Vent
In the ear mould/shell, a small opening or tunnel runs from the faceplate (the side of the ear mould facing out of the ear) to the tip side of the ear mould. 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 child's own voice sound better.