Phenomenologic aspects of the acoustic reflex following noise exposure

Thirty-seven normal hearing subjects were exposed to broadband noise for 2 hours at 90 dB (Lp). Measures of behavioral thresholds and acoustic reflex activity were completed prior to and following the noise exposure. As expected, temporary threshold shift was obtained at several different frequencies (1.0-6.0 kHz). In addition, reflex threshold shift occurred for all pure-tone elicitors under evaluation (0.5 to 4.0 kHz). The observed shift in acoustic reflex threshold at 0.5 kHz without a concomitant change in behavioral sensitivity reveals the limitation of utilizing behavioral threshold testing as the sole measure of cochlear disruption. Changes in acoustic reflex onset latency and magnitude were not observed after compensating for shifts in acoustic reflex threshold.