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 arrangement surrounding at least part of the receiver housing, the expansible arrangement 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 elastic encapsulation material partly encircling the expansible arrangement, the elastic encapsulation material being adapted to provide, in an expanded state of the expansible arrangement, 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.