**2.4.1 FM systems**

20 Hearing Loss

coded electrical signals from the transmitter and delivers them to the array of electrodes that have been surgically inserted into the cochlea. The electrodes stimulate the fibers of the auditory nerve and sound sensations are perceived. Figure 12 depicts a series of stages of the speech processor of a typical cochlear implant and the associated processing waveforms

> **COCHLEAR IMPLANTS BTE BMD**  Device User Device User

Fig. 12. Block Diagram of a typical cochlear implant and processing waveforms

Other devices are employed to assist individuals with hearing impairment who have not previously experienced benefit with hearing aids or cochlear implants alone. Hearing assistive technology systems (HATS) are devices that can help patients function better in their day-to-day listening and communication situations. HATS can be used with or without

at each stage (Miller, 2006, as cited in Loizou, 1998).

Table 2. Styles of Cochlear Implants.

**2.4 Hearing Assistive Technology Systems** 

FM systems operate on special frequencies. A receiver worn around the neck transmits sound to the hearing aid. The sound comes from a transmitter microphone used by a speaker, although in many public places, the transmitter is built into the general sound system.

Because of their flexibility, mobility, and sturdiness, these systems are among the most commonly used HATS. Studies have shown that FM systems have the best results when implementation is carried out early in the amplification-fitting or cochlear-implant process. Also, infrared wireless headset are available for television listening and interface. However, there are other systems, denominated sound-field systems, which assist listening for all of the children in the classroom. The teacher speaks into a microphone transmitter and his/her voice is projected through speakers mounted around the classroom.
