Study of noise-induced hearing loss by distortion product otoacoustic emissions

Background and objective: 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). Methods: 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). Findings: 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). Conclusion: 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