Next: EARTH LEAKAGE CIRCUIT BREAKER (ELCB)

EAR MOULD

Typical Number in Hospital:

Cost Bands:

References: 3,4

This is a hollow plastic plug made from an impression of the outer ear and intended to form an almost airtight seal for the coupling tube from a hearing aid to the ear. If an adequate seal is not achieved then there will be a substantial loss of sound amplitude reaching the ear, particularly at lower frequencies. This causes a problem in growing children if the ear mould is not delivered soon after the impression has been taken, and may cause the hearing aid to whistle. An intentional leak (or 'vent') allows the low-frequency sounds to be reduced if this is beneficial to the patient.

Ear moulds may be manufactured in the hospital (audiology department) but more often the impression of the ear is sent to a specialist contractor. To make ear moulds in the hospital the procedure might be to take the outer ear impression using a quick curing (2-5 min) filler. Once set this may be coated with wax from a heated wax bath to slightly enlarge the impression. A plaster of paris cast is then made and this is filled with a liquid which cures to an acrylic polymer. After removal from the plaster it is trimmed and polished, and the sound channel is drilled.

If these processes are undertaken in the hospital department, attention must be given to the health and safety requirements related to the solvents used and machining techniques.