Vent
In the earmold/shell, a small opening or tunnel runs from the faceplate (the side of the earmold facing out of the ear) to the tip side of the earmold. This opening is called a vent. It can have a number of functions; it ventilates and prevents moisture building up in the ear canal; the opening allows some sounds to be heard naturally through the ear canal without being processed by the hearing aid; and it can make the wearer's own voice sound better.