Those who have severe hearing losses require a powerful amplifier. This amplifier is enveloped in a case smaller than that of a packet of cigarettes, which can be easily kept in the shirt pocket. A cord connects the receiver in the ear and the amplifier. Most of the hearing aids have adjustable controls. A small vibrator is clasped against the mastoid bone behind the ear with a headband if the hearing loss is due to some malformation of the ear canal or some dysfunction of the middle ear.

A more recent advancement for the deaf people, whose auditory nerves function is cochlear implant, is available to a limited degree. This device consists of electrodes, embedded in the cochlea of the inner ear to stimulate the auditory nerve. The electrodes are connected through the mastoid bone to a receiver surgically placed beneath the skin. There is a microphone near the ear that relays sound signals to a microprocessor, which in turn converts them into electric signals that, are sent to the transmitter behind the ear, then to the receiver and cochlear electrodes. However, the cochlear implant is a very crude version of the normal human sound.

A physicist from United States, George von Bekesy, is responsible for his most noted works in improvements in the design of hearing aids. He also won the Nobel Prize in the field of medicine and Physiology.

George von Bekesy