Most mammals have two ears to receive sounds from each side of the head, technically known as binaural hearing. Bi meaning 'two' and aural meaning 'ears'. The human hearing mechanism is the most advanced stereophonic wonder known to man. With all its amazing accuracy and versatility, it provides the listener with space perception, depth perception and balance.

Hearing does not happen in your ears it happens in your brain. Your brain requires reliable information from your ears so that it can decipher sound. Using just one hearing aid when hearing test results indicate that two are needed reduces your brain's chances of hearing and understanding considerably, as well as removes your ability to perceive depth and space. Binaural hearing allows the brain to process sound more precisely by providing the following benefits:

1. Localisation - Balanced hearing is imperative for our ability to hear where a sound is coming from, it can be a source of embarrassment i.e. where is the sound coming from when someone speaks, or potential danger i.e. 'which direction is that motorbike coming from' when crossing a road. Our brain instinctively locates a sound source by measuring tiny differences in duration and intensity between each ear. When these minute differences are perceived by the brain it enables us to locate the sound source. This allows the ears to provide 360 degrees of perception, something unique to our auditory sense. Using one hearing aid when two are needed reduces the ability of the brain to localise sound as the diagram below illustrates.

One Ear	Two Ears

2. Improved clarity in noise - Two ears working together give us the ability to isolate one sound from another. By perceiving differences in duration, pitch and loudness the brain can select a specific sound or voice and concentrate on it even in the presence of background noise. Voice discrimination in a noisy environment is difficult with two ears, when this is reduced to just one ear the task becomes virtually impossible

3. One is less than half - Contrary to popular belief, one ear working less effectively than the other can have a significant impact on daily life. Hearing with one ear is like trying to see with one eye, it's possible but not as effective. That's why people do not tend to wear monocles anymore. They became obsolete when eye specialists discovered the importance of balanced vision. Improving the hearing in one ear whilst the other remains impaired causes problems with loudness, clarity and auditory depth.

4. Less Power = greater comfort and clarity - When two hearing aids are worn, your ears work together and as a result lower volume settings are required enabling more comfortable hearing. You will experience greater efficiency and clarity with two hearing aids as opposed to monaural listening. Sounds are evenly distributed between the ears so loud sounds are more comfortable and listening is less stressful and importantly, more natural.

5. Stereo Listening - This gives depth perception. Anyone who has enjoyed music in stereo, compared to mono, knows the difference. Mono makes all sounds seem shallow, flat and unnatural. Your brain has the ability to hear in stereo but to do so needs sound input from both ears. Again, this makes sound clearer and more natural.

6. Auditory Deprivation - Each ear sends different signals to the brain, the two halves of your brain work in harmony to give an auditory image. The ears' sound signals travel up the brain stem via complicated pathways. Some cross over and eventually stimulate the other side of the brain, while others stimulate the same side. These very complex patterns of stimulation make up auditory intelligence (see schematic diagram below). If the two halves are not sharing their signals i.e. in the case of one ear being aided and the other not, then the brain gradually loses some of its processing ability due to a lack of stimulation, as a result auditory deprivation may then occur. It is similar to an unused muscle; the unused auditory fibres may atrophy (waste away).

Pathways when sound enters both ears equally	Pathways when sound enters only one ear

7. Less Feedback - With wearing two hearing aids as opposed to one the likelihood of feedback (whistling) is reduced due to the lower volume setting necessitated by two aids compare to wearing just one.

8. Less tiring - Many binaural hearing instrument wearers report that listening in conversations is more enjoyable. They find listening with two ears less stressful and tiring than with just one ear aided.

Sound Advice (Hearing Ltd) will advise you as to the relevant advantages of binaural hearing for your particular hearing needs and lifestyle once we have conducted a thorough hearing test. It may be that due to dissimilar hearing losses in each ear, that a monaural fitting may be adequate for your particular needs.

Remember quality of sound is better quality of life.

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