Internal circuit noise of hearing aids and speech intelligibility

The circuit noise generated internally by various components of a hearing aid is influenced mostly by circuit gain and frequency response. The measurement of this variable and its effect, if any, on the listener's ability to unders-and monosyllabic words through a hearing-aid system was investigated. The overall circuit noise of 10 behind-the-ear hearing aids of different brands with comparable gain and frequency response was measured. Based on these measurements, a low-noise and a high-noise hearing aid were selected as the test aids. The internal circuit noise of each test aid was then measured automatically by utilizing a 1/3-octave-band tracking filter. Monosyllabic words were recorded through the test aids at two gain settings. The prerecorded test tapes were presented to 32 normal-hearing listeners. Findings indicate that different amounts of circuit noise generated internally by a hearing aid do exist among various aids. However, the noise generated by the hearing aids used in this study does not affect significantly the intelligibility of monosyllabic words.