Am. vol. 70, suppl. `1, p. 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). Proceedings of the Fifth Annual Conf: on the Biol. of Mar. Mammals, Boston, MA, 70(4).

Moore, P. W. B., and W. W. L. Au. 1983. Critical Ratio and bandwidth of the Atlantic Bottlenosed Dolphin (Tursiops truncatus). (Abstract) Jour. Acoust. Soc. Am. vol. 74, suppl. 1, p. 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 microseconds. The animal's detection performance, high at long delays, dropped to chance level for a 100-microsecond 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.

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

Discusses experiments with a bottlenosed dolphin previously trained to shift its out- going emitted source level was 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, pp. 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, pp.161-168, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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. 1991. Dolphin Psychophysics: Concepts for the Study of Dolphin Echolocation. In: Dolphin Societies: Methods alf Study, eds. K. Pryor and K. Norris, University of California 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. 1989. Investigations on the Control of Echolocation Pulses in the Dolphin. Presented to the 5th International Theriological Congress, Rome Italy, 22-29 August, 1989

See Moore and Pawloski. 1990.

Moore, P. W. B., and D. A. Pawloski. 1990. Investigations on the Control of Echolocation Pulses in the Dolphin. In: Dolphin Sensory Processes, eds, Thomas, J.A. and R. Kas- telein, 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 dis- cussed. Results from several experiments are presented.

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Moore, P. W. B., H. L. Roitblat, P. E. Nachtigall, and R. H. Penner. 1990. Classifying Dolphin Echoes Using an Integrator Gateway Artificial Neural Network. Jour. Acoust. Soc. Am. 90(2):2334.

See other articles by Moore, et a1.,`1990.

Moore, P. W. B., H. L. Roitblat, R. H. Penner, and P. E. Nachtigall. 1990. An Integrator Gateway Network for Recognizing Dolphin Echoes. Government Neural Network Applications Workshop, August 29-31, 1990, San Diego CA.

The application of the gateway integrator neural network for classifying various signals was presented in this classified workshop.

Moore, P. W. B., H. L. Roitblat, R. H. Penner, and P. H. Nachtigall. 2990. An Integrator Gateway Network for Recognizing Dolphin Echoes. Neural Networks for Decision, Estimation, and Control, West Greenwich, Rhode Island.

A new neural network design based on the properties of the echolocating dolphin was presented and discussed in a classified conference on Government signal- processing approaches.

Moore, P. W. B., H. L. Roitblat, P. E. Nachtigall, R. H. Penner, and W. W. L. Au. 1990. Sonar Target Recognition by an Artificial Neural Network. Naval Research and Development Information Exchange Conference, NADC, Warminster, P.A., p 48.

Detailed presentation of the integrator gateway network. This network (patent applied for) combines information from multiple signals and resets between trains of signals. This artificial neural network model was compared against a standard neural network model that did not include the integrating components and was found to improve object recognition substantially.

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 indicate 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.

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

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.

Murchison, A. E., and S. A. Patterson. 1980. The Effect of Extended Reinforcement Schedules on the Receiver Operating Characteristics (ROC) of an Echolocating Atlantic Bottlenosed Dolphin (Tursiops truncatus). (Abstract) Jour. Acoust. Soc. Am. vol. 68, suppl. 1, p. 597.

After a dolphin was conditioned to report (by paddle press) presence or absence of a target, its performance was tested using different variable and fixed-ratio reinforcement schedules. The dolphin's ROC remained essentially unchanged for all schedules, but when it was kept on the more extended schedules for more than eight consecutive 100-trial sessions, all responses became "target absent."

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

A review.

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

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). (Abstract) Jour. Acoust Soc. Am. vol. 68, suppl. 1, p. 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.

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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, pp. 945-947, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York. (Also, abstract in Jour. Acoust. Soc. Am. vol. 64, suppl. 1, p. S87-1978).

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., 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 10-19 September 1986 in Helsignor, Denmark. This was the third international meeting on biosonar and contributors presented their most recent works.

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

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, pp. 655-669, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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 microbar at 1 yd. The original strength, source movement, and seasonal peak suggested the sounds were from a biological source, probably the finback whale.

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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-sec, 20-Hz signals believed to be from whales. Signals occurred in trains of source levels ranging from 53 to 71 dB re 1 microbar at 1 yd.

Pawloski, D. A., and P. W. B. Moore. 1987. Combined Stimulus Control of Peak Frequency and Source Level in the Echolocating Dolphin (Tursiops truncatus). In: Proceedings of the I5th International Marine Animal Trainers Association, New Orleans, Oct. 26, 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 is 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, pp. 957-959, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York .

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. (Abstract) Jour. Acoust. Soc. Am. vol. 80, suppl. 1, p. 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. (Abstract) Jour. Acoust. Soc. Am. vol. 74, suppl. 1, p. 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.

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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, pp. 707-713, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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., D. A. Carder, R. F. Green, A. S. Gaunt, S. L. L. Gaunt, and W. E. Evans. 19XO. Electromyographic and pressure events in the nasolaryngeal system of dolphins during sound production. In: Animal Sonar Systems, pp. 239-249, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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. 1980. Electrophysiological Experiments on Hearing in Odontocetes. In: Animal Sonar Systems, pp. 483-493, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

Review of findings on dolphin hearing, with accounts of modem 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., and D. A. Carder. 1983. Audiograms for Large Cetaceans: A Proposed Method for Field Studies. (Abstract) Jour. Acoust. Soc. Am. vol. 74, suppl. 1, p. 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 ta obtain audiograms from large whales that have become trapped, stranded, or beached.

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Ridgway, S. H. 1983. Dolphin Sound Production: Physiologic, Diurnal, and Behavioral Correlations. (Abstract) Jour. Acoust. Sac. Am. vol. 74, suppl. 1, p. 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. 1988. Nasal Pressure and Sound Production in an Echolocating White Whale (Delphinapterus leucas). In: Animal Sonar Processes and Performance, pp. 53-60, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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, Physeter spp. Jour. Acoust. Soc. Am. vol 88, suppl. 1, p. 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, 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 II 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. 1991. The Victory Squeal of Dolphins and White Whales at the Surface and at 100m or More in Depth. Jour. Acoust. Soc. Am. 90:233.

After seizing a fish, small odontocetes often emit a series of rapid clicks that we have come to call "victory squeal." When the animal is trained using a reinforcement stimulus (Sr), the "victory squeal" (Vs) was given after the Sr. Acoustic properties and latencies of the Vs are given along with a comparison of the Vs given at depth and at the surface. At depth, white whale Vs peak frequency is lower (Avg. 14.2 128

Roitblat, H. L., P. W. B. Moore, R. H. Penner, and P. E. Nachtigall. 1989. Clicks, Echoes, and Decisions: The Use of Information by a Bottlenosed Dolphin (Tursiops truncatus). (Abstract) Abstracts of the Eighth Biennial Conference on the Biology of Marine Mammals, Soc. Mar. Mammalogy, Pacific Grove, CA., p. 56.

Described the pattern by which the dolphin searched alternative comparison stimuli in a delayed matching-to-sample task and some preliminary neural network models for dolphin echolocation.

Roitblat, H.L., P. W. B. Moore, P. E. Nachtigall, R. H. Penner, and W. W. L. Au. 1989. Natural Echolocation With an Artificial Neural Network. International Journal of Neural Networks: Research and Applications, 1(4), pp. 239-248.

The performance of a dolphin performing in a matching-to-sample echolocation task was simulated with a counterpropagation artificial neural network. The neural net- work performance compared well with that of the dolphin when echoes collected while the dolphin echolocated were used.

Roitblat, H. L., P. W. B. Moore, P. E. Nachtigall, R. H. Penner, and W. W. L. Au. 1989. Dolphin Echolocation: Identification of Returning Echoes Using a Counterpropagation Network. Proc. Int. Joint Conf. on Neural Networks, vol. I IEEE and Int. Neural Network Soc., Piscataway, New Jersey, pp. 295-301.

Describes preliminary work on using a counterpropagation artificial neural network to recognize echoes from objects ensonified in a test pool by an artificial dolphin click and in Kaneohe Bay by a dolphin during performance of a delayed matching- to-sample task. Selected echoes were analyzed and successfully recognized by the network. Target recognition abilities of an echolocating dolphin and the neural network were also compared. In a noisy natural environment, the dolphin was 94.5 percent correct and the network was 96.7 percent correct. Possible applications of neural networks to echolocation studies are discussed.

Roitblat, H. L., R. L. Penner, and P. E. Nachtigall. 1989. Echolocation Matching-to- Sample: The Microstructure of Decision-making. Bulletin of the Psychonomic Society. Abstracts of the 30th Annual Meeting 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.

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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. pp. 665-676, eds. J. Thomas and R. Kastelein, Plenum Press, New York.

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

Roitblat, H. L., R. H. Penner, and P. E. Nachtigall. 1990. Matching-to-sample by an Echolocating Dolphin. In: Animal Behavior Processes, Journal of Experimental Psychology, 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. Bulletin of the Psychonomic Society, Abstracts of the 32nd Annual Meeting ofthe 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., P. W. B. Moore, P. E. Nachtigall, and R. H. Penner. 1991. Natural Dolphin Echo Recognition Using an Integrator Gateway Network. In Advances in Neural Information Processing Systems 3., pp. 273-281), eds. D. S. Touretsky, J. E. Moody and R. Lippman, Morgan Kaufmann, San Mateo, CA.

Discusses the integrator gateway network for recognizing objects ensonified by dolphin echolocation signals.

Roitblat, H. L., P. W. B. Moore, P. E. Nachtigall, and R. H. Penner. 1991. Biomimetic Sonar Processing: From Dolphin Echolocation to Artificial Neural Networks. In From Animals to Animats. pp. 66-76, eds. J. A. Meyer and S. Wilson, MIT Press, Cambridge, MA.

Describes a dolphin's recognition performance and some aspects of a neural net- work model of echo recognition that incorporated properties of the sequential sampling model to combine information from successive dolphin echoes.

Root, W. A., and S. H. Ridgway. 1991. Neural Network Applications in Dolphin Response-time Studies. Jour. Acoust. Soc. Am. 90: 2334.

Dolphins (Tursiops truncatus) were trained to make different sounds in response to two different acoustic stimuli produced by a computer system. A neural network was

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shown to be better at identifying response type and setting response latency than was a previously employed discriminant analysis routine.

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, Zalophlks will respond to frequen- cies 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):1526-2532.

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(S1)A, 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, pp. 11-41, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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, pp. 983-986, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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 that this happened.

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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. (Abstract) Jour. Acoust. Soc. Am. vol. 68, suppl. 1, p. S6.

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

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

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 an cue.

Schusterman, R. J., and P. W. B. Moore. 1981. Noise Disturbance and Audibility in Pinnipeds. Jour. Acoust. Soc. Am., 70(S1)A, p. 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-diam. 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, pp. 991-993, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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. (Abstract) Jour. Acoust. Soc. Am. vol. 74, suppl. 1, p. S75.

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

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Sigurdson, J. E. 1987. Reproduction of Frequency-Modulated Tones by Dolphins (Tursiops truncatus) (Abstract) Abstracts of the Seventh Biennial Conference on the Biology of Marine Mammals. Soc. Mar. 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.

Thomas, J. A. 1987. Factors That May Affect Sound Propagation from Acoustic Harassment Devices. Proceedings of the Acoustical Deterrents in Marine Mammal Conflicts with Fisheries, a Workshop Held February 17-18, 1986 at Newport, Oregon, eds. B. R. Mate and J. T. Harvey, Oregon State University, Publication no. ORESU- W-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., L. M. Ferm and V. B. Kuechle. 1987. Silence as an Antipredation Strategy by Weddell Seals. Antarctic Journal of the U.S., 22(5):232-234.

The hourly rate of underwater vocalizations over the day was collected near McMurdo Sound, Antarctica, from October through January for three seasons. In mid-December, for three years, the number of Weddell seal sounds decreased dramatically at the same time that killer whale and leopard seal vocalizations increased. The study proposes that as the two predatory species move near breeding colonies of Weddell seals, they shift from a highly vocal behavior to silence to avoid attracting attention to newly weaned seal pups.

Thomas, J. A., R. A. Puddicombe, M. George, and D. Lewis. 1988. Variations in Under- water 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.

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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, pp. 323-328, eds. P. E. Nachtigall and P. W. B. Moore, Plenum Press, New York.

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 echo- location. Some low-frequency and high-frequency components were present in the echolocation clicks.

Thomas, J. A., L. M. Ferm, and V. B. Kuechle. 1988. Patterns of Underwater Calls from Weddell Seals (Leptonychotes weddelli) During the Breeding Season at McMurdo Sound, Antarctica. Antarctic Journal of the U.S. 23(5):146-148.

Seasonal changes in the hourly rate of vocalizations by Weddell seals was documented by automated cassette recorders. The rates changed in a way that predicted the onset of reproductive activities such as pupping, weaning, mating, and dispersal.

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., and C. W. Turl. 2990. Echolocation Characteristics and Range Detection Threshold of a False Killer Whale (Pseudorca crassidens). In: Sensory Abilities of Cetaceans. pp. 321-334, eds. J. A. Thomas and R.A. Kastelein, Plenum Press, New York .

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, pp. 395-404, eds. J. A. Thomas and R, A. Kastelein, Plenum Press, New York.

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. Critical ratios ranged from

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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 broad- band 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. 0. 1965. Deep-water Recordings of Pinniped Sounds. Addendum to Proc. 2nd Conf. Biol. Sonar and Diving Mammals, 11 pp, Stanford Research Institute, Menlo Park, California.

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. 0., and W. C. Cummings. 1969. Sound Production of the Finback Whale (Balaenoptera physalus) and Eden's whale (B. edeni) in the Gulf of California. (Abstract) Proc. 6th Conf. Biol. Sonar and Diving Mammals, Stanford Research Institute, p. 109.

Describes powerful, low-frequency sounds from two species of whales found in the Gulf of California. Finback signals ranged from 20-100 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. 0. 1978. Underwater Repetitive Mammal Sound Sequences in the Bering Strait. (Abstract) Jour. Acoust. Soc. Am. vol. 64, suppl. 1, p. 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. 0., 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 2981. Sounds of five whale species (humpback, fin, blue, sperm, and pilot)

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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. (Abstract) Jour. Acoust. Soc. Am. vol. 74, suppl. 1, p. 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 presences 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, Symposium on Noise and Marine Mammals, pp. 89-93, eds. W. M. Sackinger, M. O. Jeffries, J. L. Imm and S. D. Treacy, Geophys. Inst., Univ. Alaska.

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

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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)," ed. by T. G. Smith, D. J. St. Aubin, and J. R. Geraci, Canadian Bulletin of Fisheries and Aquatic Sciences 224:119-128.

A review. The beluga's bioacoustic abilities are not fully known, but information suggests their 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 far 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 O-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.

Wenz, G. M. 1964. Curious noises and the sonic environment in the ocean. In: Marine Bio-Acoustics, vol. 1, pp. 101-119, ed. W. N. Tavolga, Pergamon Press, Elmsford, NY.

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. 1971. The Cochlea of the Dolphin (Tursiops truncatus): Hair Cells and Ganglion Cells. Proc. Nat. Acad. Sci. USA 68(12):2908-2912.

The large number of hair cells found suggests a high order of auditory proficiency, and the large ratio of ganglion cells to hair cells suggests an unusual ability to utilize auditory information.

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Wever, E. G., J. G. McCormick, J. Palin, and S. H. Ridgway. 1971. The Cochlea of the dolphin (Tursiops truncatus): General Morphology. Proc. Nat. Acad. Sci. USA 68(10): 2381-2385.

Describes the microscopic structure of the cochlea and discusses features believed to represent adaptations for the reception of high-frequency sounds.

Wever, E. G., J. C. McCormick, J. Palin, and S. H. Ridgway. 1971. Cochlea of the Dolphin (Tursiops truncatus): The Basilar Membrane. Proc. Nat. Acad. Sci. USA 68(11):2708-2711.

Describes the microscopic structure of the basilar membrane and notes features suggesting unusual capabilities of pitch discrimination at very high frequencies.

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, pp. 381-425, eds. R. G. Busnel and J. F. Fish, Plenum Press, New York.

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 adaptability, sensory integration, and versatility of sonar system.

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