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Auditory Masking in Sea Lions, Seals...

Jones, Ryan Alexander,

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Auditory Masking in Sea Lions, Seals, and Walruses /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Auditory Masking in Sea Lions, Seals, and Walruses // Ryan Alexander Jones.
Author:	Jones, Ryan Alexander,
Description:	1 electronic resource (160 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-07, Section: B.
Contained By:	Dissertations Abstracts International86-07B.
Subject:	Acoustics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31763675
ISBN:	9798302851536

Auditory Masking in Sea Lions, Seals, and Walruses /
Jones, Ryan Alexander,

Auditory Masking in Sea Lions, Seals, and Walruses /Ryan Alexander Jones. - 1 electronic resource (160 pages)

Source: Dissertations Abstracts International, Volume: 86-07, Section: B.

Despite its importance within marine habitats, most of what we know about auditory masking is based on terrestrial species and theoretical assumptions about signal processing in animals. To fill data gaps and improve models that predict active listening space for marine mammals, I have measured hearing thresholds for tonal sounds with highly trained sea lions, walruses, and seals in the presence of precisely and experimentally varied background noise conditions. My aim is to provide empirical measurements of frequency-dependent masking parameters to inform a quantitative understanding of the acoustic scenarios encountered by free-ranging individuals. Three frequency-dependent aspects of masking are considered: critical ratios, critical bandwidths, and masker level effects. Critical ratios (CR), or the signal-to-noise ratios required for auditory detection of pure tones embedded in controlled, spectrally-flat noise, were measured for sea lion and walrus subjects across a frequency span from 0.2 to 16 kHz. Despite differences in hearing sensitivity, these masking metrics were similar for the subjects and followed expected frequency-dependent trends observed in terrestrial carnivores. When compared to published data for seals, sea lion and walrus CRs were generally higher, indicating that, among these marine Carnivores, seals are especially adapted for hearing in noise. To evaluate how the spectral content of noise contributes to masking, I determined the frequency bandwidth of noise that interferes with the detection of a given tonal signal, the 'critical bandwidth' (CBW). I conducted hearing measurements with three subjects-a sea lion, walrus, and seal-while varying the frequency content of surrounding noise. The study subjects showed an expected increase in absolute CBW with increasing frequency. While data for the sea lion and walrus were similar, the seal exhibited narrower CBWs that increased as a constant percentage of center frequency, further suggesting additional specialization for hearing in noise for this group. Finally, to explore how noise level contributes to masking, I conducted a series of tone detection measurements with one California sea lion in a highly controlled acoustic environment. Across experimental trials, I gradually increased the amplitude of surrounding noise from a level of no effect to capture masking onset. The data revealed a frequency-and bandwidth-dependent transition zone that occurs before complete masking is evident. The reported masking parameters provide insight into how some marine mammals hear within noisy conditions. These data, obtained using behavioral, psychoacoustic methods, can be applied to estimate masking effects for amphibious marine carnivores listening in air or water. Further, because they extend to lower frequencies where noise tends to be high and few hearing data are available, these results have clear and actionable outcomes and implications for real-world scenarios and conservation. The findings identify the frequencies where these species are most vulnerable to noise, highlight differences in auditory biology among pinniped lineages, and enable improved predictions of the extent of masking in marine environments dominated by natural and anthropogenic noise.

English

ISBN: 9798302851536Subjects--Topical Terms:

879105
Acoustics.
Subjects--Index Terms:

Hearing

Auditory Masking in Sea Lions, Seals, and Walruses /
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520 $a Despite its importance within marine habitats, most of what we know about auditory masking is based on terrestrial species and theoretical assumptions about signal processing in animals. To fill data gaps and improve models that predict active listening space for marine mammals, I have measured hearing thresholds for tonal sounds with highly trained sea lions, walruses, and seals in the presence of precisely and experimentally varied background noise conditions. My aim is to provide empirical measurements of frequency-dependent masking parameters to inform a quantitative understanding of the acoustic scenarios encountered by free-ranging individuals. Three frequency-dependent aspects of masking are considered: critical ratios, critical bandwidths, and masker level effects. Critical ratios (CR), or the signal-to-noise ratios required for auditory detection of pure tones embedded in controlled, spectrally-flat noise, were measured for sea lion and walrus subjects across a frequency span from 0.2 to 16 kHz. Despite differences in hearing sensitivity, these masking metrics were similar for the subjects and followed expected frequency-dependent trends observed in terrestrial carnivores. When compared to published data for seals, sea lion and walrus CRs were generally higher, indicating that, among these marine Carnivores, seals are especially adapted for hearing in noise. To evaluate how the spectral content of noise contributes to masking, I determined the frequency bandwidth of noise that interferes with the detection of a given tonal signal, the 'critical bandwidth' (CBW). I conducted hearing measurements with three subjects-a sea lion, walrus, and seal-while varying the frequency content of surrounding noise. The study subjects showed an expected increase in absolute CBW with increasing frequency. While data for the sea lion and walrus were similar, the seal exhibited narrower CBWs that increased as a constant percentage of center frequency, further suggesting additional specialization for hearing in noise for this group. Finally, to explore how noise level contributes to masking, I conducted a series of tone detection measurements with one California sea lion in a highly controlled acoustic environment. Across experimental trials, I gradually increased the amplitude of surrounding noise from a level of no effect to capture masking onset. The data revealed a frequency-and bandwidth-dependent transition zone that occurs before complete masking is evident. The reported masking parameters provide insight into how some marine mammals hear within noisy conditions. These data, obtained using behavioral, psychoacoustic methods, can be applied to estimate masking effects for amphibious marine carnivores listening in air or water. Further, because they extend to lower frequencies where noise tends to be high and few hearing data are available, these results have clear and actionable outcomes and implications for real-world scenarios and conservation. The findings identify the frequencies where these species are most vulnerable to noise, highlight differences in auditory biology among pinniped lineages, and enable improved predictions of the extent of masking in marine environments dominated by natural and anthropogenic noise.
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650 4 $a Aquatic sciences. $3 3174300
650 4 $a Biological oceanography. $3 2122748
653 $a Hearing
653 $a Marine mammals
653 $a Noise
653 $a Pinnipeds
653 $a Psychophysics
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690 $a 0416
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710 2 $a University of California, Santa Cruz. $b Ocean Sciences. $e degree granting institution. $3 3816884
720 1 $a Reichmuth, Colleen $e degree supervisor.
720 1 $a Friedlaender, Ari $e degree supervisor.
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