The present invention relates to a muffler for a line conveying gas and airborne sound, in particular for an exhaust system of an internal combustion engine, preferably in a motor vehicle. The muffler has a housing in which there are at least two inside pipes for carrying gas in the interior of the housing and which contains at least one inside plate for reinforcing the housing. The two inside pipes are inserted one inside the other in a sliding seat area and are axially movable in relation to one another.