Remote masking in noise-exposed chinchillas.

Remote masking (RM), the phenomenon whereby an intense high-frequency masker elevates thresholds for low-frequency signals, has been shown to be sensitive to various types of hearing loss in humans and to temporary threshold shifts in chinchillas. In this experiment, RM was evaluated in chinchillas with permanent threshold shift (PTS). Thresholds for 0.5 and 1 kHz tones were measured in quiet and in the presence of an 88 dB SPL narrow band noise centered at 3 kHz in the animals exposed for 30 h to impact noise at 125 dB SPL as intensity. The results show that RM values are significantly lower in chinchillas with PTS than in normal hearing chinchillas.