Generally fabricated from an impression of the individual ear to be fitted with a hearing instrument.
To get an individually fitted hearing aid, it is necessary to make a casting of the ear canal to ensure that the earmould fits perfectly. No two ears are alike and especially children need to have new earmoulds made regularly as their ears grow and mature.
When casting, the ear canal is filled with a kind of wax which is subsequently removed after a couple of minutes. This procedure does not hurt but it does feel a bit strange – a bit like having your ears filled with water. The cast is then used to make the actual earmould which is then attached to the rest of the hearing aid. This may take days or a few weeks.
Some of the problems that may occur include:
- Unpleasant sound blockage – also known as the “occlusion effect”
- Acoustic feedback
- Cerumen (earwax) build-up
- Allergic reactions
Sound blockage makes it difficult to hear others. Vents placed in the earmould will often solve this problem. It is not unusual for these vents to be adjusted several times in order to get the desired effect.
Acoustic feedback is a kind of whistling sound that occurs when amplified sound escapes from any part of the hearing aid and reenters the hearing aid microphone. It is a phenomenon that occurs when the earmould does not fit tightly enough. This can make it difficult to make the vents that are needed to overcome sound blockage.
The earmould can also cause a build-up of cerumen (earwax) – especially when wearing tight earmoulds. Cerumen can reduce sound transmission and thereby making it difficult to hear.
Lastly, the materials used to produce the earmould can cause allergic reactions. In such cases, other hypoallergenic materials must be sought.