Friday 6 December 2013

How Do Hearing Aids Work?

Hearing aids – such a brilliant little device. Anyone who suffers from hearing loss knows exactly how valuable they are; they make life so much easier! You don’t have to annoy the neighbours with how loud you have your television; you don’t have to strain to hear someone over the background noise of a restaurant; you don’t have to try to read people’s lips… they’re fantastic.

But how do they actually work? Precursors to the humble hearing aid differ vastly from the gadget we’ve all fallen in love with, with devices such as the “metal ear” (exactly what it sounds like, and exactly as useless as you might imagine) and the “hearing trumpet” (a metal cone that you put by your ear – it became more effective as it increased in size… you can probably see where this is going).
Even when you get to actual hearing aids, the early models were drastically different too – some of the “lightweight” models actually weighed half a stone! Thankfully we’re not struggling with anything quite so cumbersome any more: modern hearing aids that are rechargeable are feather-light, super-compact and incredibly convenient.

Let’s take one apart and look at the insides!

The Mic
Probably the most obvious of all the various elements is the microphone. When a sound wave comes toward you and hits the mic, the microphone changes it into an electrical impulse – this allows it to be amplified accurately.
The more recent advances in hearing aid technology have resulted in the directional microphone. This little beauty can filter out sounds coming from behind you – this lets you hear the thing you’re focusing on much more clearly. Great!
The Amplifier
The amplifier… well, it amplifies. It’s really that simple. It comes after the microphone, taking the mic’s electrical impulses and increase the volume somewhat.
The vast majority of amplifiers are made up of two parts – the pre-amplifier and the power amplifier. The pre-amplifier, as you might have guessed, comes first: it increases the input signal by a small amount, before putting it through to its more powerful cousin who does the real heavy lifting.
Amplifiers are measured both in total amplification gain and in terms of power consumption. To discover how strong an amplifier you’ll need, you should get audiogram results from a hearing test.
The Receiver
The receiver takes those amplified signals and converts them back into sound. This is a complex process, so the receiver tends to be the big bit that’s visible to other people.
Smaller models, like ITC (In the Canal) hearing aids, tend to provide lower levels of amplification simply because the receiver has to be so much smaller. This means that if you suffer from serious hearing loss, we’d recommend the traditional BTE (Behind the Ear) version.
The Battery
Now, we don’t need to explain very much about the battery, as its function is more than slightly obvious, but it is incredibly important so we’d be remiss if we failed to mention it!
These used to be massive, but nowadays they’re minuscule zinc-air batteries that can last for a week or so of heavy use

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