Occlusion Here you can read about occlusion, how it sounds and how to reduce it.

When an earmould or a hearing aid is placed in the ear, it partially blocks the ear canal. Due to this blockage, the user hears his or her own voice louder and the voice may also sound hollow as if one was talking inside a barrel. This phenomenon is called the occlusion effect.

The occlusion effect is caused by vibrations of the wall of the ear canal. When we 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, these vibrations create a much higher sound pressure than in an open ear. The sound pressure thus generated at the eardrum can be up to 30 dB higher in the occluded (closed) ear, depending on the frequency. The occlusion effect is a problem, especially at low frequencies (i.e. below 1 kHz).

Increased comfort with reduced occlusion

The occlusion effect can be reduced or eliminated by a vent in the earmould or shell. This is an additional bore parallel with the sound bore. It connects the residual canal volume with the air outside the ear. The larger the vent, the more efficient is the reduction of the occlusion effect. The vent diameter is chosen on the basis of the same criteria used with earmoulds, that is to reduce the occlusion effect and increase comfort or to lower the low-frequency gain.

Digital signal processing can help to reduce this sensation of occlusion. Senso Diva is provided with an occlusion manager, which adjusts the hearing aid’s signal processing to reduce occlusion.