Contralateral Threshold Shift and Reduction in Temporary Threshold Shift as Indices of Acoustic Reflex Action

The purpose of the experiment was twofold: to compare the effectiveness of narrow band noise and a train of clicks in eliciting the middle ear acoustic reflex and to correlate two methods of estimating amount of reflex activation. One method involved measurement of increase in threshold in the contralateral ear; the other, measurement of reduction of TTS produced by a series of gun shots. Sixteen subjects were employed. Shifts produced by the clicks and noise were of the same order of magnitude (after correction for the direct masking effect by the clicks), but there was considerable reflex adaptation to the noise and none for the clicks. Correlations between contralateral threshold shift and reduction of TTS were small and not significant.