An application of the articulation index to hearing aid fitting.

The application of the articulation index (AI) model to the fitting of linear amplification was evaluated for 12 subjects with sensorineural hearing loss. Comparisons were made of amplification characteristics specified by the NAL (Byrne & Dillon, 1986) and POGO (McCandless & Lyregaard, 1983) prescriptions, as well as a procedure that attempted to maximize the AI (AIMax). For all subjects, the relationship between percent-correct scores on a nonsense syllable test and AIs was monotonic for the two prescriptions, indicating that the AI was effective for comparing conditions typical of those recommended clinically. However, subjects having sloping high-frequency hearing losses demonstrated nonmonotonicity due to poor performance in the AIMax condition. For these subjects, the AIMax condition required much more gain at high than at low frequencies, circumstances that Skinner (1980) warned will cause less-than-optimal performance for individuals having sloping high-frequency hearing loss.