Articulation index predictions for hearing-impaired listeners with and without cochlear dead regions

Abstract

Vickers, Moore, and Baer [J. Acoust. Soc. Am. 110, 1164–1175 (2001)] reported that hearing-impaired subjects with cochlear “dead regions” benefited from amplification of frequencies up to an octave above the estimated edge frequency of the dead region, but not beyond, whereas hearing-impaired subjects without dead regions did show benefit beyond this boundary. Dead regions are thought to have no functioning inner hair cells. Vickers et al. indicated that a clinical test for detecting dead regions would provide supplementary information that is important for hearing aid fitting. Furthermore, they suggested that the articulation index (AI) may overestimate the potential benefit of amplification for listeners with dead regions because the AI does not account for the presence of dead regions. To evaluate their claims, we conducted an AI analysis [H. Fletcher, Speech and Hearing in Communication (Van Nostrand, New York, 1953); H. Fletcher and R. H. Galt, J. Acoust. Soc. Am. 22, 89–151 (1950)]. Results show that the AI is generally accurate in predicting the consonant recognition test scores of Vickers et al.’s subjects irrespective of the presence/absence of dead regions. This suggests that audiogram differences account for the observed performance differences; it was not necessary to invoke dead regions to explain the speech test results. The results of the AI analysis are sufficiently accurate to call in to question whether a clinical test for dead regions would offer additional predictive information.