Abstract: The present invention relates to a receiver module adapted to be positioned in an ear canal. The receiver module comprises a receiver having a receiver housing and expansible means surrounding at least part of the receiver housing, the expansible means having a first opening aligned with an output port of the receiver housing so as to allow for generated acoustic waves to propagate away from the receiver module and into the ear canal, the receiver module further comprising encapsulation means partly encircling the expansible means, the encapsulation means being adapted to provide, in an expanded state of the expansible means, a second opening aligned with the output port of the receiver housing so as to allow for the generated outgoing acoustic waves to propagate away from the receiver module and into the ear canal.