I often see patients who have been given incorrect or outdated advice as to whether they should be fitted with one hearing aid or two. The answer is quite simple, if you have a hearing loss in both ears then a hearing aid is required in each ear. After all, the ears are just like the eyes and, unless you are Colonel Klink from Hogan’s Heroes, if you have two impaired eyes then you wear a pair of glasses, not a monocle.

Current research strongly supports the advantages of balanced binaural hearing aid fitting. Why? Firstly a part of our localisation abilities relies on the volume differences between the two ears. So a sound coming from one side should be louder in the ear on that side than the other ear. The brain analyses this volume difference and knows that the sound comes from the side where the sound is the loudest. If only one hearing aid is worn then the brain is unable to use this volume difference as the ear with the hearing aid in it will always seem louder than the untreated ear and localisation will always be towards that side.

Secondly there is a condition called an auditory deprivation effect. This effect occurs when you fit only one hearing aid to a hearing loss in both ears. Because the ear with the hearing aid is now doing the majority of the hearing and auditory processing, the hearing in the ear that is left unaided can decline at a much faster rate as the auditory system is not being stimulated to the same degree as the aided ear. In other words, the unaided ear and auditory system becomes lazy.
Another reason for fitting both ears is an effect called binaural advantage. Next time you try and talk in a crowded room, or even watch the TV with some background noise present, block one of your ears and notice how much harder it is to hear the conversation. This is an auditory processing effect, which occurs within the brain, that allows us to pick up speech sounds in the presence of noise much more effectively. The brain does this by talking to and fine-tuning both ears to attenuate the speech sounds more precisely. It requires information from both ears to do this adequately.

Many features in hearing aids that help you follow speech in noisy environments are designed to work together with a second hearing aid. For example, a directional microphone. When several people start talking at once most hearing aids change their directionality from picking up sounds all around to just picking up sounds in front. When only one hearing aid is worn then you don’t pick up sounds on the unaided side. Also, because the directional beam of the aided ear becomes narrower, it only picks up sounds on angles from zero to 90 degrees so you lose information from the unaided side altogether.

Finally most hearing aids now have Bluetooth connectivity, which basically enables you to use your hearing aids as headphones and stream the TV, music, telephones, microphones or any audio devices straight to the hearing aids. Should you only have one hearing aid then you lose the advantages of the increased sound quality and stereo effects.

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