Silencer for an auxiliary power unit of an aircraft

An aircraft comprising an auxiliary power unit and a silencer, the silencer comprising:

• a longitudinal inlet section;
• an outlet;
• a housing downstream of the inlet section;
• a flow channel, arranged in the housing, comprising a porous wall material,
• wherein between the housing and the flow channel an intermediate space is created, the intermediate space being divided by at least one outer partition into at least first and second outer cells arranged around the flow channel, and
• a central body comprising a casing permeable to gas in at least in one region, the central body being arranged in the interior of the inlet section and upstream of the flow channel and the at least one first and second outer cells and comprising a plurality of inner partitions dividing the central body into a plurality of inner cells,
• wherein the resonance frequency of the inner cells corresponds to the natural frequency of the first radial mode in a channel formed between the central body and the inner surface of the inlet;
• and
• wherein the inlet of the silencer is connected to an exhaust gas outlet of the auxiliary power unit.