The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Marlee Breese - One of the best experts on this subject based on the ideXlab platform.
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active echolocation beam focusing in the false killer whale Pseudorca crassidens
The Journal of Experimental Biology, 2012Co-Authors: Laura N Kloepper, Megan J Donahue, Paul E. Nachtigall, Marlee BreeseAbstract:SUMMARY The odontocete sound production system is highly complex and produces intense, directional signals that are thought to be focused by the melon and the air sacs. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. In this study we tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The data indicate that the false killer whale changes its beam size according to target distance and difficulty, which may be a strategy of maximizing the energy of the target echo. We propose that the animal is using a strategy of changing the focal region according to target distance and that this strategy is under active control.
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echolocation beam shape and focusing in the false killer whale Pseudorca crassidens
Journal of the Acoustical Society of America, 2012Co-Authors: Laura N Kloepper, Paul E. Nachtigall, Marlee BreeseAbstract:Odontocete echolocation signals are thought to be focused by the melon and air sacs, although active focusing has yet to be demonstrated empirically. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. Using a fine scale hydrophone array, we measured the shape of the echolocation beam and tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The false killer whale produced a single-lobed echolocation beam that changed in size depending on target distance and difficulty which may be a strategy of actively controlling the emitted beam to maximize energy of the target echo.
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similarities in echolocation strategy and click characteristics between a Pseudorca crassidens and a tursiops truncatus
Journal of the Acoustical Society of America, 2011Co-Authors: Stuart Ibsen, Whitlow W. L. Au, Paul E. Nachtigall, Jacqueline Krausenehring, Marlee BreeseAbstract:A previous comparative analysis of normalized click amplitude spectra from a Tursiops truncatus has shown that those frequencies with the lowest click-to-click variability in spectral content were the frequencies the animal paid attention to during target discrimination tasks. In that case, the dolphin only paid attention to the frequency range between 29–42 kHz which had a significantly higher degree of consistency in spectral content than frequencies above 42 kHz. Here it is shown that despite their morphological and behavioral differences, this same pattern of consistency was used by a Pseudorca crassidens performing a similar discrimination task. This comparison between species provides a foundation for using spectral level variability to determine the frequencies most important for echolocation in rare species and non-captive animals. Such results provide key information for successful management.
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spatial orientation of different frequencies within the echolocation beam of a tursiops truncatus and Pseudorca crassidens
Journal of the Acoustical Society of America, 2011Co-Authors: Stuart Ibsen, Laura N Kloepper, Marlee Breese, Paul E. Nachtigall, Jacqueline Krausenehring, Songhai Li, Stephanie VlachosAbstract:A two-dimensional array of 16 hydrophones was created to map the spatial distribution of different frequencies within the echolocation beam of a Tursiops truncatus and a Pseudorca crassidens. It was previously shown that both the Tursiops and Pseudorca only paid attention to frequencies between 29 and 42 kHz while echolocating. Both individuals tightly focused the 30 kHz frequency and the spatial location of the focus was consistently pointed toward the target. At 50 kHz the beam was less focused and less precisely pointed at the target. At 100 kHz the focus was often completely lost and was not pointed at the target. This indicates that these individuals actively focused the beam toward the target only in the frequency range they paid attention to. Frequencies outside this range were left unfocused and undirected. This focusing was probably achieved through sensorimotor control of the melon morphology and nasal air sacs. This indicates that both morphologically different species can control the spatial d...
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decreased echolocation performance following high frequency hearing loss in the false killer whale Pseudorca crassidens
The Journal of Experimental Biology, 2010Co-Authors: Laura N Kloepper, Paul E. Nachtigall, R Gisiner, Marlee BreeseAbstract:SUMMARY Toothed whales and dolphins possess a hypertrophied auditory system that allows for the production and hearing of ultrasonic signals. Although the fossil record provides information on the evolution of the auditory structures found in extant odontocetes, it cannot provide information on the evolutionary pressures leading to the hypertrophied auditory system. Investigating the effect of hearing loss may provide evidence for the reason for the development of high-frequency hearing in echolocating animals by demonstrating how high-frequency hearing assists in the functioning echolocation system. The discrimination abilities of a false killer whale (Pseudorca crassidens) were measured prior to and after documented high-frequency hearing loss. In 1992, the subject had good hearing and could hear at frequencies up to 100 kHz. In 2008, the subject had lost hearing at frequencies above 40 kHz. First in 1992, and then again in 2008, the subject performed an identical echolocation task, discriminating between machined hollow aluminum cylinder targets of differing wall thickness. Performances were recorded for individual target differences and compared between both experimental years. Performances on individual targets dropped between 1992 and 2008, with a maximum performance reduction of 36.1%. These data indicate that, with a loss in high-frequency hearing, there was a concomitant reduction in echolocation discrimination ability, and suggest that the development of a hypertrophied auditory system capable of hearing at ultrasonic frequencies evolved in response to pressures for fine-scale echolocation discrimination.
Paul E. Nachtigall - One of the best experts on this subject based on the ideXlab platform.
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Four odontocete species change hearing levels when warned of impending loud sound
Integrative Zoology, 2018Co-Authors: Paul E. Nachtigall, Alexander Ya Supin, Aude F Pacini, Ronald A. KasteleinAbstract:Hearing sensitivity change was investigated when a warning sound preceded a loud sound in the alse killer whale (Pseudorca crassidens) bottlenose dolphin (Tursiops truncatus) beluga whale (Delphinaperus leucas) and harbor porpoise (Phocoena phocoena). Hearing sensitivity was easured using pip-train test stimuli and auditory evoked potential recording. When the est/warning stimuli preceded a loud sound, hearing thresholds before the loud sound increased elative to the baseline by 13 to17 dB. Experiments with multiple frequencies of exposure and hift provided evidence of different amounts of hearing change depending on frequency, ndicating that the hearing sensation level changes were not likely due to a simple stapedial eflex. This article is protected by copyright. All rights reserved
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Echolocation detection of fishing hooks and implications for the Hawaiian longline fishery
Journal of the Acoustical Society of America, 2016Co-Authors: Aude F Pacini, Paul E. Nachtigall, Adam B. Smith, Owens, Stephanie VlachosAbstract:Interactions between marine mammals and fisheries have a biological and economic impact that is often detrimental to both fishermen and species of concern. False killer whale bycatch in the Hawaii longline fishery has exceeded the potential biological removal (PBR) triggering the designation of a take reduction team under the Marine Mammal Protection Act (MMPA). As an attempt to understand the importance of acoustic cues in depredation events, this study presents preliminary data looking at the echolocation ability of a false killer whale (Pseudorca crassidens) to detect a longline fishing hook at various distances. Using a go/no-go paradigm, the whale was trained to report the presence of the hook at distances varying in 50 cm increments. A total of 28 sessions of 25 trials each were collected and echolocation signals were recorded using a nine element acoustic array. Number of clicks, acoustic parameters, decision time and performance were recorded. The subject successfully reported the presence of the ...
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Gain variation in the odontocete biosonar when prior information about echo parameters is or is not available
2012Co-Authors: Alexander Ya Supin, Paul E. NachtigallAbstract:In a false killer whale Pseudorca crassidens, sonar clicks and auditory evoked potentials (AEP) were recorded during echolocation with simulated echo. In one experimental series, echo delay and transfer factor varied randomly from trial to trial (random presentation). With this manner of variation of echo parameters, the animal never could anticipated the parameter values. In another series, a combination of the echo delay and transfer factor was kept constant during several dozens of trials; therefore, the information about echo parameters was potentially available for the animal (ordered presentation). Mean click level decreased with shortening the delay and increasing the transfer factor, more at the ordered presentation rather than at random presentation. AEPs to the self-heard emitted clicks decreased with shortening the delay and increasing the echo level, equally at both random and ordered presentations. AEPs to echo increased with increasing the echo level, little dependent on echo delay at random...
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active echolocation beam focusing in the false killer whale Pseudorca crassidens
The Journal of Experimental Biology, 2012Co-Authors: Laura N Kloepper, Megan J Donahue, Paul E. Nachtigall, Marlee BreeseAbstract:SUMMARY The odontocete sound production system is highly complex and produces intense, directional signals that are thought to be focused by the melon and the air sacs. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. In this study we tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The data indicate that the false killer whale changes its beam size according to target distance and difficulty, which may be a strategy of maximizing the energy of the target echo. We propose that the animal is using a strategy of changing the focal region according to target distance and that this strategy is under active control.
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echolocation beam shape and focusing in the false killer whale Pseudorca crassidens
Journal of the Acoustical Society of America, 2012Co-Authors: Laura N Kloepper, Paul E. Nachtigall, Marlee BreeseAbstract:Odontocete echolocation signals are thought to be focused by the melon and air sacs, although active focusing has yet to be demonstrated empirically. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. Using a fine scale hydrophone array, we measured the shape of the echolocation beam and tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The false killer whale produced a single-lobed echolocation beam that changed in size depending on target distance and difficulty which may be a strategy of actively controlling the emitted beam to maximize energy of the target echo.
Laura N Kloepper - One of the best experts on this subject based on the ideXlab platform.
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active echolocation beam focusing in the false killer whale Pseudorca crassidens
The Journal of Experimental Biology, 2012Co-Authors: Laura N Kloepper, Megan J Donahue, Paul E. Nachtigall, Marlee BreeseAbstract:SUMMARY The odontocete sound production system is highly complex and produces intense, directional signals that are thought to be focused by the melon and the air sacs. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. In this study we tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The data indicate that the false killer whale changes its beam size according to target distance and difficulty, which may be a strategy of maximizing the energy of the target echo. We propose that the animal is using a strategy of changing the focal region according to target distance and that this strategy is under active control.
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echolocation beam shape and focusing in the false killer whale Pseudorca crassidens
Journal of the Acoustical Society of America, 2012Co-Authors: Laura N Kloepper, Paul E. Nachtigall, Marlee BreeseAbstract:Odontocete echolocation signals are thought to be focused by the melon and air sacs, although active focusing has yet to be demonstrated empirically. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. Using a fine scale hydrophone array, we measured the shape of the echolocation beam and tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The false killer whale produced a single-lobed echolocation beam that changed in size depending on target distance and difficulty which may be a strategy of actively controlling the emitted beam to maximize energy of the target echo.
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spatial orientation of different frequencies within the echolocation beam of a tursiops truncatus and Pseudorca crassidens
Journal of the Acoustical Society of America, 2011Co-Authors: Stuart Ibsen, Laura N Kloepper, Marlee Breese, Paul E. Nachtigall, Jacqueline Krausenehring, Songhai Li, Stephanie VlachosAbstract:A two-dimensional array of 16 hydrophones was created to map the spatial distribution of different frequencies within the echolocation beam of a Tursiops truncatus and a Pseudorca crassidens. It was previously shown that both the Tursiops and Pseudorca only paid attention to frequencies between 29 and 42 kHz while echolocating. Both individuals tightly focused the 30 kHz frequency and the spatial location of the focus was consistently pointed toward the target. At 50 kHz the beam was less focused and less precisely pointed at the target. At 100 kHz the focus was often completely lost and was not pointed at the target. This indicates that these individuals actively focused the beam toward the target only in the frequency range they paid attention to. Frequencies outside this range were left unfocused and undirected. This focusing was probably achieved through sensorimotor control of the melon morphology and nasal air sacs. This indicates that both morphologically different species can control the spatial d...
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decreased echolocation performance following high frequency hearing loss in the false killer whale Pseudorca crassidens
The Journal of Experimental Biology, 2010Co-Authors: Laura N Kloepper, Paul E. Nachtigall, R Gisiner, Marlee BreeseAbstract:SUMMARY Toothed whales and dolphins possess a hypertrophied auditory system that allows for the production and hearing of ultrasonic signals. Although the fossil record provides information on the evolution of the auditory structures found in extant odontocetes, it cannot provide information on the evolutionary pressures leading to the hypertrophied auditory system. Investigating the effect of hearing loss may provide evidence for the reason for the development of high-frequency hearing in echolocating animals by demonstrating how high-frequency hearing assists in the functioning echolocation system. The discrimination abilities of a false killer whale (Pseudorca crassidens) were measured prior to and after documented high-frequency hearing loss. In 1992, the subject had good hearing and could hear at frequencies up to 100 kHz. In 2008, the subject had lost hearing at frequencies above 40 kHz. First in 1992, and then again in 2008, the subject performed an identical echolocation task, discriminating between machined hollow aluminum cylinder targets of differing wall thickness. Performances were recorded for individual target differences and compared between both experimental years. Performances on individual targets dropped between 1992 and 2008, with a maximum performance reduction of 36.1%. These data indicate that, with a loss in high-frequency hearing, there was a concomitant reduction in echolocation discrimination ability, and suggest that the development of a hypertrophied auditory system capable of hearing at ultrasonic frequencies evolved in response to pressures for fine-scale echolocation discrimination.
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change in echolocation signals with hearing loss in a false killer whale Pseudorca crassidens
Journal of the Acoustical Society of America, 2010Co-Authors: Laura N Kloepper, Paul E. Nachtigall, Marlee BreeseAbstract:The echolocation signals of a false killer whale (Pseudorca crassidens) were collected during a wall thickness discrimination task and compared to clicks recorded during an identical experiment in 1992. During the sixteen year time period, the subject demonstrated a loss of high frequency hearing of about 70 kHz. Clicks between the two experiments were compared to investigate the effect of hearing loss on echolocation signals. There was a significant reduction in the peak frequency, center frequency and source level of clicks between the two time periods. Additionally, the subject currently produces more signals with low frequency peaks and fewer signals with high frequency peaks than she did in 1992. These results indicate the subject changed its echolocation signals to match its range of best hearing.
Jeffrey L Pawloski - One of the best experts on this subject based on the ideXlab platform.
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monitoring of progesterone in captive female false killer whales Pseudorca crassidens
General and Comparative Endocrinology, 1999Co-Authors: S Atkinson, Jeffrey L Pawloski, Paul E. Nachtigall, C Combelles, D L Vincent, Marlee BreeseAbstract:Abstract The present study describes progesterone profiles to enhance understanding of general reproductive patterns in three female captive false killer whales and analyzes potential relationships in progesterone concentrations between plasma, salivary, and ocular secretions. Plasma progesterone concentrations reflected ovarian activity for most of the year, with increased concentrations in the spring and summer, indicating that the two adult female false killer whales were spontaneous ovulators and seasonally polyestrus. Elevated progesterone concentrations were determined at intervals, for up to 10 consecutive months, in one female. There were also varying periods of no apparent ovarian activity from 3 to 10 consecutive months. Correlation coefficients between progesterone concentrations in plasma, salivary, and ocular secretions ranged between −0.23 and 0.16. It is concluded that blood collection should not be replaced by salivary or ocular secretion collection for the measurement of progesterone in the false killer whale.
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Acoustic effects of the ATOC signal (75 Hz, 195 dB) on dolphins and whales.
Journal of the Acoustical Society of America, 1997Co-Authors: Whitlow W. L. Au, Paul E. Nachtigall, Jeffrey L PawloskiAbstract:The Acoustic Thermometry of Ocean Climate (ATOC) program of Scripps Institution of Oceanography and the Applied Physics Laboratory, University of Washington, will broadcast a low-frequency 75-Hz phase modulated acoustic signal over ocean basins in order to study ocean temperatures on a global scale and examine the effects of global warming. One of the major concerns is the possible effect of the ATOC signal on marine life, especially on dolphins and whales. In order to address this issue, the hearing sensitivity of a false killer whale (Pseudorca crassidens) and a Risso’s dolphin (Grampus griseus) to the ATOC sound was measured behaviorally. A staircase procedure with the signal levels being changed in 1-dB steps was used to measure the animals’ threshold to the actual ATOC coded signal. The results indicate that small odontocetes such as the Pseudorca and Grampus swimming directly above the ATOC source will not hear the signal unless they dive to a depth of approximately 400 m. A sound propagation analys...
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The effects of the acoustic thermometry of ocean climate signals on dolphins and small whales
Journal of the Acoustical Society of America, 1995Co-Authors: Whitlow W. L. Au, Paul E. Nachtigall, Jeffrey L PawloskiAbstract:The acoustic thermometry of ocean climate (ATOC) program of Scripps Institute of Oceanography and the Applied Physics Laboratory, University of Washington, will broadcast a low‐frequency 75‐Hz phase‐modulated acoustic signal over ocean basins in order to study ocean temperatures on a global scale. One of the major concerns is the possible effect of the ATOC signal on marine life, especially on dolphins and whales. In order to address this issue, the hearing sensitivity of a false killer whale (Pseudorca crassidens) and a Risso’s dolphin (Grampus griseus) to the ATOC sound was measured behaviorally. A staircase procedure with the signal levels being changed in 1‐dB steps was used to measure the animals’ threshold to the actual ATOC coded signal. The results will be used to examine how the ATOC sound will affect the hearing capability of these small cetaceans. The relative effect of the ATOC sound will also be compared with effects from other sources of noise such as aircraft, ocean going ships, pleasure cr...
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Modulation rate transfer functions to low-frequency carriers in three species of cetaceans
Journal of Comparative Physiology A, 1995Co-Authors: W. F. Dolphin, W. W. L. Au, P. E. Nachtigall, Jeffrey L PawloskiAbstract:A temporal modulation rate transfer function (MRTF) is a quantitative description of the ability of a system to follow the temporal envelope of a stimulating waveform. In this study MRTFs were obtained from three cetacean species: the false killer whale Pseudorca crassidens ; the beluga whale Delphinapterus leucas ; and the bottlenosed dolphin Tursiops truncatus , using auditory-evoked potentials. Steady-state electrophysiological responses were recorded noninvasively from behaving, alert animals using suction cup electrodes placed on the scalp surface. Responses were elicited using continuous two-tone (TT) and sinusoidally amplitude-modulated (SAM) stimuli. MRTFs were obtained for modulation frequencies ranging from 18–4019 Hz using carrier and primary frequencies of 500, 1000, 4000, and 10000 Hz. Scalp potentials followed the low-frequency temporal envelope of the stimulating waveform; this envelope following response (EFR) was the dependent variable in all experiments. MRTFs were generally low-pass in shape with corner frequencies between approximately 1–2 kHz.
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echolocation signals and transmission beam pattern of a false killer whale Pseudorca crassidens
Journal of the Acoustical Society of America, 1995Co-Authors: Whitlow W. L. Au, Jeffrey L Pawloski, Michele Blonz, Paul E. Nachtigall, Robert C GisnerAbstract:The echolocation transmission beam pattern of a false killer whale (Pseudorca crassidens) was measured in the vertical and horizontal planes. A vertical array of seven broadband miniature hydrophones was used to measure the beam pattern in the vertical plane and a horizontal array of the same hydrophones was used in the horizontal plane. The measurements were performed in the open waters of Kaneohe Bay, Oahu, Hawaii, while the whale performed a target discrimination task. Four types of signals, characterized by their frequency spectra, were measured. Type‐1 signals had a single low‐frequency peak at 40±9 kHz and a low‐amplitude shoulder at high frequencies. Type‐2 signals had a bimodal frequency characteristic with a primary peak at 46±7 kHz and a secondary peak at 88±13 kHz. Type‐3 signals were also bimodal but with a primary peak at 100±7 kHz and a secondary peak at 49±9 kHz. Type‐4 signals had a single high‐frequency peak at 104±7 kHz. The center frequency of the signals were found to be linearly corre...
Whitlow W. L. Au - One of the best experts on this subject based on the ideXlab platform.
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similarities in echolocation strategy and click characteristics between a Pseudorca crassidens and a tursiops truncatus
Journal of the Acoustical Society of America, 2011Co-Authors: Stuart Ibsen, Whitlow W. L. Au, Paul E. Nachtigall, Jacqueline Krausenehring, Marlee BreeseAbstract:A previous comparative analysis of normalized click amplitude spectra from a Tursiops truncatus has shown that those frequencies with the lowest click-to-click variability in spectral content were the frequencies the animal paid attention to during target discrimination tasks. In that case, the dolphin only paid attention to the frequency range between 29–42 kHz which had a significantly higher degree of consistency in spectral content than frequencies above 42 kHz. Here it is shown that despite their morphological and behavioral differences, this same pattern of consistency was used by a Pseudorca crassidens performing a similar discrimination task. This comparison between species provides a foundation for using spectral level variability to determine the frequencies most important for echolocation in rare species and non-captive animals. Such results provide key information for successful management.
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Integration of real‐time odontocete call classification algorithm into PAMGUARD signal processing software.
Journal of the Acoustical Society of America, 2011Co-Authors: Michael Oswald, Julie N. Oswald, Marc O. Lammers, Shannon Rankin, Whitlow W. L. AuAbstract:Real‐time odontocete call classification algorithm (ROCCA) is a tool for real‐time acoustic species identification of delphinid whistles. Introduced in 2006 as MATLAB‐based software, ROCCA is currently being incorporated into PAMGUARD, a freely‐available, open source software package. ROCCA provides automated extraction of whistle contours from a spectrogram. It measures 54 whistle contour features including frequencies, slopes, duration, and variables related to the positions of inflection points and steps. ROCCA currently classifies whistles of seven species and one genus: Globicephala macrorhynchus, Pseudorca crassidens, Steno bredanensis, Stenella attenuata, S. coeruleoalba, S. longirostris, Tursiops truncatus, and Delphinus species. The classifier is a Random Forest trained on 2231 whistles collected over six cruises and 7 years in the eastern tropical Pacific Ocean. The original ROCCA classifier used a combination of discriminant function analysis and CART algorithms on 13 whistle contour features f...
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Seeing the species through the trees: Using Random Forest classification trees to identify species‐specific whistle types.
Journal of the Acoustical Society of America, 2011Co-Authors: Julie N. Oswald, Michael Oswald, Shannon Rankin, Jim V. Carretta, Whitlow W. L. AuAbstract:Acoustic identification of delphinid species is hampered by high variability in whistle characteristics. It is possible that not every whistle contains species‐specific information and that there are “species‐specific” whistle types. Random forest analysis was used to examine whistles of 8 species recorded in the eastern tropical Pacific Ocean (Delphinus species, Globicephala macrorhynchus, Pseudorca crassidens, Stenella attenuata, S. coeruleoalba, S. longirostris, Steno bredanensis, Tursiops truncatus). Fifty‐one variables were measured from 2176 whistles. The number of trees within a random forest that “voted” for the predicted species was used as a measure of the strength of classification. A whistle was considered strongly classified if the predicted species received at least 40% of the votes, even if the prediction was incorrect. The percent of whistles that were strongly classified ranged from 33% (S. longirostris) to 73% (G. macrorhynchus). Overall, 62% of strong whistles were correctly classified,...
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invariance of evoked potential echo responses to target strength and distance in an echolocating false killer whale
Journal of the Acoustical Society of America, 2005Co-Authors: Alexander Ya Supin, Paul E. Nachtigall, Whitlow W. L. Au, Marlee BreeseAbstract:Brain auditory evoked potentials (AEPs) were recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP collection was triggered by echolocation pulses transmitted by the animal. The target strength varied from −22 to −40 dB; the distance varied from 1.5 to 6 m. All the records contained two AEP sets: the first one of a constant latency (transmission-related AEP) and a second one with a delay proportional to the distance (echo-related AEP). The amplitude of echo-related AEPs was almost independent of both target strength and distance, though combined variation of these two parameters resulted in echo intensity variation within a range of 42 dB. The amplitude of transmission-related AEPs was independent of distance but dependent on target strength: the less the target strength, the higher the amplitude. Recording of transmitted pulses has not shown their intensity dependence on target strength. It is supposed that the consta...
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Acoustic effects of the ATOC signal (75 Hz, 195 dB) on dolphins and whales.
Journal of the Acoustical Society of America, 1997Co-Authors: Whitlow W. L. Au, Paul E. Nachtigall, Jeffrey L PawloskiAbstract:The Acoustic Thermometry of Ocean Climate (ATOC) program of Scripps Institution of Oceanography and the Applied Physics Laboratory, University of Washington, will broadcast a low-frequency 75-Hz phase modulated acoustic signal over ocean basins in order to study ocean temperatures on a global scale and examine the effects of global warming. One of the major concerns is the possible effect of the ATOC signal on marine life, especially on dolphins and whales. In order to address this issue, the hearing sensitivity of a false killer whale (Pseudorca crassidens) and a Risso’s dolphin (Grampus griseus) to the ATOC sound was measured behaviorally. A staircase procedure with the signal levels being changed in 1-dB steps was used to measure the animals’ threshold to the actual ATOC coded signal. The results indicate that small odontocetes such as the Pseudorca and Grampus swimming directly above the ATOC source will not hear the signal unless they dive to a depth of approximately 400 m. A sound propagation analys...
