Abstract:
Ipsilateral click thresholds can improve by approximately 21 dB, with in increase in the click repetition rates from 50/s to 300/s [Rawool, Scand. Audiol. 24 199--205 (1995)] in young normal individuals. This improvement is significantly reduced in older individuals [Rawool, J Gerontol. Biol. Sci. (in press)]. The current investigation was designed to evaluate the effect of age-related hearing impairment on the rate-induced improvement in the acoustic reflex thresholds. Ipsilateral acoustic reflex thresholds were obtained from 60 older ears in the age range of 50 to 74 years. The subjects were divided into four groups: (I) Normal. Hearing within normal limits (20 dB). (II) Mid high-frequency impairment. Hearing within normal limits up to 2 kHz, and an average impairment of 17.5 to 25 dB at 3, 4, 6, and 8 kHz. (III) Moderate high-frequency impairment. Hearing within normal limits up to 2 kHz and an average impairment of 35 to 61 dB at 3, 4, 6, and 8 kHz. (IV) Flat hearing impairment. Hearing impairment across the test frequencies. Ipsilateral acoustic reflex thresholds were obtained from the left and/or right ear by presenting clicks at the repetition rates of 50, 100, 150, 200, and 300 clicks/s. No significant differences were apparent in the rate-induced improvement (11 to 14 dB) in the acoustic reflex thresholds across the four groups.