Harvey Dillon

In R.C. Seewarl (Ed.) A Sound Foundation Through Early Identification, Pp 65-76, Phonak: Stafa, Switzerland

Abstract

There are three ways in which the mismatch between the wide dynamic range of sounds in the environment and the narrower dynamic range between the threshold and discomfort level of a hearing-impaired person can be handled. One is to allow the most intense parts of a signal to be compression limited, or for those with an extremely profound hearing loss, peak clipped. The second is to use wide dynamic range compression. The third is to aim to have only the more intense parts of speech above threshold. If any one of these mechanisms is excessively relied upon, poor intelligibility is likely to result. An optimal fitting strategy for people with severe hearing loss will thus involve a combination of all three of these mechanisms so that each can be used to a limited degree. It is argued that our best guide to amplification requirements for babies and young children are the real ear requirements for adults with the same hearing loss. If variations from the adult formula are appropriate, the variations most likely to be useful are increased gain for low-level sounds, and decreased gain for high-level sounds. This therefore requires a higher compression ratio.