Hearing aid selection for the 1990s: where to?

This paper discusses trends and issues in selecting amplification for new, mainly nonlinear, types of hearing aids. Some-concerns are that nonvalidated prescription formulae may proliferate; that, through concentration on loudness normalization, alternative rationales are not being evaluated; and that most new fitting procedures for nonlinear hearing aids ignore the findings of research with linear amplification. A possible philosophical concern is that the hearing aid fitter may lose control of the fitting process. The achieving of any particular loudness relationship, among different frequency components of amplified speech, may be unimportant in itself but may be critical for achieving other objectives such as maximizing audibility over a wide frequency range when speech is at a comfortable level. Amplification selection should seek to achieve objectives by the simplest means (linear frequency shaping, automatic volume control) and should proceed to more complex, but potentially detrimental, processing (syllabic compression) only to the extent necessary. New prescriptive procedures should build on established procedures because, for typical speech levels, amplification requirements should be similar, regardless of whether linear or nonlinear amplification is used.