Study of Noise-Induced Hearing Loss by Distortion Product Otoacoustic Emissions

Noise-induced hearing loss remains as the most common problem in industrial societies. This research was conducted to study noise-induced hearing loss by distortion-product otoacoustic emissions (DPOAEs). This study was carried out on 12 male New Zealand White rabbits including control (exposed to noise) and experimental (exposed to 95 dBA SPL white noise at 500-8000 Hz for 8 hours per day during 5 consecutive days). DPOAEs were measured and compared in days zero (before exposure as baseline), eighth (experimental: an hour after latest exposure to noise for Temporary Threshold Shifts: TTS), tenth (experimental: 48 hours after latest exposure to noise for Permanent Threshold Shifts: PTSs). The most and the least values of TTSs, PTSs and DPOAEs amplitude in noise group were correspond to frequencies of 5888.50 Hz and 588.00 Hz, respectively (p<0.05). There was a significant difference between TTSs, PTSs and DPOAEs amplitude at different frequencies in right and left ear of noise group (p<0.05). This difference was related to frequency 5888.5 Hz in each of right and left ear of noise group compared to other frequencies in same ear (p<0.05). There were not any significant difference between TTSs, PTSs and DPOAEs amplitude of right and left ear of noise group at different frequencies (p>0.05). Excessive noise can cause TTSs and noise-induced PTSs and decreased DPOAEs amplitudes. Therefore, DPOAEs can be attributed as a useful tool for study of noise-induced hearing loss.