What is auditory desensitisation?
Auditory desensitisation aims to reduce the over-sensitivity of the hearing system to the sounds that someone finds uncomfortable.
If this is a very specific sound source, it may be easy to design a list of noises with which the person does and doesn't cope well - sounds that are less easy to categorise can prove more difficult.
A tape recording of sounds played by the child at their own comfortable level may be helpful. In some cases, this approach may be undertaken by the family, without requiring professional support.
Noise generators
Noise generators play an important part in the auditory desensitisation process. These small devices look like hearing aids and produce a steady, gentle noise with a volume control, allowing the noise level to be turned up or down.
The aim of using noise generators is to improve a person's ability to tolerate normal exposure to sound, by reducing the sensitivity of the ear. Although wearing the noise generator can mask the adverse sounds, the device is intended to provide long-term, low-level noise exposure while maintaining normal exposure to everyday noise. There is no possibility of damage to the hearing through use of a noise generator and benefits have been shown even when the generator is not in use, with longer-term improvements in the person's over-sensitivity to noise. Most adults using a noise generator report that, over a period of around one year to eighteen months use, hearing sensitivity becomes much more normal.
This is an established method of treating hearing over-sensitivity and is used in many audiology departments in the UK. There should be someone in your local audiology department who is able to advise you on the availability of this technique.
Hyperacusis can be managed most effectively by using noise generators in parallel with a programme aimed at reducing the fear and anxiety associated with sound exposure.
Fitting the device
Noise generators are worn behind the ear in a similar way to a hearing aid. The sound is fed into the ears through an ear mould which is specifically designed not to block the ear canal, allowing background noise to be heard normally. The ear mould and device must be comfortable and secure so that it is possible to build up the number of daily hours of use over time in comfort. As hearing sensitivity usually occurs in both ears, both ears will usually be fitted.
Setting the volume level
The device has a volume control which should be set so that the noise level is just audible. The sound level should not be intrusive in daily activity and, even if the background sound levels increase to a level that the noise generator can no longer be heard, the volume setting should remain the same. Only if the background noise level is uncomfortable should the volume be increased to cope with the discomfort.
Daily duration of use
The aim is to build up the length of time the device is worn to at least six hours a day. As the wearer becomes accustomed to wearing the device, it may be helpful for him/her (or, for a child, his/her parents) to keep a short-term diary of use and its perceived effects. This is not to raise the profile of the hearing sensitivity, but to keep a note of changes in reaction to sounds while the noise generators are being used.
Increasing the volume
When the individual has been using the noise generators quite comfortably for six hours a day without any problems, the level of the noise output should be fractionally increased. The new level should not cause problems, though the patient may need time to adjust to it. Again, when s/he is able to easily tolerate the new level, the sound level should be increased. This gradual increase in output should be used to improve the patient's ability to tolerate different environments in everyday life.
There is no set level that the wearer must reach, but when s/he can tolerate all the typical noise situations with the generators on, there is no need to continue to increase volume levels.
(In practice, with children who have been fitted to date, there has usually been immediate acceptance of the maskers, and they have quickly got used to the volume change.)
At this point, the reliance on using the maskers can be reduced (but don't over-challenge a child with situations s/he is nervous about), either by gradually reducing the volume level, or by reducing the hours of masker use.
Only when the patient can clearly cope in all circumstances without their maskers is the process complete and the brain's 'volume control' mechanism reset.
How long will it take?
Typically, after using noise generators for 12 to 18 months most people find a long-term improvement in their sensitivity without the need to use noise generators. Although it is impossible to predict exactly how long the process will take, the desensitisation should still be carried out over a finite period of time which will be set by the consultant or audiologist.
