An application of the articulation index to hearing aid fitting

Abstract

It is often assumed that the articulation index (AI) is a sensitive and appropriate metric for making comparisons among frequency‐gain characteristics of hearing aids, and that the characteristic yielding the highest AI will result in the best speech intelligibility score. In evaluating these assumptions, 12 hearing‐impaired subjects listened to nonsense syllables under conditions of amplification prescribed by the NAL [D. Byrne and H. Dillon, Ear Hear. 7, 257–265 (1986)] and POGO [G. A. McCandless and P. E. Lyregaard, Hear. Instrum. 34, 16–21 (1983)] hearing aid fitting formulas. These two prescriptive methods recommend similar frequency responses, although the POGO consistently provides more overall gain. In a third condition, the goal of amplification was to insure that the speech was fully audible (AI = 1.0). Results suggest that the articulation index is useful for predicting percent‐correct intelligibility scores for some, but not all, of the hearing‐impaired subjects. Interestingly, the AI = 1.0 condition did not necessarily yield the best percent‐correct intelligibility score. [Work supported by NICHHD T32 HD‐07151, NINCDS NS 12125, and the Bryng Bryngelson Communication Disorders Research Fund at the University of Minnesota.]