Acoustic Trauma after Double Exposure in Mammals

Abstract

Intense pure tones (120-127 dB SPL) of 4-25 kHz have previously been used to produce localized damage to the cochlea in the various mammalian species. Minimum exposure durations were used to obtain a restricted area of damage, but this varied according to the frequencies used. This study has now been extended to include a lower frequency, so that two widely separated frequencies (2 and 20 kHz) can be used on the same animal. A time interval of 3-4 weeks was generally left between the first and seconds exposures, so that destruction of the sensory cells due to the first exposure would be almost complete before the second exposure. The two frequencies were presented in both orders, i.e. lower frequency first, followed by the higher frequency or vice versa. The results indicate that after double exposure neither the location nor the extent of the damaged area of sensory cells is changed from that obtained by single exposure to either frequency

Key Words:

• Acoustic trauma
• Double exposures to pure tones
• Guinea pig