A sound damping device adapted to be arranged inside a duct, comprises a first element (40a) including at least one first wall (20a) of a first channel (12a) having a first channel inlet (13a) and a first channel outlet (13b), a second element (40b) including at least one second wall (20a) of a second channel (16a) having a second channel inlet (14b) and a second channel outlet (14b), said and outlet regions being substantially opposite to one another, wherein at least a portion of at least one of said first and second elements (40a, 40b) comprises an acoustic energy dissipative sheet material. In accordance with the invention, said first element (40a) comprises a guide means (21) further defining said first channel (12a); said second element (40b) comprises a second guide means (21) further defining said second channel (16a); and said first and second guide means (21) are arranged in relation to one another in such a way that the first channel (12a) forms a first angle in relation to the second channel (16a).

A sound damping device adapted to be arranged inside a duct, comprises a first element (40a) including at least one first wall (20a) of a first channel (12a) having a first channel inlet (13a) and a first channel outlet (13b), a second element (40b) including at least one second wall (20a) of a second channel (16a) having a second channel inlet (14b) and a second channel outlet (14b), said and outlet regions being substantially opposite to one another, wherein at least a portion of at least one of said first and second elements (40a, 40b) comprises an acoustic energy dissipative sheet material. In accordance with the invention, said first element (40a) comprises a guide means (21) further defining said first channel (12a); said second element (40b) comprises a second guide means (21) further defining said second channel (16a); and said first and second guide means (21) are arranged in relation to one another in such a way that the first channel (12a) forms a first angle in relation to the second channel (16a).

An engine muffler apparatus for reducing noise and pollution from small gas engines such as those on landscaping tools includes an outer housing having a central neck extension with a principal aperture extending through to an outer housing cavity. The neck extension is selectively engageable with an exhaust of a small gas engine. The outer housing cavity has a plurality of vent apertures. An intake extension tube and a medial tube are coupled to the outer housing cavity. The medial tube has a medial cavity. A first filtering medium is coupled within the medial cavity and filters pollutants passing therethrough. A second filtering medium is coupled within the outer housing cavity outside of the medial tube and dampens sound waves passing through the apparatus from the exhaust.

A substantially metal-free exhaust subsystem includes an exterior housing formed of polymer; and a pipe formed of a layered fibers formed at least partially of glass, and bound by an inorganic binder. The fibers may be glass or ceramic, and may define micro-pores on the interior of the pipe that aid in absorbing acoustic energy, and thereby attenuating exhaust noise.

A substantially metal-free exhaust subsystem includes an exterior housing formed of polymer; and a pipe formed of a layered fibers formed at least partially of glass, and bound by an inorganic binder. The fibers may be glass or ceramic, and may define micro-pores on the interior of the pipe that aid in absorbing acoustic energy, and thereby attenuating exhaust noise.

There is provided a method for filling a silencer with glass fiber, for filling an internal space between a case and an inner pipe with glass fiber in a silencer in which a porous inner pipe penetrates through a pair of through holes in the case, the method including shifting the inner pipe in a penetrating direction from a normal position where the inner pipe is secured to the case, inserting a nozzle auxiliary portion into an interior of the case from a through hole opened by the inner pipe being shifted, supplying glass fiber into the interior of the case from a nozzle of a glass fiber supply machine connected to the nozzle auxiliary portion, and filling the internal space between the case and the inner pipe with glass fiber.

There is provided a method for filling a silencer with glass fiber, for filling an internal space between a case and an inner pipe with glass fiber in a silencer in which a porous inner pipe penetrates through a pair of through holes in the case, the method including shifting the inner pipe in a penetrating direction from a normal position where the inner pipe is secured to the case, inserting a nozzle auxiliary portion into an interior of the case from a through hole opened by the inner pipe being shifted, supplying glass fiber into the interior of the case from a nozzle of a glass fiber supply machine connected to the nozzle auxiliary portion, and filling the internal space between the case and the inner pipe with glass fiber.

A silencer is equipped with a hollow tubular portion in which a discharge flow passage is formed that communicates on one end side thereof with a discharge port of a fluid pressure device (ejector) through which a pressure fluid is discharged, a cap member attached to another end part of the tubular portion, a sound absorbing member attached to an inner wall surface of the tubular portion, and a plurality of discharge ports adapted to discharge the pressure fluid, which has passed through the discharge flow passage in an axial direction of the tubular portion, in radial directions perpendicular to the axial direction.

A silencer is equipped with a hollow tubular portion in which a discharge flow passage is formed that communicates on one end side thereof with a discharge port of a fluid pressure device (ejector) through which a pressure fluid is discharged, a cap member attached to another end part of the tubular portion, a sound absorbing member attached to an inner wall surface of the tubular portion, and a plurality of discharge ports adapted to discharge the pressure fluid, which has passed through the discharge flow passage in an axial direction of the tubular portion, in radial directions perpendicular to the axial direction.

Devices, systems and methods are described for reducing noise emitted from active aerosol and bioaerosol collection devices. The system includes a noise reducing muffler between the collection component and the air mover and a noise reducing baffle at the outlet of the air mover. The muffler reduces higher frequency noises emitted from the air mover inlet while the baffle reduces lower frequency noises emitted from the air mover outlet. Placement of the muffler between the collection component and the air mover eliminates the potential for loss of particles to the muffler prior to collection.