Chapter 9 - Hearing Aids

Abstract

Hearing loss results in reduced ability to understand quiet sounds and loss of speech understanding, especially in noise. Hearing aids are designed to remediate this. We describe the various types of hearing aids and techniques to amplify or transform high sound frequencies to lower ones so that they become audible. Whereas hearing aids alleviate the loss of hearing low-level sounds and speech, they may aggravate the understanding of speech in noise by reducing the signal-to-noise ratio. This results from the compression of the amplification of higher-level sounds compared to low-level sounds such as background noise. In addition, the limited dynamic range in the amplification impairs music appreciation. Modern hearing aids with larger dynamic ranges may alleviate this problem. Hearing aid processing has greatly improved with the arrival of digital hearing aids, and the more frequent binaural hearing aid fitting. Consequently, nearly all studies on the use of hearing aids show an increased quality of life, including improved cognition. The expected improvement in social engagement was not clear. Hearing aids potentially alleviate tinnitus, albeit that this is not a general finding.