Besides the hearing instrument itself, it is important because it fulfills multiple functions for acoustics and better hearing.

One of the most important tasks of the earmold is to amplify the transmitted acoustic sound and noise to the eardrum. It also improves the positioning and hold of the hearing instrument behind the ear.

An important aspect of the earmold is to seal the auditory canal. This acts as a gasket and prevents acoustic feedback.

Feedback occurs because some of the sound amplified by the hearing aid is sent outwards from the hearing aid receiver, "loudspeaker" then picked up again by the hearing aid microphone. The sound is then re-amplified and sent outward and once again picked up by the microphone. This becomes an infinite loop, creating the tonal squeal that can also be heard by other people.

Getting the right fit for your earmold is one way to prevent feedback. There are different forms and types of earmolds. You and your hearing health care provider will have to determine exactly which earmold is best for you.