Describe hearing aids with their types and problems.

Components and Types

• A hearing aid is an electronic device that amplifies sound and delivers it to the ear.
• Its essential components are a microphone (sound to electrical signal), an amplifier and processor, a receiver (back to sound), a power source and an ear mould.
• Types by position — behind-the-ear (BTE), the most versatile, suiting any degree of loss including profound, easy to handle for arthritic or elderly hands, and usable with a perforated or discharging ear; receiver-IN-canal (RIC), cosmetically better with an open fitting; IN-the-ear, IN-the-canal and completely-IN-canal, progressively more discreet but less powerful, harder to handle, and more prone to wax and feedback; and body-worn aids, still used where cost and durability matter

Selection, Fitting and Problems

• Indications — broadly, a hearing loss causing disability, which is a matter of the patient’s needs rather than a threshold figure; conventionally a loss exceeding 30 to 35 dB in the better ear, though a musician or teacher may benefit at less
• Bilateral fitting is preferred where both ears are impaired.
• The better ear is aided first if only one aid is possible, though the choice depends on the discrimination score
• Speech audiometry predicts benefit better than the pure tone average, because an ear with poor discrimination gains little from amplification — and this should be measured before promising a result
• Fitting and verification — a well-fitting ear mould, which determines comfort, retention and feedback; real-ear measurement to verify that the prescribed gain is actually delivered at the drum; and counselling and realistic expectations
• The commonest reason AIDS end UP IN A drawer IS unrealistic expectation. The patient must be told that an aid amplifies but does not restore normal hearing; that background noise remains difficult; that their own voice will sound odd at first; and that acclimatisation takes weeks to months of consistent use
• Common problems and their causes — feedback (whistling) from a poorly fitting mould, wax, or the volume set too high, which is much the commonest complaint; occlusion effect, the booming of one’s own voice, relieved by venting the mould; discomfort from loud sounds from recruitment, managed by compression; otitis externa and mould allergy; wax accumulation, since the mould obstructs migration; and battery and handling difficulty in arthritic or visually impaired patients