Filter effect of earmold venting: comparison of electroacoustic and psychoacoustic methods of evaluation

The filter effect of venting an earmold was evaluated by measuring the coupler-acoustic and threshold responses to open versus closed earmolds. In the coupler-acoustic technique the effect of venting was determined by measuring the output of the experimental earmolds seated on a modified 2-cc coupler with a specified signal impressed upon the earphone. The real ear threshold technique called for the determination of threshold by five listeners for the same earphone-earmold system. The data indicated that the difference between the coupler and threshold measures were of the same order of magnitude as the difference seen by other investigators reporting coupler and real ear-probe tube microphone measures. It was concluded that the threshold technique provides the same general description of the effects of venting an earmold as does the probe tube technique and should thus provide a useful method for determination of the filter effects produced by the venting of an earmold.