BRUSH UP ON YOUR AUDIOLOGY: THE OCCLUSION EFFECT

The echo of one’s voice is a common complaint of new hearing aid users – and it’s all thanks to the old “occlusion effect.”
Is your client complaining that they can hear the echo of their own voice when they wear their hearing aids? Does their voice sound hollow or booming?

They are probably experiencing the occlusion effect – a common issue for new hearing aid users. Luckily there are ways to fix the problem without ordering them a new set of hearing aids.

Here are the facts.


WHAT IS THE OCCLUSION EFFECT?

When an earmould or a hearing aid is placed in the ear, it partially blocks the ear canal. Due to this blockage, the user may hear his or her own voice louder, and the voice may also sound hollow, as if one was talking inside a barrel. This problem is most frequent with low frequencies.


WHAT CAUSES THE OCCLUSION EFFECT?

A prime cause of the occlusion effect is from vibrations in the wall of the ear canal.

When you are talking or eating
, vibrations from the vocal chords or sound generated by chewing is transmitted via the skull. This makes the walls of the soft part of the ear canal vibrate, acting like a sound membrane.

When the ear is closed by an earmould or shell, these vibrations create a much higher sound pressure level than in an open ear.

HOW CAN I HELP MY CLIENT OVERCOME THE OCCLUSION EFFECT?

The occlusion effect can be reduced or eliminated by a vent in the earmould or shell. This is an additional bore parallel with a sound bore. It connects the residual canal volume with the air outside the ear.

The larger the vent is, the more efficient the reduction of the occlusion effect. The vent diameter is chosen on the basis of the same criteria used with earmoulds - to reduce the occlusion effect and increase comfort, or to lower the low-frequency gain.

An open earmould can also be chosen to reduce the occlusion effect.

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