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.

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 cleaner for an internal combustion engine includes a first housing having an inlet and an upper opening, a second housing having an outlet and a lower opening, a filter element arranged between the upper opening of the first housing and the lower opening of the second housing. The first housing includes a sound reducing wall portion. The sound reducing wall portion has a sound absorbing layer, which is made of nonwoven fabric, and an inner covering layer, which is fixed to the inner surface of the sound absorbing layer and made of a material having a lower air permeability than that of the sound absorbing layer.

The invention relates to an engine air filter unit for a vehicle (1) that is designed to supply filtered air to an internal combustion engine of the vehicle (1). The engine air filter unit (10) comprises a main filter (14), a mounting base (15) to secure the engine air filter unit (10) on at least one body panel (7, 71, 72) of the vehicle, a pre-separator fluidically connected to the main filter. The main filter (14) is arranged on a side of the mounting base (15) and the pre-separator (18) is arranged on the opposite side of the mounting base (15). The pre-separator housing is at least partly formed by the mounting base (15) and an air duct (19) extends through the mounting base (15) to fluidically connect the pre-separator to the filtration chamber.

In an air cleaner, an air cleaner case having an upper opening which opens upward is formed. The air cleaner case is formed of a front wall, a rear fender, and right and left side covers. The upper opening is closed by a seat. A sound absorbing member is bonded to a bottom plate of the seat and housed in an air cleaner space. The intake noise in the air cleaner is absorbed by the sound absorbing member.

A noise reduction apparatus includes a housing, a first baffle component, and a second baffle component. The housing includes a first installation chamber configured to contain diesel generating equipment, and the first installation chamber has a top plate, a bottom plate, and a first side plate, and a second side plate that is disposed opposite the first installation chamber from the first side plate. An air intake vent is disposed on the first side plate, and an air exhaust vent is disposed on the second side plate. A first serpentine channel is formed in the first baffle component, and one end of the first serpentine channel is connected to the air intake vent. A second serpentine channel is formed in the second baffle component, and one end of the second serpentine channel is connected to the air exhaust vent.

A pre-cleaner for an internal combustion engine is arranged in an intake passage of the internal combustion engine at an upstream side of a filter of an air cleaner. The pre-cleaner includes a casing that includes a cylindrical side wall and swirl generation vanes that swirl intake air about an axis of the casing. The side wall has a portion located next to an upstream side of the swirl generation vanes that is formed from an air-permeable fibrous molded body.

An intake duct for an internal combustion engine includes a plurality of segments coupled together into a tubular shape. The segments include at least a first segment and a second segment. The first segment is formed from a material harder than the second segment. The first segment includes a groove that extends in the extending direction in a portion coupled to the second segment and projections that project from one of two inner surfaces of the groove. The second segment is formed from a material that allows for elastic deformation. The second segment includes a rib. The rib extends in the extending direction and has a projection width that is less than the opening width of the groove. The rib is fitted into the groove so that the projections locally compress the rib in the width direction of the groove.

An apparatus for reducing flow noise of an air intake system of a vehicle is provided as an assembly of a body member and a cover member. An acoustic metamaterial unit includes a chamber having a predetermined size, an inlet flow path, and an outlet flow path provided therein and is connected to a pipe of an air intake system. The apparatus advantageously reduces or removes high-frequency flow noise occurring in a turbocharger by using the acoustic metamaterial unit. The size and shape of the acoustic metamaterial unit is standardized such that the acoustic metamaterial unit is used compatibly regardless of the type of vehicles, which can make it possible to advantageously reduce costs and improve salability.

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.