How hearing aids work

Digital hearing aids first became available in the 1980s but were not immediately popular because of their size and obtrusiveness. It wasn’t until the mid-1990s that technology improved to the point of allowing them to become more discrete that their popularity began to rise.

Even so, a great deal of mystique surrounds them and while many people have heard of their advantages over conventional aids, few really understand how they work and if their supposed superiority is all that it is made out to be.

Before the development of digital aids, the most popular hearing device available was an analogue aid. These are still very popular and use a microphone to pick up sound and convert it into electrical signals. The signals are then amplified by transistors and fed to the earphone so that the person using the hearing aid can hear them. The better analogue hearing aids compress the sound using something called “automatic gain control”.

This amplifies quiet sounds until they are loud enough to be heard, but gives less boost to sounds that are already loud so that the person using the hearing aid is protected against uncomfortably loud sound levels.

The idea behind this is that it should help the wearer when in very noisy places to hear the one voice or sound that he or she is interested in. Unfortunately, even with the better analog hearing aids, this does not work all that well.

Digital aids work on a completely different principle and strive to overcome the problem of hearing against a background of noise. They take the signal from the microphone and convert it into “bits” of data, numbers that can be manipulated by a tiny computer in the hearing aid.

This makes it possible to monitor and process sounds very accurately, in ways that cannot be done with analog aids. The best digital aids can be very finely adjusted to suit individuals and some even adjust themselves automatically to suit different sound environments.

Much work has been done on digital aids in an effort to get them to phase out or tone down back ground noise which makes it so difficult for deaf people to hear conversation in traditionally noisy places such as pubs or clubs etc.

Although most wearers seem to agree that digital aids do offer better quality of hearing on a one to one basis, in a noisy situation they are not a lot better than analogue aids.

To improve hearing in noisy situations studies seem to show that you need to wear aids in both ears, and if they have twin microphones, that is even better! Twin or dual microphones are a type of directional microphone that picks up sounds that come from in front of you much better than sounds to the side or behind you, making it easier for you to focus on what you want to listen to in a noisy place. Unfortunately, the very small, in-the-canal aids are too tiny to be fitted with twin microphones.

So, having decided a digital aid could be for you what next? Firstly, you have to remember that digital aids are programmable and need a skilled operator to set them up so do make sure that your audiologist is suitably qualified.

You should be offered a full hearing test and the results of this should be explained by the audiologist who will tell you just what sounds and frequencies you have difficulty in hearing. He or she will then demonstrate with the aid of headphones and microphones how your hearing can be enhanced by an artificial aid. You will be shown a choice of different aids ranging from behind the ear instruments similar to analog aids to very tiny, in-the-canal instruments that are not much bigger than a little fingernail!

As with an analog aid, a cast is taken of the outer ear canal which is taken away to be made up into an aid. Shortly afterward your aid is ready for fitting. Unlike analog aids that come ready to wear, digital aids have to be programmed.

The aid is fitted into the ear and attached to the audiologist’s small, portable computer. This allows the manipulation of the various bands of sound, allowing some to be toned down and others to be boosted. To get this exactly right often needs several sessions of fine-tuning so the wearer must be prepared to co-operate with the audiologist if he or she is to get the best from his or her aid.

This could take several weeks or even months as the user has to allow a period of time to get used to the aid and know what he or she is comfortable with.

Manufacturers claim that digital aids have a number of advantages over their analog counterparts apart from their ability to tone down background noise more efficiently. They can be made much smaller and so are more discrete, they produce clearer sound, batteries are no more expensive than those used in analog aids and perhaps most importantly, their life expectancy is much longer.

Audiologists generally expect analog aids to last from three to five years before they need replacing, either through just being worn out or through declining hearing ability.

Digital aids, barring physical accidents should last almost indefinitely. Any decline in hearing can be counteracted by reprogramming the aid, a few minute’s jobs by the audiologist, and very cheap to do.

This argument is used vigorously by private hearing specialists when justifying the high prices commanded by digital aids. They claim that once purchased the aid should last a lifetime. This may well be true, but you need to bear in mind that technology is improving all the time, and it could be that the current state of the art aids available today, will be replaced by something much better in five or ten years’ time.

Due to the high cost of digital aids, it is important that you establish a trial, money-back guarantee period before purchasing as you do need time to become accustomed to them in various noise situations.

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