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

Abstract

Temporary 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 0.5octave bandwidth, with center frequencies ranging from 11.2 to 90 kHz, a level of 165dBre.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 +1.5octaves relative to the noise center frequency. The effect was estimated in terms of both immediate (1.5min) postexposure TTS and recovery duration. The highest TTS with the longest recovery duration was produced by noises of lower frequencies (11.2 and 22.5kHz) and appeared at a test frequency of +0.5octave. At higher noise frequencies (45 and 90kHz), 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. © 2013. Published by The Company of Biologists Ltd.