Comparison of a two-branch and a four-branch artificial ear

Abstract

A two-branch artificial ear was compared with two four-branch artificial ears (Zwislocki couplers). Overall results from the two coupler types were very similar. The equivalent volumes of the couplers were evaluated by comparing the levels developed in these couplers with the level developed by the same signal in a 2-cc cavity. From 100 to 5000 Hz the equivalent volume of the two-branch coupler was slightly less than that of the four-branch couplers, the difference never exceeding 0.1 cc. The acoustic damping provided by the couplers was compared by measuring the amplitude of reactance resonances observed when the couplers constituted the volume of the resonator (a situation analogous to the acoustic system operating when vented earmolds are used). In the 400–700-Hz range, resonances developed in the two-branch coupler were 2–3 dB less damped than the analogous four-branch coupler resonances. In the 2–3-kHz range the damping of the couplers was approximately equal. This evidence suggests that the two-branch coupler provides less damping of typical vent related resonances than does the real ear. [Work supported by NIH.]