Effects of stimulus duration and stimulus off time on the auditory and acoustic reflex thresholds

Ipsilateral acoustic reflex thresholds at varying click rates in humans

The effects of the click repetition rates on the ipsilateral acoustic reflex thresholds were investigated in 17 normal female subjects (total 34 ears) within the age-range of 20 to 26 years. The acoustic reflexes were elicited in response to condensation clicks (100 microseconds duration) at repetition rates of 50, 100, 150, 200, 250 and 300/sec. The probe tone frequency was 226 Hz and the intensity was 85dB SPL. The thresholds improved significantly with increase in the repetition rates. The mean threshold advantage was 11.2dB with an increase in the rate from 50 to 100/sec, it was 7.8dB when the rate was increased from 100 to 200/sec and was further reduced to 2.6dB when the rate was increased from 200 to 300/sec. These findings are discussed with reference to the temporal and the spatial summation and facilitation. Possible clinical implications of the findings are presented.