Asymptotic noise-induced temporary threshold shift in chinchilla measured by the auditory evoked response.

Monaural chinchillas were exposed to octave band (4 kHz center frequency) noise at 80 dB SPL for 96 h. Auditory threshold at frequencies of 1, 2, 4, and 8 kHz was estimated by the auditory evoked response (AER) technique prior to noise exposure, and on a fixed schedule, both during exposure and following removal from the noise. Results were analyzed in terms of both threshold and threshold shift. Results indicate that the AER is adequate measure of asymptotic noise-induced temporary threshold shift. Advantages of the use of AER as opposed to behavioral means of threshold determination are discussed. Threshold during this long-term noise exposure was found to be determined by the spectral and intensity components of the noise independent of pre-exposure threshold. Implications for future research in long-term noise exposure are discussed.