Temporary threshold shifts and recovery following noise exposure in the Atlantic bottlenosed dolphin (<i>Tursiops truncatus</i>)

SUMMARYTemporary threshold shift (TTS) after loud noise exposure was investigated in a male and a female beluga whale (Delphinapterus leucas). The thresholds were evaluated using the evoked-potential technique, which allowed for threshold tracing with a resolution of ~1min. The fatiguing noise had a 0.5octave bandwidth, with center frequencies ranging from 11.2 to 90kHz, a level of 165dBre.1μPa and exposure durations from 1 to 30min. The effects of the noise were tested at probe frequencies ranging from -0.5 to +1.5octaves relative to the noise center frequency. The effect was estimated in terms of both immediate (1.5min) postexposure TTS and recovery duration. The highest TTS with the longest recovery duration was produced by noises of lower frequencies (11.2 and 22.5kHz) and appeared at a test frequency of +0.5octave. At higher noise frequencies (45 and 90kHz), the TTS decreased. The TTS effect gradually increased with prolonged exposures ranging from 1 to 30min. There was a considerable TTS difference between the two subjects.

Section: Fatiguing Sound Level and Durationmentioning

confidence: 99%

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

Supin

Рожнов

et al. 2013

“…In a study by Nachtigall et al (Nachtigall et al, 2003), a 50 min bandpass (4 to 11 kHz) noise exposure of 179 dB re. 1 μPa (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…The sensitive and wide-ranging hearing of toothed whales and dolphins, which is used for both passive hearing and echolocation (Au, 1993;Nachtigall et al, 2000), may be particularly susceptible to damage by intensive noise. The impact of noise on this auditory system is known as the permanent or temporary threshold shift (PTS or TTS, respectively), which is a reduction in sensitivity.…”

Section: Introductionmentioning

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

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.

“…Unfortunately, we do not know the noise exposure history of the present subject, but based on the location of the animal's stranding and its home range observed between 1996 and 2010, it is possible that the older dolphin had been exposed to chronic environmental noise from boating and shipping and other natural and anthropogenic sources of noise. However, controlled experiments with odontocetes have shown that high levels of exposure are needed to induce temporary threshold shifts (Finneran et al, 2002;Finneran et al, 2005a;Nachtigall et al, 2003;Mooney et al, 2009). During the post-stranding treatment and rehabilitation, the older dolphin was not given ototoxic medicines such as aminoglycosidic antibiotics, which might damage the hair cells of the cochlea and result in dolphin hearing loss (Finneran et al, 2005b).…”

Section: Discussionmentioning

confidence: 99%

Possible age-related hearing loss (presbycusis) and corresponding change in echolocation parameters in a stranded Indo-Pacific humpback dolphin

Wang

et al. 2013

SUMMARYThe hearing and echolocation clicks of a stranded Indo-Pacific humpback dolphin (Sousa chinensis) in Zhuhai, China, were studied. This animal had been repeatedly observed in the wild before it was stranded and its age was estimated to be ~40years. The animal's hearing was measured using a non-invasive auditory evoked potential (AEP) method. Echolocation clicks produced by the dolphin were recorded when the animal was freely swimming in a 7.5m (width)×22m (length)×4.8m (structural depth) pool with a water depth of ~2.5m. The hearing and echolocation clicks of the studied dolphin were compared with those of a conspecific younger individual, ~13years of age. The results suggested that the cut-off frequency of the high-frequency hearing of the studied dolphin was ~30-40kHz lower than that of the younger individual. The peak and centre frequencies of the clicks produced by the older dolphin were ~16kHz lower than those of the clicks produced by the younger animal. Considering that the older dolphin was ~40years old, its lower high-frequency hearing range with lower click peak and centre frequencies could probably be explained by age-related hearing loss (presbycusis).