An air duct for a vehicle functions to reduce intake noise and includes an outer housing configured having a pipe shape so that outside air is introduced into an engine therethrough. The air duct also has an inner pipe fixed in the outer housing so that an outer surface of the inner pipe is spaced apart from an inner surface of the outer housing, thereby partitioning the inside of the outer housing in a radial direction. A space between the inner pipe and the outer housing communicates with the inside of the inner pipe.

A turbocharger air intake silencer with adjustable cavity space structures is provided. The turbocharger air intake silencer comprises a silencer connecting flange and a first resonator device. The first resonator device comprises a first silencer sealing plate, a first annular sound absorption cavity body, a first rotary table, a first rotary steering gear and a first valve. A first sound absorption cavity is enclosed by the first silencer sealing plate, the first annular sound absorption cavity body, the first valve and the first rotary table. A first sound absorption cavity inlet pipe is arranged beside the first sound absorption cavity. The first sound absorption cavity and the first sound absorption cavity inlet pipe form a Helmholtz resonator. The first rotary steering gear is mounted on the silencer connecting flange. The rotary steering gear is connected with a first rotary rack.

A turbocharger air intake silencer with adjustable cavity space structures is provided. The turbocharger air intake silencer comprises a silencer connecting flange and a first resonator device. The first resonator device comprises a first silencer sealing plate, a first annular sound absorption cavity body, a first rotary table, a first rotary steering gear and a first valve. A first sound absorption cavity is enclosed by the first silencer sealing plate, the first annular sound absorption cavity body, the first valve and the first rotary table. A first sound absorption cavity inlet pipe is arranged beside the first sound absorption cavity. The first sound absorption cavity and the first sound absorption cavity inlet pipe form a Helmholtz resonator. The first rotary steering gear is mounted on the silencer connecting flange. The rotary steering gear is connected with a first rotary rack.

A resonator (1) has at least first and second annular chambers (2, 3, 17) arranged between inlet and outlet pieces (22, 21). An inner pipe (4) extends between the inlet piece (22) and the outlet piece (21) and has wall holes (23) that connect to the annular chambers (2, 3, 17). The first annular chamber (2) has a U-shaped circumferential wall (6) coaxial to the resonator longitudinal axis (5) and transitions at both ends to engage the inner pipe (4). The second annular chamber (3) has an L-shaped circumferential wall (12) coaxial to the resonator longitudinal axis (5). An end of the L-shaped circumferential wall remote from the first annular chamber (2) transitions into a cylindrical end piece (13), and an opposite end of the L-shaped circumferential wall lies on part of the outer wall (9) of the first annular chamber (2) extending parallel to the resonator longitudinal axis (5).

An air cleaner for an internal combustion engine is arranged to reduce intake noise. The air cleaner includes an air cleaner element for cleaning an intake air, and an elastic member for reducing intake noise by utilizing an inside space of the air cleaner. An inside space of the elastic member is in communication with the inside space of the air cleaner through a communication passage. Preferably, a surrounding space formed between the elastic member and a case portion for receiving the elastic member is opened to the outside.

An intake system is for a marine drive. The intake system comprises a throttle device that receives intake air for combustion; an intake conduit that conveys the intake air to the throttle device, wherein the intake conduit has an upstream inlet end, a downstream outlet end, and a radially outer surface that extends from the upstream inlet end to the downstream outlet end; and an intake silencer coupled to the radially outer surface and configured to attenuate sound emanating from the intake system.

An engine intake air duct 1 has an intake portion 10 that extends along a first center line A, and a main duct portion 20 that extends along a second center line B. The main duct portion 20 has a merging portion 50, a discharge opening 21, and an extending portion 40 that extends from the merging portion 50 towards an opposite end to the discharge opening 20. A reflecting wall 41 is provided at an end face of the extending portion 40. The intake portion 10 merges with the main duct portion 20 in such a way that the first center line A is directed towards a downstream end of the main duct portion 20.

A variable noise attenuation element includes at least two tube sections that define an overall tube length that defines a first effective length and associated first peak frequency for noise attenuation, and a valve having a valve member. The valve joins the tube sections together and includes openings that permit communication between the tube sections when the valve is in an open configuration. The valve member operates to close the opening in response to a predetermined vacuum level within the tube sections to define a second tube effective length and associated second peak frequency for attenuation that is less than the overall length. A method of attenuating noise in a vehicle using a passive attenuation arrangement operates a valve disposed between two tube sections to change an effective length of the tube and associated peak frequencies for attenuation in response to an engine operating parameter.

A variable noise attenuation element includes at least two tube sections that define an overall tube length that defines a first effective length and associated first peak frequency for noise attenuation, and a valve having a valve member. The valve joins the tube sections together and includes openings that permit communication between the tube sections when the valve is in an open configuration. The valve member operates to close the opening in response to a predetermined vacuum level within the tube sections to define a second tube effective length and associated second peak frequency for attenuation that is less than the overall length. A method of attenuating noise in a vehicle using a passive attenuation arrangement operates a valve disposed between two tube sections to change an effective length of the tube and associated peak frequencies for attenuation in response to an engine operating parameter.

A variable intake system includes a pair of surge tanks connected in a communicating manner to a main intake pipe through a low speed communication pipe and a high speed communication pipe, a middle speed communication pipe for connecting the pair of surge tanks, and a noise reducing member integrally provided at the middle speed communication pipe to reduce noise.