Most hearing aids will whistle at some time or another. This whistling that other people can hear is known as feedback.

Feedback occurs when the microphone picks up the sound coming out of the hearing aid and amplifies it.

Modern hearing aids use a range of internal feedback management systems that the audiologist will set when necessary and help to reduce the amount of whistling heard. However, the most likely reason for feedback is that the earmould is not a good fit. This allows sounds to ‘leak’ from around the earmould and be picked up by the hearing aid’s microphone.

Because young children grow quickly, new impressions should be taken and earmoulds replaced regularly. For very young babies, this may be at least every month.

Possible other causes include:

Earwax

Earwax can cause feedback as more sound is reflected back out of the ear. If an earmould is a good fit but it has started to produce feedback, this could be an early sign of earwax. It is important not to try and remove the wax yourself as putting cotton buds into the ear can push the wax in deeper. Ask your audiologist or family doctor (GP) to check the ears for wax instead.

Faulty elbow (tone hook)

The elbow is the plastic hook that fits between the hearing aid and the earmould tubing. If it is faulty (for example, if it has a hole or is cracked, split or chewed) it is very important to replace it. It must be replaced with exactly the same type of elbow. You can get a replacement from the clinic that issued your child’s hearing aid.

Feedback from the aid itself

Take apart the hearing aid and the earmould. You can do this by gently pulling apart the soft tubing of the earmould from the hard plastic elbow of the hearing aid.

After checking that the elbow is in good condition, press a finger over the end making a good seal. When the hearing aid is turned on you should not get any feedback. This means that the aid is working properly.

If you can hear whistling, there is a problem inside the hearing aid and it should be returned to the clinic for repair.

Jaw movement

Jaw movement may make the earmould come out slightly and cause feedback. Using a different earmould material or a new earmould with a different length meatal tip might help.

It could be that a different length of earmould tubing may be better. Try using petroleum jelly or a special cream, such as Otoferm or Aquagel. A small amount can help to make a seal between the earmould and the ear itself.

In some cases this can help reduce feedback and also help to slide the earmould more smoothly into the ear.

Poor earmould

Problems can start when the earmould becomes hardened and cracks due to age. A new earmould needs to be fitted as soon as possible.

Small ear canal

Children with particularly narrow ear canals can sometimes have problems with feedback as sound reflects off the ear canal walls more easily. Certain groups of children are more likely to have narrow ear canals, e.g. children with Down’s syndrome.•

Feedback in young babies

If you have a young baby who is wearing behind the ear hearing aids, you may find that feedback occurs when you hold your baby close (for example, while feeding).

Feedback may also happen when the baby is lying down with their hearing aids on.  You may need to hold your baby in a different position or take the hearing aid out for a short time.

If the feedback becomes a problem, talk to your child’s audiologist or Teacher of the Deaf.