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How do audiologists select hearing aids?

Hearing losses vary considerably in degree and configuration so it is important that each hearing aid is set to each individual's hearing loss.

When an Australian Hearing audiologist fits a hearing aid, they use a set of scientifically validated mathematical formulae to work out just how loud the hearing aid should be for that person in order to optimise the hearing they have. When an ear has a hearing loss, particularly in the case of sensorineural hearing loss, it is just as sensitive to loud sounds as a normal ear. For instance, a sound pressure level of 110dB will be just as uncomfortable for someone with a severe hearing loss as it would be for someone with normal hearing. When setting the hearing aid it is important that sounds are made audible but not intolerably loud, in order to ensure speech understanding is optimised.

The particular formula Australian Hearing currently uses to prescribe hearing aids is known as the NAL-NL1 prescription. This is based on extensive and thorough research undertaken by Australian Hearing's research arm, the National Acoustic Laboratories (NAL), over more than 20 years.

The procedure aims to maximise the amount of speech signal received by making all the amplified frequency bands of speech equally loud while achieving the best level of intelligibility and comfort.

The hearing aid selection procedure includes various adjustments, the main one being to allow for the fact that the low frequencies of speech are more intense than the high frequencies and hence do not need to be boosted as much to reach the person's most comfortable listening level.

Research has shown that simply trying to make all the sounds of speech loud enough to be heard does not give a good hearing aid fitting. Instead it can result in amplified speech which is uncomfortably loud, unclear and distorted. The procedure recommends how much gain or"loudness" should be added to soft, moderate and loud sounds to allow softer parts of speech to be heard and louder sounds to be comfortable.

Using the formulae is just the first step. Some form of assessment is then performed to ensure that your child is receiving the optimal hearing aid response for their hearing loss. Any feedback you can give on how your child is performing with their hearing aid(s) assists us. Your child will be regularly seen for aided and unaided assessment and review.

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Information provided by Australian Hearing. Reproduced with permission.
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14-Nov-2015 7:47 PM (AEST)