Selection and fitting

Abstract

The primary purpose and function of hearing aid systems is to enable hearing impaired people to make maximum use of their residual hearing area. A system should therefore provide maximum speech intelligibility, maximum useful information from other sounds, minimum interference from unwanted noise, and minimum distortion. The aim will normally be to provide amplified speech that is as clear and intelligible as possible, with the provision also of important background sounds, such as a ringing doorbell, or the sound of an approaching car. These environmental sounds are important not only as warnings, but also as providers of general information about our environment, which is important psychologically. Unfortunately, background noise can, and does, interfere with the speech signal and it can be difficult, or even impossible, for hearing impaired people to separate the sounds they want to hear, from those they do not. This is partly due to the defective hearing mechanism, which is especially notable where cochlear damage has been sustained, and partly to the restrictions inherent in a hearing aid.