Resonance box for sound pressure level modulation for internal combustion engines

Engine comprising a flow channel (7) for gaseous fluids having means adapted to vary a sound pressure level of a sound of the gaseous fluids at at least one predetermined frequency, wherein said means comprises at least one side branch tube and/or at least one resonance box (8) for causing resonance at the at least one predetermined frequency, wherein an opening of the at least one side branch tube and/or an opening of the at least one resonance box respectively face an external opening (7a) of the flow channel.