Quantification of the acoustic reflex latency parameters in humans

Abstract

This study defined and quantified reflex latencies in humans with normal auditory function and examined stimulus rise time in relation to changes in the acoustic reflex latency parameters. A carefully controlled and monitored 2000-Hz acoustic signal with four different rise times was presented 10 dB above each subject's clinical reflex threshold. The acoustic reflex response was photographed from an oscilloscope and read from a microfilm reader. The time course of the reflex responses was measured. Mean values for the latency parameters, maximum impedance changes, and acoustic reflex rise times were determined. It is proposed that latency be defined from the point of impedance change rather than from signal onset. This definition provides a less variable latency measure. Latency varied with intensity of the acoustic stimulus within the dynamic range of the reflex. It was not affected by other variables such as signal rise time, signal duration, or time constants of the electroacoustic impedance bridge. Latency of the acoustic reflex varied as a function of stimulus rise time and was energy dependent. [Work supported by HEW.]