Effect of sound conditioning on click auditory brainstem response threshold shifts in guinea pigs

Sound conditioning is exposure to a non-traumatic، moderate level of sound which increases inner ear resistance against further severe noise. In this study، we aimed to survey the effect of sound conditioning on auditory brainstem response (ABR) threshold shifts using click stimulus، and the effect of the frequency of conditioning on hearing protection. Fifteen guinea pigs were randomly divided into 3 groups. Two conditioned groups were exposed to 1 kHz، and 4 kHz octave band noise at 85 dB SPL، 6 hours per day for 5 days، respectively. On the sixth day، the animals were exposed to 4 kHz octave band noise at 105 dB SPL، for 4 hours. The control group was exposed to intense noise، 4 kHz at 105 Db SPL for 4 hours (without conditioning). After exposure، ABR thresholds using click were recorded an hour، and 7 days after noise exposure. The results of the ABR with click stimulus showed less thresold shifts in conditioned groups than control (p≤0. 001). Comparison of the results of conditioned groups، showed less threshold shift by 4 kHz conditioning، however، this difference was not statistically significant (p>0. 05). Electrophysiological data of our study showed that sound conditioning has a protective effect against subsequent intensive noise exposure، and the frequency of conditioning does not have significant effect on ABR threshold shifts when using click stimulus.