Influence of acoustic reflex on acquisition of temporary threshold shift from short duration noise bursts.

The purpose of this study was to examine the relationship between the acoustic reflex elicited by short duration noise bursts and the resultant temporary threshold shift. Acoustic reflex responses were monitored during the presentation of fatiguing stimuli consisting of interrupted and continuously presented octave noise bands (500--1000 and 1500--3000 Hz) presented at 98 dB sound pressure level. For interrupted stimuli, burst duration was maintained at 100 msec while five different off times ranging from 50 to 450 msec (in 100-msec steps) were used. Exposure duration was varied to equate total energy received in each off-time condition. Noise exposures having shorter off times produced significantly more reflex activity than did exposures with longer off times. Greater impedance changes were elicited by the high band noise than by the low band noise exposure. Although the high band noise tended to produce greater reflex activity it also produced significantly more temporary threshold shift. Differences in the amount of temporary threshold shift produced by the two noise bands could not be attributed to the effects of reflex contraction.