An air duct of an internal combustion engine has an inner pipe providing a flow channel and a housing with a first housing part and a second housing part, wherein the inner pipe is arranged in the housing. The first housing part and the second housing part enclose a chamber between the inner pipe and the housing. The inner pipe has at least one section with perforations in a wall of the inner pipe, wherein the perforations completely penetrate the wall of the inner pipe. A cylindrical acoustic component at least partially encloses the at least one section of the inner pipe at an outer side of the inner pipe. A wall of the cylindrical acoustic component is provided, at least in sections thereof, with continuous openings. The flow channel is acoustically connected via the perforations and via the continuous openings to the chamber.

A muffler assembly including a central common active control valve may include a central body for guiding exhaust gas discharged from an engine to flow in bilateral directions in a branched manner, the central body comprising the active control valve disposed in a flow path of exhaust gas, and a pair of main mufflers, each separately disposed at opposite sides of the central body to exhaust exhaust gas introduced from the central body, in which the flow path and an exhaust path of the exhaust gas may be variable based on opening and closing of the active control valve.

An attenuation device for attenuating sound waves, and a corresponding system and method, generated by a source emitting sound waves having frequencies between f1 and f2 and wherein the pressure levels are between n1 and n2. The attenuation device comprising at least one acoustic absorber comprising at least one non-linear membrane; the attenuation device being configured in such a way that the first face of the absorber is in acoustic communication with the source. The attenuation device also comprises at least one coupling element for coupling the second face with the source, the coupling element being configured to transmit to the second face sound waves according to the sound waves emitted by the source, and of which the phase and/or the amplitude leads to a pressure differential of the sound waves arriving respectively on the first and second face at the same time.

An air conduction part for conducting a compressible medium, which part has a cross section through which the medium passes in a flow direction of the medium when the air conduction part is used, which flow direction approximately corresponds to a longitudinal axis of the air conduction part, the air conduction part including at least one wall arrangement that laterally defines the cross section of the air conduction part and conducts the medium. The wall arrangement are provided with at least one shell and with at least one damping device that removes sound energy from the medium, and the shell and the damping device are integrally interconnected so that, with a justifiable amount of outlay, the resulting air conduction parts effectively damp sound and the transport direction of the medium and/or the cross section of the air conduction part may change.

Provided acoustic devices include an external housing defining an expansion chamber and a wall extending through and partitioning the expansion chamber into a central chamber and a peripheral chamber adjacent the central chamber, wherein an inlet and outlet communicate with the central chamber, and wherein the wall includes a plurality of apertures formed therethrough to allow air movement to and from the central and expansion chambers, the plurality of apertures sized to provide an average flow resistance ranging from 100 MKS Rayls to 5000 MKS Rayls. The acoustic devices advantageously show significant sound attenuation while streamlining air flow to reduce pressure drop across the expansion chamber.

A sound attenuating baffle mounts within the duct section of an air distribution HVAC system, a ventilation system, or other air movement system for either air or gas streams, in which the duct section can be mounted directly to a fan or incorporated into a transmission duct. The sound attenuating baffle is typically oriented in the flow direction through the duct, and includes an outer casing containing sound absorbing material therein. An internal mass layer formed of a sound barrier material is suspended within the sound absorbing material which fills the outer casing. The mass layer increases the low frequency sound attenuation of the sound attenuating baffle.

An exhaust silencer includes a housing defining an interior and a tube disposed in the interior and defining an opening. A gas-flow deflector is configured to heat shield an interior wall of the housing from exhaust gases exiting the opening. The deflector has a deflector plate and a riser. The riser has a first portion connected to the interior wall and a second portion connected to a backside of the deflector plate to suspend the deflector plate in the interior such that the backside is completely spaced from the interior wall to form an insulating airgap therebetween.

A panel is provided for attenuating noise. This panel includes a first skin, a second skin and a core, which forms a plurality of cavities vertically between the first skin and the second skin. The core includes a first wall, a second wall, a first baffle, a second baffle and a first septum. The cavities include a first cavity formed laterally between the first wall and the second wall and longitudinally between the first baffle and the second baffle. The first septum is longitudinally between the first baffle and the second baffle and divides the first cavity into fluidly coupled sub-cavities. The first septum is angularly offset from the first wall by an acute angle. One or more perforations in the first skin are fluidly coupled with the first cavity.

A fan silencer module includes a housing having a first end of the housing, a second end of the housing, and an interior surface between the first end of the housing and the second end of the housing. Acoustic absorbing material is disposed on the interior surface. A honeycomb air flow director is disposed at the second end of the housing. And an electromagnetic interference gasket surrounds an outer edge of the honeycomb air flow director. In an embodiment, a depth of the electromagnetic interference gasket is at least as deep as a depth of the honeycomb air flow director. Also provided is a handle, and a latch actuator, to enable removal and replacement of the fan silencer module and an associated fan module from a chassis.

A sound suppression apparatus for installation inside a gas transport duct is provided. The sound suppression apparatus comprises a resistive sound-absorbing element (110) and a housing providing a reactive sound-attenuating element (130) communicating with a surrounding of the apparatus via opening in an outer surface of the housing. An outer surface of the sound suppression apparatus comprises an outer surface of the resistive sound-absorbing element and the outer surface of the housing. A gas transport duct comprising the sound suppression apparatus is also provided.