Spectral changes produced by earphone-cushion reproduction of hearing aid-processed signals.

This investigation was conducted to assess the extent to which hearing aid-processed signals present an acoustic signal to the subject which has a frequency response equivalent to that which the hearing aid itself would have provided. The frequency response of a hearing aid receiver which was coupled directly to the ear canal ("aided" condition) was compared with the frequency response of the same receiver when its output was recorded on magnetic tape and then presented to the subject via a TDH-49 earphone ("pseudoaided" condition). Results indicated that when the earphone was mounted in an MX-41/AR cushion or either of two circumaural cushions, the spectrum of the sound arriving at the subject's eardrum in the pseudoaided condition was substantially different from the spectrum delivered in the aided condition.