Hearing threshold shifts and recovery after noise exposure in beluga whales, Delphinapterus leucas

Self Cite

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 22.5 kHz and a sound pressure level of 165 dB re. 1 μPa rms, hearing thresholds before the loud sound increased relative to the baseline. The threshold increased up to 15 dB. In order to further investigate whether the observed threshold increase was due to conditioning, the dependence of the effect on warning duration and inter-trial interval was investigated. The duration of the warning substantially influenced the effect. Shorter warnings resulted in deeper suppression of responses and higher threshold increases than longer warnings. In contrast, the effect was nearly independent of the duration of the inter-trial interval, i.e. it was independent of the delay from the loud sound to the test/warning sound in the subsequent trial. These data are considered as evidence that the observed hearing threshold increases were not a result of the unconditioned effect of the loud sound and were instead a manifestation of a conditioned dampening of hearing when the bottlenose dolphin anticipated the quick appearance of a loud sound in the same way as previously demonstrated in the false killer whale.

Section: Conditioned or Non-conditioned Effect?mentioning

confidence: 99%

Conditioned hearing sensitivity reduction in a bottlenose dolphin (Tursiops truncatus)

Nachtigall

Supin

2014

Self Cite

“…Combined with the 6 dB variability sometimes seen over the course of pre-exposure threshold determination, these data suggest that variability of 3-6 dB is within the normal range of performance of bats in these experiments. In marine mammals, Finneran and Schlundt (2013) and Popov et al (2013) both adopted a criterion of ±5 dB to monitor threshold stability, while in laboratory-bred rats (Rattus norvegicus), Heffner et al (2008) used a criterion of 3-5 dB to indicate threshold stability and good correspondence between behavioral and electrophysiological measures of hearing sensitivity. The variability in our threshold measurements is consistent with these criteria.…”

Section: Reliability Of Measurements Of Hearing Sensitivitymentioning

confidence: 99%

“…Cumulative short duration exposures or long duration exposures of days to weeks produce permanent threshold shifts from which recovery does not fully occur (Clark, 1991). These impairments have been documented in many vertebrate species, including fishes (Amoser and Ladich, 2003;Smith et al, 2004), birds (Ryals et al, 1999), rodents (Ryan and Bone, 1978;Boettcher, 1993;Heffner et al, 2008), marine mammals (Popov et al, 2013;Finneran, 2015) and humans (Ward et al, 1958;Mills et al, 1981). In spite of species and individual differences in the most effective acoustic parameters for producing TTS, these animals all demonstrate some hearing losses under some exposure conditions.…”

Section: Introductionmentioning

confidence: 99%

Broadband noise exposure does not affect hearing sensitivity in big brown bats (Eptesicus fuscus)

Simmons

Hom

Warnecke

2016

In many vertebrates, exposure to intense sounds under certain stimulus conditions can induce temporary threshold shifts that reduce hearing sensitivity. Susceptibility to these hearing losses may reflect the relatively quiet environments in which most of these species have evolved. Echolocating big brown bats (Eptesicus fuscus) live in extremely intense acoustic environments in which they navigate and forage successfully, both alone and in company with other bats. We hypothesized that bats may have evolved a mechanism to minimize noise-induced hearing losses that otherwise could impair natural echolocation behaviors. The hearing sensitivity of seven big brown bats was measured in active echolocation and passive hearing tasks, before and after exposure to broadband noise spanning their audiometric range (10-100 kHz, 116 dB SPL re. 20 µPa rms, 1 h duration; sound exposure level 152 dB). Detection thresholds measured 20 min, 2 h or 24 h after exposure did not vary significantly from pre-exposure thresholds or from thresholds in control (sham exposure) conditions. These results suggest that big brown bats may be less susceptible to temporary threshold shifts than are other terrestrial mammals after exposure to similarly intense broadband sounds. These experiments provide fertile ground for future research on possible mechanisms employed by echolocating bats to minimize hearing losses while orienting effectively in noisy biological soundscapes.

“…sound pressure. The frequencies of the test and fatiguing sounds were chosen because a previous investigation revealed this combination to be very effective at producing TTS in belugas (Popov et al, 2013).…”

Section: Test and Fatiguing Soundsmentioning

confidence: 99%

The limits of applicability of the sound exposure level (SEL) metric to temporal threshold shifts (TTS) in beluga whales, Delphinapterus leucas

Попов

Supin

Рожнов

et al. 2014

Self Cite

The influence of fatiguing sound level and duration on post-exposure temporary threshold shift (TTS) was investigated in two beluga whales (Delphinapterus leucas). The fatiguing sound was half-octave noise with a center frequency of 22.5 kHz. TTS was measured at a test frequency of 32 kHz. Thresholds were measured by recording rhythmic evoked potentials (the envelope following response) to a test series of short (eight cycles) tone pips with a pip rate of 1000 s −1 . TTS increased approximately proportionally to the dB measure of both sound pressure (sound pressure level, SPL) and duration of the fatiguing noise, as a product of these two variables. In particular, when the noise parameters varied in a manner that maintained the product of squared sound pressure and time (sound exposure level, SEL, which is equivalent to the overall noise energy) at a constant level, TTS was not constant. Keeping SEL constant, the highest TTS appeared at an intermediate ratio of SPL to sound duration and decreased at both higher and lower ratios. Multiplication (SPL multiplied by log duration) better described the experimental data than an equal-energy (equal SEL) model. The use of SEL as a sole universal metric may result in an implausible assessment of the impact of a fatiguing sound on hearing thresholds in odontocetes, including under-evaluation of potential risks.