Characterization of acoustic reflex latency in normal-hearing subjects.

Acoustic reflex latency (ARL) has been suggested as an indicator in otoneurological diagnosis. However, limited normative data are available. Conflicting evidence exists regarding the effect of stimulus parameters such as frequency on ARL. In addition, there has been little research investigating the effects of ipsilateral and contralateral stimulation on ARL. In view of these problems, ARL was measured in 30 normal-hearing subjects using 500, 1000, 2000, 4000 Hz tones, low-pass noise, high-pass noise, broadband noise and clicks as activating stimuli. Six parameters of ARL: 10%-on latency, 90%-on latency, 10%-off latency, 90%-off latency, rise time and fall time, were recorded using computerized equipment and analyzed in correlation to the activating frequency and intensity. This study indicated that 500 Hz, 1000 Hz tones, and band noise were more effective in eliciting measurable ARL, whereas 4000 Hz tone and click produced a low percentage of measurable ARL. ARL was shown to increase as the stimulus frequency increased and stimulus intensity decreased. No statistically significant differences were found between the ipsilateral ARL and contralateral ARL.