Studies on the Aural Reflex. I. Contralateral Remote Masking as an Indicator of Reflex Activity

Abstract

The phenomenon of “contralateral remote masking” is described: the elevation of threshold sensitivity to a low-frequency tone in one ear produced by a high-frequency band of noise in the other. Evidence is presented indicating that this effect is mainly attenuation induced by reflex activation of the stapedius muscle, although probably some central masking is also involved. The strength of the activation (1) increases linearly with sound pressure level of the arousal noise beginning at about 85 db SPL, (2) decreases linearly with frequency level of the noise, and (3) gradually decreases with time (i.e., adapts), reaching an asymptote after about 3 min. Individual differences in reflex activity could not be explained in terms of differences in resting thresholds. The relation of this phenomenon to ipsilateral remote masking and loudness adaptation is studied, and its effect on temporary threshold shift and on loudness judgements at high intensities is discussed.