Intensity-time tradeoff for constant hearing loss with high sound levels.

The tradeoff relation between exposure intensity and duration for constant hearing loss was investigated in two series of experiments using Mongolian gerbils. The gerbils were exposed to a 1/3 octave band of noise at 2.5 kHz. In the first series animals were exposed to 120 dB SPL for 1 h, to 126 dB SPL for 15 min, and to 126 dB SPL for 3.75 min. In the second series, shorter durations were used: 120 dB SPL for 15 min, 126 dB SPL for 3.75 min, and 126 dB SPL for 56 s. The hearing thresholds were determined behaviorally immediately before exposure and 6 weeks after exposure. The results suggest that the intensity-time tradeoff for the investigated intensity interval is between 1.5 and 3 dB per halving of the duration.