Paul E Nachtigall

University of Hawaiʻi at Mānoa | UH Manoa · Institute of Marine Biology

The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

A correction to this paper has been published: https://doi.org/10.1007/s00359-021-01488-0

The acoustic startle reflex is an oligo-synaptic reflex arc elicited by rapid-onset sounds. Odontocetes evolved a range of specific auditory adaptations to aquatic hearing and echolocation, e.g. the ability to downregulate their auditory sensitivity when emitting clicks. However, it remains unclear whether these adaptations also led to changes of t...

Toothed whales possess a sophisticated biosonar system by which ultrasonic clicks are projected in a highly directional transmission beam. Beam directivity is an important biosonar characteristic that reduces acoustic clutter and increases the acoustic detection range. This study measured click characteristics and the transmission beam pattern from...

Odontocete marine mammals explore the environment by rapidly producing echolocation signals and receiving the corresponding echoes, which likewise return at very rapid rates. Thus, it is important that the auditory system has a high temporal resolution to effectively process and extract relevant information from click echoes. This study used audito...

Broadband active sonar systems estimate range from time delay and velocity from Doppler shift. Relatively little attention has been paid to how the received echo spectrum encodes information about the bearing of an object. This letter derives the bearing Fisher Information encoded in the frequency dependent transmitter beampattern. This leads to a...

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 recordi...

The biosonar of odontocetes processes echo signals with a wide range of echo levels. Several mechanisms that serve to compensate for the echo-level variation (biosonar gain control) have been revealed: (1) the adjustment of the emitted sonar pulse levels (the longer the distance to the target, the higher the level of the emitted pulse), (2) the rel...

Sensitivity to the local underwater acoustic stimulation of the ventro-lateral head surface was investigated in a bottlenose dolphin (Tursiops truncatus). The stimuli were tone pip trains of carrier frequencies ranging from 32 to 128 kHz with a pip rate of 1 kHz. Auditory evoked potentials (the rate following responses) were recorded. For all the t...

Sensitivity to the local underwater acoustic stimulation of the ventro-lateral head surface was investigated in a bottlenose dolphin (Tursiops truncatus). The stimuli were tone pip trains of carrier frequencies ranging from 32 to 128 kHz with a pip rate of 1 kHz. Auditory evoked potentials (the rate following responses) were recorded. For all the t...

On-animal suction cups with embedded hydrophones allow examination of how signals on the forehead of echolocating odontocetes relate to the internal anatomical structure and the transmission beampattern. Risso’s dolphin (Grampus griseus) is an interesting species for this investigation due to the presence of a unique vertical groove in the middle o...

The sonar of odontocetes processes echo signals within a wide range of echo levels. The level of echoes varies by tens of dB depending on the the target strength, the distance to the target, and the sound absorption by the media. The sonar of odontocetes has several mechanisms to compensate for the echo-level variation (gain control): (i) variation...

Transmission beam characteristics have been described in a small number of odontocete species, providing insight into the biological and ecological factors that have influenced the design of the outgoing echolocation beam. The current study measured the on-axis spectral characteristics and transmission beam pattern of echolocation clicks from a sma...

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 Protecti...

Hearing sensitivity, during trials in which a warning sound preceding a loud sound, was investigated in two harbor porpoises (Phocoena phocoena). Sensitivity was measured using pip-train test stimuli and auditory evoked potential recording. When a hearing test/warning stimulus, with a frequency of either 45 or 32 kHz, preceded a loud 32 kHz tone wi...

Ice-dwelling beluga whales are increasingly being exposed to anthropogenic loud sounds. Beluga's hearing sensitivity measured during a warning sound just preceding a loud sound was tested using pip-train stimuli and auditory evoked potential recording. When the test/warning stimulus with a frequency of 32 or 45 kHz preceded the loud sound with a fr...

The hearing sensitivity of a bottlenose dolphin for a warning sound, when the exact time of the arrival of a loud sound could, or could not, be predicted was measured. Sensitivity was measured when the time of the onset of the loud sound was randomly varied (random-variation sessions) and when the time of the onset of the loud and the pattern of st...

The echolocation system of the Risso's dolphin (Grampus griseus) remains poorly studied compared to other odontocete species. In this study, echolocation signals were recorded from a stationary Risso's dolphin with an array of 16 hydrophones and the two-dimensional beam shape was explored using frequency-dependent amplitude plots. Click source para...

Blast fishing is an illegal and unsustainable practice that is often reported in Southeast Asia and Africa. Its impact on fish and reef-building corals is well documented, yet there is limited information on the effects on other larger species and near-shore predators. In recent years, several marine mammal strandings in the Philippines have coinci...

The echolocation system of the Risso's dolphin (Grampus griseus) remains poorly studied compared to other odontocete species. In this study, echolocation signals were recorded from a stationary Risso's dolphin with an array of 16 hydrophones and the two-dimensional beam shape was explored using frequency-dependent amplitude plots. Click source para...

Understanding the hearing of marine mammals has been a priority to quantify and mitigate the impact of anthropogenic sound on these apex predators. Yet our knowledge of cetacean hearing is still limited to a few dozen species, therefore compromising any attempt to design adaptive management strategies. The use of auditory evoked potentials allows s...

Stranded whales and dolphins have sometimes been associated with loud anthropogenic sounds. Echolocating whales produce very loud sounds themselves and have developed the ability to protect their hearing from their own signals. A false killer whale's hearing sensitivity was measured when a faint warning sound was given just before the presentation...

A growing demand for sustainable energy has led to an increase in construction of offshore windfarms. Guishan windmill farm will be constructed in the Pearl River Estuary, China, which sustains the world's largest known population of Indo-Pacific humpback dolphins (Sousa chinensis). Dolphin conservation is an urgent issue in this region. By using p...

Experts survey the latest research on dolphin communication and cognition, offering a comprehensive reference to findings in the laboratory and from the field. Dolphin researchers have collected an impressive amount of data over the last twenty years, thanks to advances in technology for monitoring, recording, and analyzing dolphin behavior as well...

The odontocete sound production system is complex and composed of tissues, air sacs, and a fatty melon. Previous studies suggested that the emitted sonar beam might be actively focused, narrowing depending on target distance. In this study, we further tested this beam focusing hypothesis in a false killer whale. Using three linear arrays of hydroph...

Studies have shown that echolocation signals of some odontocete species are projected in both single and sometimes vertically dual-lobed beam shapes. In this study, the echolocation beam of a Risso's dolphin (Grampus griseus) was measured from a captive individual ensonifying an underwater target. Clicks were recorded with an array of 16 hydro...

The frequency specificity of conditioned dampening of hearing, when a loud sound is preceded by a warning sound, was investigated in a bottlenose dolphin. The loud sounds were 5-s tones of 16, 22.5, or 32 kHz, SPL of 165 dB rms re 1 μPa. Hearing sensitivity was tested at the same three frequencies. Hearing sensitivity was measured using pip-train t...

Echolocating bats and toothed whales probe their environment with ultrasonic sound pulses, using returning echoes to navigate and find prey in a process that appears to have resulted from a remarkable convergence of the two taxa. Here we report the first detailed quantification of echolocation behaviour during prey capture in the most studied delph...

The odontocete sound production system is complex and composed of tissues, air sacs, and a fatty melon. Previous studies suggested that the emitted sonar beam might be actively focused, narrowing depending on target distance. In this study, we further tested this beam focusing hypothesis in a false killer whale (Pseudorca crassidens) in a laborator...

Echolocating animals adjust the transmit intensity and receive sensitivity of their sonar in order to regulate the sensation level of their echoes; this process is often termed automatic gain control. Gain control is considered not to be under the animal's cognitive control, but previous investigations studied animals ensonifying targets or hydroph...

Echolocation comprises an animal sending out signals and listening for the echoes bouncing off objects in the environment. Given the ease of recording outgoing clicks and cries, more information is known about the outgoing signals than what animals hear of the echoes. Loud outgoing signals produce pronounced echoes but also create problems for hear...

The need for an updated review of echolocation is obvious in light of the rapid development in the field. Equipment has improved dramatically to allow unprecedented level of control also in field experiments. Also, the active acoustic orientation of bats and dolphins provide a unique window into adaptive perception processes, making echolocators at...

The conditioned change in hearing sensitivity during a warning sound preceding a loud sound was investigated in the bottlenose dolphin. Hearing sensitivity was measured using pip-train test stimuli and auditory evoked potential recording. When the test/warning stimulus with a frequency of 22.5 or 32 kHz preceded the loud sound with a frequency of 2...

Invariant target recognition by sonar requires assessment of the target strength invariably of distance despite wide variation of the echo level. Information on the echo delay and the level of the emitted pulse allows computing of the target strength. The question is: which particular mechanisms perform this computation in the biosonar of odontocet...

Work on hearing during echolocation has demonstrated that a whale was capable of changing its hearing sensitivity while it echolocated, perhaps to protect its hearing from its own intense emitted pulses. Would a whale similarly change hearing sensitivity when warned prior to receiving a loud sound? Hearing was measured using auditory evoked potenti...

Bats and odondoctes have evolved the ability to use echolocation to find objects in their environments. And, despite there being substantial differences in their environments, there are substantial similarities, as well as any number of fascinating differences, in how members of these two groups produce, use, and process biosonar signals. Chapters...

Although termed "automatic gain control," previous field and laboratory investigations into source level distance compensation in bats and odontocetes have relied on animals echolocating targets or arrays at predictable distances. To test the "automatic" nature of gain control in the bottlenose dolphin, the source level distance compensation was me...

The possibility of conditioned dampening of whale hearing thresholds, when a loud sound is preceded by a warning sound, was investigated. The loud sound was a tone of 20 kHz, 170 dB re 1 μPa, 5s. Hearing sensitivity was measured using pip-train test stimuli and auditory evoked potential recording. The same test sounds served as warning sounds. The...

Sensitivity of echolocating dolphins to phase changes within echoes may be a vital piece of information when constructing echolocation models. Previous experiments have yielded ambiguous results leaving it unclear what cues might have been used by passively listening dolphins to discriminate between different phase altered signals. This study used...

The sonar of odontocetes processes echo-signals within a wide range of echo levels. The level of echoes varies widely by tens of decibels depending on the level of the emitted sonar pulse, the target strength, the distance to the target, and the sound absorption by the water media. The auditory system of odontocetes must be capable of effective per...

A false killer whale's (Pseudorca crassidens) sonar clicks and auditory evoked potentials (AEPs) were recorded during echolocation with simulated echoes in two series of experiments. In the first, both the echo delay and transfer factor (which is the dB-ratio of the echo sound-pressure level to emitted pulse source level) were varied randomly from...

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 tig...

High-frequency auditory filter shapes of an Atlantic bottlenose dolphin (Tursiops truncatus) were measured using a notched noise masking source centered on pure tone signals at frequencies of 40, 60, 80 and 100 kHz. A dolphin was trained to swim into a hoop station facing the noise/signal transducer located at a distance of 2 m. The dolphin's maske...

Some odontocetes and bats vary both click intensity and receiver sensitivity during echolocation, depending on target range. It is not known how this so-called automatic gain control is regulated by the animal. The source level of consecutive echolocation clicks from a harbour porpoise was measured with a hydrophone array while the animal detected...

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-...

Transmitting biosonar clicks and auditory evoked potential (AEP) responses triggered by the clicks were synchronously recorded during echolocation in an Atlantic bottlenose dolphin (Tursiops truncatus) trained to wear suction-cup EEG electrodes and to detect targets by echolocation. Three targets with target strengths of 34, 28 and 22 dB were used...

We have been examining the hearing of both the outgoing clicks and the returning echoes of actively echolocating odontocetes using evoked auditory potential techniques. In order to protect themselves from the loud outgoing sound while still maximizing the hearing of the acoustic echo return, odontocete echolocators appear to have developed both pas...

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 bea...

Animals that use echolocation (biosonar) listen to acoustic signals with a large range of intensities, because echo levels vary with the fourth power of the animal's distance to the target. In man-made sonar, engineers apply automatic gain control to stabilize the echo energy levels, thereby rendering them independent of distance to the target. Bot...

Emitted biosonar clicks and auditory evoked potential (AEP) responses triggered by the clicks were synchronously recorded during echolocation in an Atlantic bottlenose dolphin (Tursiops truncatus) trained to wear suction-cup EEG electrodes and to detect targets by echolocation. Three targets with target strengths of -34, -28, and -22 dB were used a...

Dolphins and toothed whales (odontocetes) possess highly developed sound production systems and hearing capabilities (Au 1993; Au et al. 2000). Because sound is transmitted much more efficiently than light and other possible stimuli through water, hearing plays a fundamental role as a primary sensory modality in dolphins and toothed whales and func...

Anthropogenic noise may interfere with active echolocation, which is the primary foraging tool for odontocete cetaceans. Our work on temporary threshold shifts (Mooney et al. 2009a; Nachtigall et al. 2003, 2004) has shown that either lower levels of anthropogenic noise presented for long time periods or intense sonar pings for short time periods (M...

Hearing is a primary sense in many marine animals, and we now have a reasonable understanding of what stimuli generate clear responses, the frequency range of sensitivity, expected threshold values, and mechanisms of sound detection for several species of marine mammals and fishes ( Au et al. 2000; Fay 1988). For marine invertebrates, our knowledge...

The improvement in tagging technology and passive listening devices has allowed researchers to measure the echolocation clicks of many species of free-ranging odontocetes. Although the data collected by these instruments provide valuable information on the clicks these animals produce, these tags cannot provide information on the hearing abilities...

The hearing of marine mammals has been extensively studied in the last decades and has focused primarily on species available in captivity such as the bottlenose dolphin Tursiops truncatus. Recent work has shown that mass stranding events could be related to anthropogenic sound exposure such as naval sonar activities, seismic surveys, or oil drilli...

Recent studies indicate some odontocetes may produce echolocation beams with a dual-lobed vertical structure. The shape of the odontocete echolocation beam was further investigated in a false killer whale performing an echolocation discrimination task. Clicks were recorded with an array of 16 hydrophones and frequency-dependent amplitude plots were...

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 anticipa...

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 bet...

The auditory filter shape of delphinid odontocetes was previously considered to be typically mammalian constant-quality in which filter bandwidths increase proportionally with frequency. Recent studies with porpoises demonstrate constant-bandwidth portions of the auditory filter. The critical ratios for a bottlenose dolphin were measured between 40...

A 2D array of hydrophones was created to determine the spatial distribution of frequencies within the echolocation beam of a Tursiops truncatus. This Tursiops was shown previously to only pay attention to frequencies between 29 and 42 kHz while echolocating. It was found that the 30 kHz frequency was tightly focused, and the spatial location of the...

Auditory evoked potentials (AEP) were recorded during echolocation in a false killer whale Pseudorca crassidens. An electronically synthesized and played-back (simulated) echo was triggered by an emitted biosonar pulse, and its intensity was proportional to that of the emitted click. The delay and transfer factor of the echo relative to the emitted...

Quantifying and understanding the impact of anthropogenic sound on marine mammals has been the focus of many researchers both in laboratory settings as well as in the field. This study presents the audiogram of a sub-adult Blainville's beaked whale that stranded in Hawaii. The hearing measurements were conducted using the non-invasive auditory brai...

Auditory evoked potential (AEP) responses were recorded during echolocation in an Atlantic bottlenose dolphin (Tursiops truncatus) trained to accept suction-cup EEG electrodes and detect targets by echolocation. AEP recording was triggered by the echolocation clicks of the animal. Three targets with target strengths of -34, -28 and -22 dB were used...

Odontocete cetaceans may differ from most mammals in their response to noise. A close look at the published data [Popov et al. (2006)] of the critical bandwidths of two species of porpoises, the harbor porpoise (Phocaena phocoena) and the finless porpoise (Neophocaena phocaenoides), shows constant bandwidth critical bands in the high frequency area...

High‐frequency hearing loss has been correlated with a reduction both in echolocation click parameters and in echolocation discrimination abilities in a false killer whale. During a 15‐year time period, the whale demonstrated a significant decrease in peak frequency, center frequency, and source level of outgoing clicks between two studies. Echoloc...

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 audito...

Although hearing has been described for many underwater species, there is much debate regarding if and how cephalopods detect sound. Here we quantify the acoustic sensitivity of the longfin squid (Loligo pealeii) using near-field acoustic and shaker-generated acceleration stimuli. Sound field pressure and particle motion components were measured fr...