Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 50 10 2012 10 15 664 669 EN Akram Pourbakht Rehabilitation Research Center, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran. Azadeh Imani Department of Audiology, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran. 2015 09 28 We compared the extent of temporary threshold shift (TTS) and hair cell loss following high level 4 kHz noise exposure with those preconditioned with moderate level 1 and 4 kHz octave band noise. Fifteen Male albino guinea pigs (300- 350 g in weight) were randomly allocated into three groups: those exposed to 4 kHz octave band noise at 102 dB SPL (group 1, n=5); those conditioned with 1 kHz octave band noise at 85 dB SPL, 6 hours per day for 5 days, then exposed to noise (group 2, n=5); those conditioned with 4 kHz octave band noise at 85 dB SPL, then exposed to noise (group 3, n=5). An hour and one week after noise exposure, threshold shifts were evaluated by auditory-evoked brainstem response (ABR) and then animals were euthanized for histological evaluation. We found that TTS and cochlear damage caused by noise exposure were significantly reduced by 1 kHz and 4 kHz conditioning (P<0.001). We also showed that 4 kHz protocol attenuates noise- induced TTS but no significant TTS reduction occurred by 1 kHz conditioning. Both protocol protected noise-induced cochlear damage. We concluded that lower tone conditioning could not protect against higher tone temporary noise-induced hearing loss, thus conditioning is a local acting and frequency-dependent phenomenon. https://acta.tums.ac.ir/index.php/acta/article/view/3970 https://acta.tums.ac.ir/index.php/acta/article/download/3970/3945