Acoustic Impedance Measured on Ears with Normal and Diphasic Impedance Changes

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Abstract
The aim of the present study was to find out if a diphasic decrease in impedance, elicited by middle-ear muscle activity and recorded in a normal-hearing ear, is correlated with a high static impedance. Therefore, the static acoustic impedance (compliance and resistance) was measured in 18 normal-hearing ears with normal impedance changes, and the values were compared with those obtained in 13 normal-hearing ears showing diphasic impedance changes. In ears with diphasic impedance changes, the compliance (expressed in cm3 of equivalent volume of air) measured in the frequency range 125–750 Hz was found to be substantially decreased, compared with normal ears. In addition, the resistance for the frequencies 1000 and 1500 Hz was decreased relative to normal ears. These findings are suggested to indicate otosclerosis. Therefore a diphasic decrease in acoustic impedance elicited by middle-ear muscle activity in the normal-hearing ear seems to indicate an early stage of otosclerosis.

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