Changes in masked thresholds of a harbour seal (<i>Phoca vitulina</i>) associated with angular separation of signal and noise sources

Turnbull, S. D.

doi:10.1139/z94-253

Cited by 22 publications

(15 citation statements)

References 17 publications

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“…In this paper we assume that marine mammals have the ability to spatially segregate signals and noise (e.g. Turnbull 1994, Holt & Schusterman 2007. We therefore include a representative term for signal directionality in our model of communication masking for free-ranging animals, but we do not give it an empirically informed value.…”

Section: Examplesmentioning

confidence: 99%

Acoustic masking in marine ecosystems: intuitions, analysis, and implication

Clark¹,

Ellison²,

Southall³

et al. 2009

Mar. Ecol. Prog. Ser.

460

369

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Acoustic masking from anthropogenic noise is increasingly being considered as a threat to marine mammals, particularly low-frequency specialists such as baleen whales. Low-frequency ocean noise has increased in recent decades, often in habitats with seasonally resident populations of marine mammals, raising concerns that noise chronically influences life histories of individuals and populations. In contrast to physical harm from intense anthropogenic sources, which can have acute impacts on individuals, masking from chronic noise sources has been difficult to quantify at individual or population levels, and resulting effects have been even more difficult to assess. This paper presents an analytical paradigm to quantify changes in an animal's acoustic communication space as a result of spatial, spectral, and temporal changes in background noise, providing a functional definition of communication masking for free-ranging animals and a metric to quantify the potential for communication masking. We use the sonar equation, a combination of modeling and analytical techniques, and measurements from empirical data to calculate time-varying spatial maps of potential communication space for singing fin (Balaenoptera physalus), singing humpback (Megoptera novaeangliae), and calling right (Eubalaena glacialis) whales. These illustrate how the measured loss of communication space as a result of differing levels of noise is converted into a time-varying measure of communication masking. The proposed paradigm and mechanisms for measuring levels of communication masking can be applied to different species, contexts, acoustic habitats and ocean noise scenes to estimate the potential impacts of masking at the individual and population levels.

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Section: Examplesmentioning

confidence: 99%

Acoustic masking in marine ecosystems: intuitions, analysis, and implication

Clark¹,

Ellison²,

Southall³

et al. 2009

Mar. Ecol. Prog. Ser.

460

369

View full text Add to dashboard Cite

show abstract

“…The only exception was the 25.6 kHz masker, which was generated and filtered using MATLAB (MathWorks, Natick, MA, USA) and transmitted from the computer through a Roland Quad-Capture USB 2.0 Audio Interface (sampling rate 192 kHz; Roland Corporation US, Los Angeles, CA, USA) and a Reson VP1000 voltage preamplifier (in air only) before reaching the amplifier. Test signals and masking noise were projected from the same speaker to avoid spatial release from masking (Terhune and Turnbull, 1989;Turnbull, 1994;Holt and Schusterman, 2007). For in-air CR determination, the speakers used were the same as for the in-air audiogram.…”

Section: Stimulus Generation and Calibrationmentioning

confidence: 99%

Amphibious hearing in spotted seals (Phoca largha): underwater audiograms, aerial audiograms and critical ratio measurements

Sills

Southall

Reichmuth

2014

Journal of Experimental Biology

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Spotted seals (Phoca largha) inhabit Arctic regions that are facing both rapid climate change and increasing industrialization. While little is known about their sensory capabilities, available knowledge suggests that spotted seals and other ice seals use sound to obtain information from the surrounding environment. To quantitatively assess their auditory capabilities, the hearing of two young spotted seals was tested using a psychophysical paradigm. Absolute detection thresholds for tonal sounds were measured in air and under water over the frequency range of hearing, and critical ratios were determined using octave-band masking noise in both media. The behavioral audiograms show a range of best sensitivity spanning four octaves in air, from approximately 0.6 to 11 kHz. The range of sensitive hearing extends across seven octaves in water, with lowest thresholds between 0.3 and 56 kHz. Critical ratio measurements were similar in air and water and increased monotonically from 12 dB at 0.1 kHz to 30 dB at 25.6 kHz, indicating that the auditory systems of these seals are quite efficient at extracting signals from background noise. This study demonstrates that spotted seals possess sound reception capabilities different from those previously described for ice seals, and more similar to those reported for harbor seals (Phoca vitulina). The results are consistent with the amphibious lifestyle of these seals and their apparent reliance on sound. The hearing data reported herein are the first available for spotted seals and can inform best management practices for this vulnerable species in a changing Arctic.

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“…Psychophysical procedures were similar to those used in Experiment I, with the addition of masking noise on each trial. Masking noise was projected from the same underwater transducer as the signal to prevent spatial release from masking (Turnbull, 1994). The onset of the masking noise coincided with the onset of the light indicating the start of a trial; the noise offset occurred after the end of the 4-s trial interval.…”

Section: Overviewmentioning

confidence: 99%

Auditory sensitivity of seals and sea lions in complex listening scenarios

Cunningham

Southall

Reichmuth

2014

The Journal of the Acoustical Society of America

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Standard audiometric data, such as audiograms and critical ratios, are often used to inform marine mammal noise-exposure criteria. However, these measurements are obtained using simple, artificial stimuli-i.e., pure tones and flat-spectrum noise-while natural sounds typically have more complex structure. In this study, detection thresholds for complex signals were measured in (I) quiet and (II) masked conditions for one California sea lion (Zalophus californianus) and one harbor seal (Phoca vitulina). In Experiment I, detection thresholds in quiet conditions were obtained for complex signals designed to isolate three common features of natural sounds: Frequency modulation, amplitude modulation, and harmonic structure. In Experiment II, detection thresholds were obtained for the same complex signals embedded in two types of masking noise: Synthetic flat-spectrum noise and recorded shipping noise. To evaluate how accurately standard hearing data predict detection of complex sounds, the results of Experiments I and II were compared to predictions based on subject audiograms and critical ratios combined with a basic hearing model. Both subjects exhibited greater-than-predicted sensitivity to harmonic signals in quiet and masked conditions, as well as to frequency-modulated signals in masked conditions. These differences indicate that the complex features of naturally occurring sounds enhance detectability relative to simple stimuli.

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Changes in masked thresholds of a harbour seal (Phoca vitulina) associated with angular separation of signal and noise sources

Cited by 22 publications

References 17 publications

Acoustic masking in marine ecosystems: intuitions, analysis, and implication

Acoustic masking in marine ecosystems: intuitions, analysis, and implication

Amphibious hearing in spotted seals (Phoca largha): underwater audiograms, aerial audiograms and critical ratio measurements

Auditory sensitivity of seals and sea lions in complex listening scenarios

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