Not so very long ago the only hearing instruments available were 'analog' hearing aids. What these hearing instruments did was use a microphone to pick up a sound, amplify it, then send it to your ear using a loudspeaker.

And then came along Digital Signal Processing (DSP) and suddenly there were new solutions to old problems. Hearing instruments that use this technology are called Digital Hearing Instruments, and it's like having a computer in your ear.

Here's a simple overview:

1. The sound is picked up by the microphone and converted into numbers (represented in "binary code", a language understood by computers).
2. Those numbers are then manipulated by a computer-chip in the hearing instrument.
3. After the numbers have been manipulated they can be converted back into the now amplified sound and played out through the hearing instrument's loudspeaker.

That's all that 'digital' really means. As with all computers, there are different levels of sophistication available, from a very basic hearing instrument to a very advanced hearing instrument. It all depends on how good the computer-chip is and how it's programmed.

Here's where it gets clever...

Let's take a look at some of the things the more advanced digital hearing instruments can do once the sound is converted to numbers.

1. The computer can recognise what those numbers mean. Some numbers it will recognise as speech; some it will recognise as background noise; some it will recognise as feedback.
2. The computer can be programmed to react differently to the different sounds it recognises: if it recognises background noise, it can supress it. If it recognises speech, it can enhance it. If it detects feedback, it can generate an "anti-noise" to cancel the feedback out (this is known as 'phase inversion').
3. The computer also has information about your hearing test so it knows what sort of sounds you can hear perfectly well and what sounds you have difficulty with.

And all this happens in a fraction of a second, quicker than it takes your brain to process a sound!

	So rather than just increasing every sound it picks up, a good Digital Hearing Instruments is clever enough to distinguish between sounds and selectively increase the ones you need help with.

• The electronics for digital hearing aids are smaller which means they can fit into smaller hearing aids.
• They're more reliable as they use fewer components.
• The sound quality is better.
• They can use advanced calculations to imitate how the human cochlea (inner ear) works.
• They can make decisions based on what sounds they are hearing; for example, deciding to direct a microphone towards speech and away from background noise.
• They have plenty of room for 'growth'* so if your hearing loss changes at some stage, the hearing instrument can re-programmed to change with it.
  (*depending on which hearing instrument you have and how much your hearing changes.)

All these advantages make them particularly good at:

• Automatically turning up quiet sounds, but turning loud sounds down.
• Having different programmes for different listening situation, e.g. listening to music.
• Detecting when you've entered a noisy room so they automatically switch to a more suitable programme.

"Digital" has become a bit of a buzz-word. Just because something is "digital", it doesn't mean it uses all the sophisticated features we mentioned earlier (such as automatically directing a microphone, or switching to the appropriate programme), so it is important to know what the digital hearing instrument you are buying is capable of doing.

From time to time you will see advertisements for very cheap digital hearing instruments. Be careful: a very cheap digital hearing instrument is unlikely to have all the features of a more expensive one.

So it all boils down to what features do you need. Some of that will be based on your hearing loss, your lifestyle and your personal preference. Discuss it with your hearing aid audiologist.

	Confused? At Broom Reid & Harris we will advise you on the best hearing instrument for you.

Digital hearing instruments and some non-digital hearing instruments are 'programmable'. What this means is that we can link up your hearing instruments to a laptop computer (or handheld device) and use the computer to change the settings of your hearing instrument.

For example, say you have a cold and you find you’re not hearing as well as normal, we can re-program the hearing instrument to give you a bit more power. When your cold has gone we can change it back again.

Or say, for example, you have been wearing your hearing instrument for a couple of weeks and you find that certain noises are too loud. We can adjust the settings with the computer to selectively turn down that type of noise.

	Free fine-tuning for the lifetime of your hearing instrument: Once you have bought a hearing instrument from Broom Reid & Harris this ‘fine tuning’ is free for the lifetime of your hearing instrument.

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