Abstract: A device for silencing a flow includes at least one acoustic chamber through-flowed by gas, e.g., exhaust gas, at least one inlet pipe and at least one pipe or passage interconnecting two chambers or a chamber and an exterior environment or chamber and is designed with such cross-sectional area transitions, between passages and the chambers that the sound attenuation achieved by the device is high while the pressure drop across the silencer is low and that high attenuation at low characteristic frequencies of flow systems are obtained. The device may contain at least one of diffusers, monolithic bodies and catalysts. The passages may be curved or helical so as to allow for a low natural frequency. Embodiments with resonance chambers attenuating at selected frequencies are disclosed. A method for operating a vehicle including a combustion engine and a silencing system is disclosed.

Abstract: A device (a silencer) for silencing a flow of gas, such as an exhaust gas, comprises at least one acoustic chamber (1, 2, 3) through-flowed by gas, at least one inlet pipe (6) for leading gas into the device and at least one pipe or passage (4, 12, 13) interconnecting two chambers or a chamber and an exterior environment or chamber and is designed with such features, including such cross-sectional area transitions between pipes or passages (4, 6, 12, 13) and the chambers (1, 2, 3) that the sound attenuation achieved by the device is high while the pressure drop across the silencer is low and that high attenuation at low characteristic frequencies of flow systems comprising the device are obtained. One or more diffusers (10a, 12a, 13a) for diffusing at least part of the gas flow, e.g., at the inlet to the chambers may be comprised in the device. One or more monolithic bodies or catalyzers may be comprised in the device. Devices with curved or helical passages (FIG.