Aids for People with Hearing Loss
A variety of technical schemes are used to assist people with hearing loss. Sound detection is usually by means of an external microphone or one within the ear canal, although the presence of sound is sometimes detected by a vibration sensor clamped to an outer member of the ossicular chain. After detection, the signal is processed to give it properties most useful to the patient. Finally, it is delivered to the listener as sound from a speaker, as a vibration delivered to the mastoid bone or to an inner member of the ossicular chain, or even as an electronic signal provided to nerve endings within the cochlea or directly to the brain stem. In this chapter, you will learn about some of the technological issues involved in each of these schemes.