Auditory handicap of hearing impairment and the limited benefit of hearing aids

TLDR

Hearing loss for speech can be decomposed into class A attenuation and class D distortion, the latter reducing the speech‑to‑noise ratio. The article aims to clarify hearing impairment as a communicative handicap in noise and to model the limited benefit of hearing aids. The authors employ a quantitative model to demonstrate why hearing aids have limited applicability. Class‑D hearing loss, which reduces the speech‑to‑noise ratio, accounts for about one‑third of total loss, begins at ~24 dB, and is not compensated by hearing aids, whereas class‑A losses are.

Abstract

The aim of this article is to promote a better understanding of hearing impairment as a communicative handicap, primarily in noisy environments, and to explain by means of a quantitative model the essentially limited applicability of hearing aids. After data on the prevalence of hearing impairment and of auditory handicap have been reviewed, it is explained that every hearing loss for speech can be interpreted as the sum of a loss class A (attenuation), characterized by a reduction of the levels of both speech signal and noise, and a loss D (distortion), comparable with a decrease in speech-to-noise ratio. On the average, the hearing loss of class D (hearing loss in noise) appears to be about one-third (in decibels) of the total hearing loss (A + D, hearing loss in quiet). A hearing aid can compensate for class-A-hearing losses, giving difficulties primarily in quiet, but not for class-D hearing losses, giving difficulties primarily in noise. The latter class represents the first stage of auditory handicap, beginning at an average hearing loss of about 24 dB.