Localization through hearing aids

Abstract

Stereophonic signal presentation was used to assess localization abilities through ear‐level hearing aids. The experiment was performed in a small sound insulated room. Two loudspeakers were 2 m away from the subject forming ±30° azimuths. The subject was sitting on a chair with a head rest. He faced two strings 30 cm apart hanging on the midline between the loudspeakers and lined them up visually. Two additional strings are marked ±15° azimuths. The subject varied the position of a phantom source by controlling the relative level of signal (uninterrupted flow of speech) by means of a potentiometer. Four conditions were tested: unaided, aided with identical gains of the hearing aids and aided with the gains 10 dB different (right or left ear more amplified). Each subject made 10 adjustments for −15, 0, and +15° azimuth. Each subject was tested two times. Seven subjects with normal hearing produced unaided data similar to reported previously [(Theile and Plenge, J. Aud. Eng. Soc. 25, 196–200 (1977)]. The results for identical gains were similar to unaided results. The asymmetrical conditions produced images shifted toward the ear getting more amplification. The average shift was +4.6 and −2.6 dB for left and right ear more amplified, respectively. However the amount of shift varied among subjects. The method might have potential for testing localization abilities of hearing‐impaired subjects. [Supported by NIH NISND grant.]