Long-term evidence of noise-induced permanent threshold shift in a harbor seal (Phoca vitulina)
Abstract
In psychophysical studies of noise-induced hearing loss with marine mammals, exposure conditions are often titrated from levels of no effect to those that induce significant but recoverable loss of auditory sensitivity [temporary threshold shift (TTS)]. To examine TTS from mid-frequency noise, a harbor seal was exposed to a 4.1-kHz underwater tone that was incrementally increased in sound pressure level (SPL) and duration. The seal's hearing was evaluated at the exposure frequency and one-half octave higher (5.8 kHz) to identify the noise parameters associated with TTS onset. No reliable TTS was measured with increasing sound exposure level until the second exposure to a 60-s fatiguing tone of 181 dB re 1 μPa SPL (sound exposure level 199 dB re 1 μPa2s), after which an unexpectedly large threshold shift (>47 dB) was observed. While hearing at 4.1 kHz recovered within 48 h, there was a permanent threshold shift of at least 8 dB at 5.8 kHz. This hearing loss was evident for more than ten years. Furthermore, a residual threshold shift of 11 dB was detected one octave above the tonal exposure, at 8.2 kHz. This hearing loss persisted for more than two years prior to full recovery.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Oct 01, 2019
- Source ID
- 10.1121/1.5129379
Entities
People
- Asila Ghoul
- Colleen Reichmuth
- Jason Mulsow
- Jillian M. Sills
Organizations
- National Marine Mammal Foundation
- Office of Naval Research
- University of California, Santa Cruz