The present invention relates to a receiver module being adapted to be positioned in an ear canal, the receiver module comprising a receiver having a receiver housing, said receiver being adapted to receive a time dependent electrical signal, said receiver further being adapted to generate outgoing acoustic waves via an output port in the receiver housing in response to the received time dependent electrical signal, and expansible means surrounding at least part of the receiver housing, said expansible means having an opening aligned with the output port of the receiver housing so as to allow the generated outgoing acoustic waves to penetrate away from the receiver module and into the ear canal.