Hearing aid microphone location effects on speech discrimination in noise

The interaction of the head with a sound impinging upon it has a direct effect on the sound as it is seen at the port of the hearing aid microphone. While other investigators have evaluated this effect in terms of changes in the frequency response of the hearing aid, this investigation sought to evaluate the significance of the effect in terms of the intelligibility of speech presented in a noisy background. The three typical locations of a hearing aid microphone were simulated with a high-fidelity probe-tube microphone placed around the right ear of KEMAR. The locations were: over the ear, behind the ear, and in the ear. An earmold was kept in the ear at all times. Speech and noise were presented to the microphone and recorded on tape for presentation to normally hearing subjects. The results indicated that so long as the hearing aid microphone is located on the head, around the ear, no one location is better than any other for speech intelligibility.