Todd Schneider
Donald G. Jamieson
Hear. Health Care Res. Unit, Univ. of Western Ontario, London, ON N6G 1H1, Canada
An automated dual-channel maximum-length sequence (MLS) test system for the electroacoustic characterization of hearing aids has been developed. This test system applies a speech-shaped MLS acoustically to a hearing aid and measures the electro-acoustic frequency response. This method provides results that compare favorably to those obtained using the method employed by Kates [J. M. Kates, J. Rehab. Res. Develop. 27, 255--278 (1990)] and the ANSI standard method [ANSI S3.42 (1992)]. Test results show that MLS-based testing is significantly faster than noise-based testing. Two signal-biased MLS-based testing methods have also been developed. These methods apply a bias signal to force the hearing aid into a mode of operation where the frequency response, with adaptive or subtractive bias signal cancellation, is measured using a low-level, speech-shaped MLS. This method has proved valuable for the characterization of automatic signal processing hearing aids. [Work supported by ORTC and OMH.]