Time and frequency metrics related to auditory masking of a 10 kHz tone in bottlenose dolphins (Tursiops truncatus)

Abstract

Metrics related to the frequency spectrum of noise (e.g., critical ratios) are often used to describe and predict auditory masking. In this study, detection thresholds for a 10 kHz tone were measured in the presence of anthropogenic, natural, and synthesized noise. Time-domain and frequency-domain metrics were calculated for the different noise types, and regression models were used to determine the relationship between noise metrics and masked tonal thresholds. Statistical models suggested that detection thresholds, masked by a variety of noise types at a variety of noise levels, can be explained with metrics related to the spectral density of noise and the degree to which amplitude modulation is correlated across frequency regions of the noise. The results demonstrate the need to include time-domain metrics when describing and predicting auditory masking.

Human auditory discrimination of bottlenose dolphin signature whistles masked by noise: Investigating perceptual strategies for anthropogenic noise pollution

“…Unsurprisingly, masking noise can impair dolphins' abilities to echolocate accurately, which could impact their ability to forage. One study (Lemonds, Au, Vlachos, & Nachtigal, 2012) which examined a bottlenose dolphin's masked hearing thresholds of a pure tone, found similar masking patterns to the aforementioned body of research (Au et al, 1988;Au & Penner, 1981;Branstetter et al, 2016a;Branstetter et al, 2013a) on masking and echolocation. Branstetter and colleagues (2016a) studied the effects of several types of natural and artificial noise sources on dolphin detection of various natural and artificial dolphin vocalizations: one non-signature whistle, one burst pulse, echolocation clicks, a 10 kHz tone, and four artificial, whistle-like sounds.…”

“…These processes are difficult to account for with current knowledge of dolphin auditory perception, communication, and cognitive abilities. However, the large body of literature on acoustic masking in dolphins would seem to indicate that these processes are fairly similar in both humans and dolphins (Au et al, 1988;Au & Penner, 1981;Branstetter et al, 2016a;Branstetter et al, 2013a;Lemonds, Au, Vlachos, & Nachtigal, 2012). A follow-up study on dolphin perception of the same stimuli could reveal the extent to which this study's findings generalize to dolphins.…”

“…The extent to which masking noise might impair a dolphin's ability to echolocate has been studied in great detail with animals in human care (e.g., Au et al, 1988;Au & Penner, 1981;Branstetter et al, 2016a;Branstetter, Trickey, Aihara, Finneran, & Liberman, 2013a), revealing thresholds at which sounds affect dolphins' ability to detect or discriminate among objects using echolocation. In general, this research suggests that, like in humans, the effects of masking noise vary with both the frequency and amplitude of both the noise and the signal.…”

Mechanisms of auditory masking in marine mammals

“…Although a mechanistic model has not been applied to describe and predict auditory masking in marine mammals with different noise types, Branstetter et al ( 2013b ) produced a linear model to describe masking patterns with 12 different noise types and detection thresholds from three different bottlenose dolphins. Predictor variables were noise statistics, and they were divided into three categories: (1) waveform metrics (e.g., RMS and kurtosis), (2) frequency spectrum metrics (e.g., spectral density), and (3) temporal envelope metrics (e.g., envelope kurtosis, comodulation index).…”

Spatial and Temporal Variation in the Acoustic Habitat of Bottlenose Dolphins (Tursiops aduncus) within a Highly Urbanized Estuary

“…The nth percentile gives the level that was exceeded n% of the time. frequency (Branstetter et al, 2013). It is the different temporal structures and comodulation degrees that will likely reduce the risk of acoustic masking by snapping shrimp over that of vessels (Erbe, 2008;Erbe et al, 2016b).…”