INSIDE A HEARING AID
The main components of a hearing aid are :
- An input transducer, (a) microphone or (b) telecoil
- An amplifier with volume control, filters, automatic gain control (AGC) and max. output regulation.
- A receiver (loudspeaker)
- A battery
Fig. 3.14 Simplified diagram of a hearing aid: 1. Microphone, 2. Telecoil, 3. Input amplifier, 4. Filters, 5. Volume control, 6. AGC/limiter, 7. Power amplifier, 8. Receiver.
The Microphone
The microphone converts sound waves into electrical signals. The electret microphone is the most commonly used type. It is a special type of condenser microphone with a built-in low-noise preamplifier. The ...
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