Among others in order to provide efficient and manufacture-friendly configurable silencers, with preferred noise attenuation and pressure-drop characteristics, there is disclosed a silencer with a casing (3) having a longitudinal centre axis and at least one inlet (8) and at least one outlet (9) and at least one internal silencing section (2) extending between the inlet (7) and the outlet (8). The silencing section is along the longitudinal centre axis geometrically delimited by an inlet face (12) and an outlet face (13) and, in a direction transverse to, preferably perpendicular to a longitudinal centre axis, comprising a core region. The silencing section further comprising at least three oblong slots (18) extending outwards from the core region towards the casing (3) and extending from the inlet face (12) to the outlet face (13). The side walls of the slots (18) being essentially plane along an outwards extension.