Author:

Keywords:

Science & Technology, Technology, Life Sciences & Biomedicine, Acoustics, Audiology & Speech-Language Pathology, OCTAVE-BAND NOISE, DOLPHINS TURSIOPS-TRUNCATUS, SINGLE UNDERWATER IMPULSES, BEHAVIORAL-RESPONSES, TONAL SIGNALS, SHIFT, EXPOSURE, DURATION, LEVEL, KHZ, Acoustic Stimulation, Animals, Auditory Fatigue, Behavior, Animal, Ecosystem, Environmental Exposure, Male, Noise, Oceans and Seas, Phocoena, Psychoacoustics, Risk Assessment, Sound Spectrography, Swimming, Time Factors

Abstract:

Harbor porpoises may suffer hearing loss when exposed to intense sounds. After exposure to playbacks of broadband pile driving sounds for 60 min, the temporary hearing threshold shift (TTS) of a porpoise was quantified at 0.5, 1, 2, 4, 8, 16, 32, 63, and 125 kHz with a psychoacoustic technique. Details of the pile driving sounds were as follows: pulse duration 124 ms, rate 2760 strikes/h, inter-pulse interval 1.3 s, average received single strike unweighted sound exposure level (SEL) 146 dB re 1 μPa(2) s (cumulative SEL: 180 dB re 1 μPa(2) s). Statistically significant TTS only occurred at 4 and 8 kHz; mean TTS (1-4 min. after sound exposure stopped) was 2.3 dB at 4 kHz, and 3.6 dB at 8 kHz; recovery occurred within 48 min. This study shows that exposure to multiple impulsive sounds with most of their energy in the low frequencies can cause reduced hearing at higher frequencies in harbor porpoises. The porpoise's hearing threshold for the frequency in the range of its echolocation signals was not affected by the pile driving playback sounds.