An apparatus for detecting acoustic signals in housing is disclosed. The housing may be housing of a wellbore, riser, tubular or pipeline or the like for transporting fluids or housing of a vessel for storing fluids. The apparatus comprises a longitudinally extending tube having an internal surface and an external surface, a longitudinally extending fibre optic cable disposed within the tube, and one or more than one longitudinally extending outer fins radially extending outwards from and coupled with the external surface of the tube. The outer fin is configured to project towards the housing and allows fluid between the external surface of the tube and the housing when the apparatus is positioned in the housing. The apparatus may alternatively comprise a longitudinally extending fibre optic cable coated with a coating and one or more than one longitudinally extending outer fin radially extending outwards from and coupled with the coated fibre optic cable.
