Abstract:
Ipsilateral click thresholds obtained with a 226-Hz probe tone can improve by approximately 21 dB, with an increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24, 199--205 (1995)]. This investigation was designed to evaluate the effect of higher probe frequencies on the click-evoked acoustic reflex thresholds and on the rate-induced improvement in the acoustic reflex thresholds. Twelve female and six male subjects with normal hearing participated in the study. Ipsilateral acoustic reflex thresholds were obtained from the left ear of each subject by presenting clicks at the repetition rates of 60, 120, 180, 240, and 300 clicks/s. The results were obtained for three probe tone frequencies: 226, 678, and 1000 Hz. All the subjects showed a decrease in admittance for the 226-Hz probe and an increase in the admittance for the 1000-Hz probe. For the 678-Hz probe, some subjects showed an increase in admittance and others showed a decrease in admittance. The acoustic reflex thresholds were significantly elevated for the 678-Hz probe tone. The rate-induced improvement in acoustic reflex thresholds for each subject was calculated as the difference between the minimum and maximum acoustic reflex thresholds. This improvement (13 to 17 dB) was not significantly different for the three probe tones.