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 cold air intake system is provided for actively controlling airflow based upon user input and/or demand conditions. Two air inlets are provided into a sealed air box with the secondary air intake including an air control valve for modulating intrusion of intake air. The valve has a valve seat formed the housing sidewall and a flap door valve member actively actuated via a controller. The mass air flow sensor indicates total demand. A pressure sensor and a temperature sensor provide additional input from the airbox. The controller modifies the valve position based upon pressure, temperature and mass air flow. Control is biased to increase secondary air intake when airbox pressure decreases and biased to decrease secondary air intake when airbox temperature increases. Controller biasing occurs between 30 F. to 160 F. and over pressure ranges between 0.01 H.sub.2O to 5 H.sub.2O.

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.

A negative pressure control valve (44) is disposed in a part of an intake passage (12) upstream of a confluence (30) of an EGR passage (27) and the intake passage (12). When in an EGR region (Regr) where an EGR gas is recirculated to the intake passage (12) through the EGR passage (27), the negative pressure control valve (44) is controlled in a manner to ensure a differential pressure between an exhaust passage (13) and the intake passage (12). When in an operation region (R2) lower in load than the EGR region (Regr), the negative pressure control valve (44) is controlled in a closing direction so as to suppress occurrence of noise.

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.

An intake noise reduction device that can mitigate deformation of a flow-regulating net portion made of an elastic body. The intake noise reduction device 100 is made of an elastic body that is disposed downstream of a throttle valve and includes an annular gasket portion 110 and a flow-regulating net portion 120 provided inside the gasket portion 110 integrally with the gasket portion 110, constituted by a linear portion having a mesh shape. The linear portion having the mesh shape constituting the flow-regulating net portion 120 includes first linear parts 121 that extend radially and second linear parts 122 that extend circumferentially. One of any given two parts of the first linear part 121 on a radially outer side has a width larger than or equal to that of the other part on a radially inner side, and a radially outermost part of the first linear part has a larger width than a radially innermost part.

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.

A variable air intake apparatus in accordance with the present invention includes an valve configured to open a through hole formed at a duct body when an engine is driven at a high output to change a path of air introduced into the engine depending on an engine RPM, in which a magnet is mounted on any one of the valve and the duct body and a steel member is mounted on the other one thereof to maintain a state in which the valve closes the through hole, and a buffering member is mounted on any one of the valve and the duct body to prevent generation of hitting sound that is generated when the valve hits the duct body.

A pneumatically insulating and acoustically permeable symposer device for a noise transmission duct of an internal combustion engine; the insulating symposer device comprises: an outer casing, which has an inlet opening and an outlet opening; an actuator plate, which is mounted so as to slide longitudinally; an emitter plate, which is mounted so as to slide longitudinally and is rigidly constrained to the actuator plate; an insulating element, which is arranged between the actuator plate and the emitter plate; and a communication duct with an adjusted cross section, which establishes a limited pneumatic communication between an inlet opening arranged upstream of the actuator plate and an intermediate chamber arranged downstream of the actuator plate, so that the inlet chamber and the intermediate chamber have the same static pressure but do not have the same dynamic pressure.