An acoustic silencer for dampening unwanted resonant and pressure pulses in a pipe or duct work and includes an expansion chamber having an enclosed volume through which a pipe or duct work extends, thereby defining an annular volume within the enclosed volume between the process pipe and the expansion chamber. An insert disposed within the annular volume extends along the length of the process pipe and forms an acoustic volume within the annular volume and defines a resonant passage length that is of a length so as to dampen one or more frequencies of the process pipe. An opening is formed through the process pipe along the length of the process pipe that extends through the expansion chamber and is in fluidic communication with the acoustic volume.

The phenomenon of resonance in a catalyst converter due to a flow of an exhaust gas is reduced without causing problems with vehicle layout, problems with manufacturing (higher manufacturing cost), or adverse influences on other facets of performance. An internal combustion engine includes an internal combustion engine main body having a fuel chamber formed in an interior, and a catalyst converter arranged in an exhaust flow channel of the internal combustion engine main body and provided with a catalyst for purifying the exhaust gas. The exhaust flow channel, which is upstream of the catalyst of the catalyst converter, is provided with a protuberance for disturbing the flow of the exhaust gas in the exhaust flow channel to reduce pressure pulsations of the exhaust gas.