Hearing Aids are electroacoustic devices typically worn in or behind the ear and are designed to amplify and modulate sound for the hearing impaired. The microphone converts sound into an electrical signal, the signal conditioning process amplifies and/or edits the signal, and the receiver (speaker) converts the signal back to sound. The battery powers the whole process.
Most hearing aids today are digital due to increased performance and flexibility, and include features such as advanced signal processing for noise reduction , filtering, and acoustic feedback (ringing) control. Special design considerations for hearing aids must be incorporated, i.e., they obviously must be small enough to fit in the ear. Electronics control the audio-processing path and are chosen for the specific benefits of real-time-speed (no time lags), compression/expansion by band, positive feedback reduction, noise reduction, and speech enhancement, as well as processing directional information.
