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Differences Between Speech-Shaped Test Stimuli in Analyzing Systems and the Effect on Measured Hearing Aid Gain

Keidser, Gitte; Dillon, Harvey; Convery, Elizabeth; O'Brien, Anna

doi: 10.1097/AUD.0b013e3181ce695d
Brief Report

Objectives: To determine the effect of spectral differences between stimuli used for verification of hearing aid gain in nonlinear devices.

Design: The spectra of nine stimuli from five analyzing systems were obtained.

Results: Most stimuli closely duplicated one of two well-specified spectra. The difference between these two input spectra resulted in measured gain differences of up to 8 dB.

Conclusions: Careful consideration of selected test stimulus for measuring hearing aid gain is recommended.

Sound field measurements of nine speech-shaped test stimuli from five analyzing systems are compared with the ANSI standard (1992) specified speech spectrum recommended for hearing aid measurements and the International Long-term Average Speech Spectrum (ILTASS). Most stimuli closely duplicate one of these references that differ substantially in spectral shape. The effect of the difference between the two references on hearing aid measurements is presented and discussed, and an argument is put forward for using a test stimulus that most closely approximates ILTASS.

National Acoustic Laboratories, Chatswood, NSW, Australia.

Address for correspondence: Gitte Keidser, NAL, 126 Greville St, Chatswood, NSW 2067, Australia. E-mail:

© 2010 Lippincott Williams & Wilkins, Inc.