Masking release at 4 and 32 kHz in harbor seals associated with sinusoidal amplitude-modulated masking noise.

Masking can reduce the efficiency of communication and prey and predator detection. Most underwater sounds fluctuate in amplitude, which may influence the amount of masking experienced by marine mammals. The hearing thresholds of two harbor seals for tonal sweeps (centered at 4 and 32 kHz) masked by sinusoidal amplitude modulated (SAM) Gaussian one-third octave noise bands centered around the narrow-band test sweep frequencies, were studied with a psychoacoustic technique.

Masking release at 4 kHz in harbor porpoises (Phocoena phocoena) associated with sinusoidal amplitude-modulated masking noise.

Acoustic masking reduces the efficiency of communication, prey detection, and predator avoidance in marine mammals. Most underwater sounds fluctuate in amplitude. The ability of harbor porpoises (Phocoena phocoena) to detect sounds in amplitude-varying masking noise was examined.

Temporary hearing threshold shift in harbor seals (Phoca vitulina) due to one-sixth-octave noise bands centered at 0.5, 1, and 2 kHz.

This study concludes a larger project on the frequency-dependent susceptibility to noise-induced temporary hearing threshold shift (TTS) in harbor seals (Phoca vitulina). Here, two seals were exposed to one-sixth-octave noise bands (NBs) centered at 0.5, 1, and 2 kHz at several sound exposure levels (SELs, in dB re 1 μPas).

Lack of reproducibility of temporary hearing threshold shifts in a harbor porpoise after exposure to repeated airgun sounds.

Noise-induced temporary hearing threshold shift (TTS) was studied in a harbor porpoise exposed to impulsive sounds of scaled-down airguns while both stationary and free-swimming for up to 90 min. In a previous study, ∼4 dB TTS was elicited in this porpoise, but despite 8 dB higher single-shot and cumulative exposure levels (up to 199 dB re 1 μPas) in the present study, the porpoise showed no significant TTS at hearing frequencies 2, 4, or 8 kHz. There were no changes in the study animal's audiogram between the studies or significant differences in the fatiguing sound that could explain the difference, but audible and visual cues in the present study may have allowed the porpoise to predict when the fatiguing sounds would be produced.

Temporary hearing threshold shift in harbor seals (Phoca vitulina) due to a one-sixth-octave noise band centered at 32 kHz.

Two female harbor seals were exposed for 60 min to a continuous one-sixth-octave noise band centered at 32 kHz at sound pressure levels of 92 to 152 dB re 1 μPa, resulting in sound exposure levels (SELs) of 128 to 188 dB re 1 μPas. This was part of a larger project determining frequency-dependent susceptibility to temporary threshold shift (TTS) in harbor seals over their entire hearing range. After exposure, TTSs were quantified at 32, 45, and 63 kHz with a psychoacoustic technique.

Temporary hearing threshold shift in harbor seals (Phoca vitulina) due to a one-sixth-octave noise band centered at 40 kHz.

As part of a series of studies to determine frequency-dependent susceptibility to temporary hearing threshold shifts (TTS), two female harbor seals (F01 and F02) were exposed for 60 min to a one-sixth-octave noise band centered at 40 kHz at mean sound pressure levels ranging from 126 to 153 dB re 1 μPa [mean received sound exposure level (SEL) range: 162-189 dB re 1 μPas]. TTSs were quantified at 40, 50, and 63 kHz within 1-4 min of the exposure for F02 and within 12-16 min of the exposure for F01. In F02, significant TTS (1-4 min post exposure) occurred at 40 kHz with SELs of ≥183 dB re 1 μPas and at 50 kHz with SELs of ≥174 dB re 1 μPas.

Temporary hearing threshold shift in harbor seals (Phoca vitulina) due to a one-sixth-octave noise band centered at 16 kHz.

Temporary hearing threshold shifts (TTSs) were investigated in two adult female harbor seals after exposure for 60 min to a continuous one-sixth-octave noise band centered at 16 kHz (the fatiguing sound) at sound pressure levels of 128-149 dB re 1 μPa, resulting in sound exposure levels (SELs) of 164-185 dB re 1 μPas. TTSs were quantified at the center frequency of the fatiguing sound (16 kHz) and at half an octave above that frequency (22.4 kHz) by means of a psychoacoustic hearing test method.

Acoustic reflectivity of a harbor porpoise (Phocoena phocoena).

Acoustic backscatter measurements were conducted on a stationary harbor porpoise (Phocoena phocoena) under controlled conditions. The measurements were made with the porpoise in the broadside aspect using three different types of signals: (1) a 475 μs linear frequency-modulated (FM) pulse with a frequency range from 23 to 160 kHz; (2) a simulated bottlenose dolphin (Tursiops "truncates") click with a peak frequency of 120 kHz; and (3) a simulated killer whale (Orcinus orca) click with a peak frequency of 60 kHz. The measurement with the FM pulse indicated that the mean target strength at the broadside aspect decreased from -26 to -50 dB as the frequency increased from 23 to 120 kHz in a nearly linear fashion (on a logarithm plot).

Frequency of greatest temporary hearing threshold shift in harbor seals (Phoca vitulina) depends on fatiguing sound level.

Harbor seals may suffer hearing loss due to intense sounds. After exposure for 60 min to a continuous 6.5 kHz tone at sound pressure levels of 123-159 dB re 1 µPa, resulting in sound exposure levels (SELs) of 159-195 dB re 1 μPas, temporary threshold shifts (TTSs) in two harbor seals were quantified at the center frequency of the fatiguing sound (6.

Effect of pile-driving sounds on harbor seal (Phoca vitulina) hearing.

Seals exposed to intense sounds may suffer hearing loss. After exposure to playbacks of broadband pile-driving sounds, the temporary hearing threshold shift (TTS) of two harbor seals was quantified at 4 and 8 kHz (frequencies of the highest TTS) with a psychoacoustic technique. The pile-driving sounds had: a 127 ms pulse duration, 2760 strikes per h, a 1.

Hearing thresholds, for underwater sounds, of harbor seals (Phoca vitulina) at the water surface.

High-amplitude impulsive sounds produced by pile driving and airguns may result in hearing damage in nearby seals. By swimming at the water surface, seals may reduce their exposure to underwater sound, as sound pressure levels (SPLs) are often lower just below the surface than deeper in the water column. Seals can make physiological adjustments such that they can switch between having maximum sensitivity for either aerial or underwater sounds.

Temporary hearing threshold shift in a harbor porpoise (Phocoena phocoena) after exposure to multiple airgun sounds.

In seismic surveys, reflected sounds from airguns are used under water to detect gas and oil below the sea floor. The airguns produce broadband high-amplitude impulsive sounds, which may cause temporary or permanent threshold shifts (TTS or PTS) in cetaceans. The magnitude of the threshold shifts and the hearing frequencies at which they occur depend on factors such as the received cumulative sound exposure level (SELcum), the number of exposures, and the frequency content of the sounds.

Effects of exposure to sonar playback sounds (3.5 - 4.1 kHz) on harbor porpoise (Phocoena phocoena) hearing.

Safety criteria for naval sonar sounds are needed to protect harbor porpoise hearing. Two porpoises were exposed to sequences of AN/SQS-53C sonar playback sounds (3.5-4.

Spatial avoidance to experimental increase of intermittent and continuous sound in two captive harbour porpoises.

The continuing rise in underwater sound levels in the oceans leads to disturbance of marine life. It is thought that one of the main impacts of sound exposure is the alteration of foraging behaviour of marine species, for example by deterring animals from a prey location, or by distracting them while they are trying to catch prey. So far, only limited knowledge is available on both mechanisms in the same species.

Acoustic dose-behavioral response relationship in sea bass (Dicentrarchus labrax) exposed to playbacks of pile driving sounds.

The foundations of offshore wind turbines are attached to the sea bed by percussion pile driving. Pile driving sounds may affect the behavior of fish. Acoustic dose-behavioral response relationships were determined for sea bass in a pool exposed for 20 min to pile driving sounds at seven mean received root-mean-square sound pressure levels [SPLrms; range: 130-166 dB re 1 μPa; single strike sound exposure level (SEL) range: 122-158; 6 dB steps].

Hearing thresholds of a male and a female harbor porpoise (Phocoena phocoena).

To study intra-species variability in audiograms, the hearing sensitivity of a six-year-old female and a three-year-old male harbor porpoise was measured by using a standard psycho-acoustic technique under low ambient noise conditions. The porpoises' hearing thresholds for 13 narrow-band sweeps with center frequencies between 0.125 and 150 kHz were established.

Pile driving playback sounds and temporary threshold shift in harbor porpoises (Phocoena phocoena): Effect of exposure duration.

High intensity underwater sounds may cause temporary hearing threshold shifts (TTSs) in harbor porpoises, the magnitude of which may depend on the exposure duration. After exposure to playbacks of pile driving sounds, TTSs in two porpoises were quantified at 4 and 8 kHz with a psychophysical technique. At 8 kHz, the pile driving sounds caused the highest TTS.