The mould is not, however, always perfect, so it is not unusual for the ear mould to require several adjustments before fitting and functioning properly.
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 than yourself. Vents placed in the ear mould 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 re-enters the hearing aid microphone. It is a phenomenon that occurs when the ear mould does not fit tightly enough. This can make it difficult to make the vents that are needed to overcome sound blockage.
The ear mould can also cause a build-up of cerumen (earwax) - especially when wearing tight ear moulds. Cerumen can reduce sound transmission and thereby making it difficult to hear.
Lastly, the materials used to produce the ear mould can cause allergic reactions. In such cases other hypoallergenic materials must be sought.