Vincent Cumberworth BSc FRCS Consultant Ear, Nose and Throat Surgeon

Clementine Churchill Hospital Sudbury Hill Harrow Middlesex HA1 3RX
Private Secretary: Tel: 020 8872 3866 Fax: 0208872 3861

Information is supplied only upon the condition that the viewer will make their own determination as to the suitability of the information for its purposes prior to use. There will be no responsibility for information that is misused or misinterpreted and the information should not be used as a substitute for consultation with a health care professional. It is not possible to answer questions regarding individual cases or to enter into individual correspondence.

DEAFNESS

Sound is transmitted through the middle ear into the cochlea and in the inner ear the sound waves are converted into electrical signals. These then pass by nerves to the brain. The commonest cause of hearing loss is due to damage to the hair cells in the cochlea and accounts around 80% of such problems. From the 7½ million people in the United Kingdom have some degree of hearing loss with the common factors being age, infection or noise.

Types of Deafness

Conductive deafness involves a problem affecting sound passage either down the external ear canal or across the middle ear, such as excessive wax, fluid in the middle ear, perforation of the drum or damage to the sound conducting mechanism. This type of hearing loss can, although not always be correctable.

Sensori-Neural Hearing Loss from Cochlea

This is most frequently helped by a hearing aid, although sometimes other treatments are possible.

Analogue Hearing Aids

Hearing aids are able to help the hearing problems of around 5 million people in the United Kingdom. The initial referral from the general practitioner, generally to an ENT Surgeon or Audiologist and further hearing testing is likely to be arranged. If there is any asymmetry in the hearing thresholds or a significant conductive component or any other associated symptoms, then a review the ENT Specialist will be fairly certain.

A hearing aid consists of a microphone to the text sound, an amplifier to increase it and a speaker to transmit the amplified sound down to the ear. They are not able to restore hearing to normal.

Most analogue hearing aids compress the sound using “automatic gain control” (AGC) so that quiet sounds are amplified until they are loud enough but sounds that are already laugh are not amplified so much to avoid uncomfortable loudness levels.

Digital Hearing Aids

These take the signal from the microphone and convert it into “bits” of data which is then manipulated by a very tiny computer in the hearing aid. This allows more precise processing of sound and adjustment to individual needs. There can be different settings available for different listening conditions and these aids can adjust themselves automatically to different sound environments in many cases.

Often they are able to reduce steady background noise to enhance listening, although it can still be difficult to pick up out a single voice from ambient sound in a way that a normally functioning ear is able to do.


It is possible that wearing bilateral aids or hearing aids with twin microphones may be beneficial in noisy situations. The dual microphones can enhance awareness of sound all around.

Some digital hearing aids are able to use acoustic feedback suppression or feedback cancellation to reduce the background whistling which can be a problem due to feedback with hearing aids.

Many digital hearing aids will have a wide dynamic range compression which can be individually programmed and can also be self-adjusting. This often means that the initial fitting time is greater for a digital aid. Digital aids are, like analogue aids, available in behind the ear, “in the ear” or “in the canal” models and are not necessarily smaller.

Digital and analogue aids both have a T setting which enable sound to be picked up from a loop system or inductive coupler, rather than relying on amplification of sound directly. This can be useful in facilities which are equipped with loop devices. It does require a telecoil to be a part of the aid and may not be present in the very smallest type of aids.

 

© Vincent Cumberworth 2005