Abstract: A process is provided for filling a muffler with fibrous material as well as a muffler filled with fibrous material. The process includes a first step of providing a muffler comprising a closed outer shell having an inner cavity and a perforated pipe. The perforated pipe has a first end portion with at least one fill opening. A second step comprises feeding fibrous material into the outer shell inner cavity through the at least one fill opening in the perforated pipe to form a fibrous product in the outer shell.

Abstract: An insert assembly for a muffler of a high-performance motor cycle, having an insert with a filling of compressed heat-resistant, sound-absorbing material mounted on a removable hollow tube having an inside diameter greater than the outside diameter of the perforated core of the muffler. The filling includes a bulked-up continuous filamentary material. Once the insert has been introduced into the muffler by sliding the tube along the core, the tube is then withdrawn leaving the insert behind in the muffler. Removal of the tube allows the filling to relax towards its intended density. The first subsequent exposure to hot exhaust gases causes certain portions of the insert to degrade, allowing further relaxation of the filling to assume its intended density. Further, the tube precludes potential damage to the insert during its introduction into the muffler.

Abstract: In order to provide a sound absorbing material superior in acid resistance, alkali resistance and sound absorbing quality and a sound absorbing layer using this sound absorbing material, multiple pieces of basalt yarn obtained by dissolving basalt to be continuous fibers are bundled by a fiber bundling agent to acquire a bundled material, and the bundled material is fibrillated to obtain a bulky sound absorbing material. Moreover, the sound absorbing material is arranged on the outer periphery of a perforated pipe constituting a muffler to form a sound absorbing layer.

Abstract: An exhaust pipe for motor vehicle muffler having a plurality of muffling holes arranged over the periphery, a partially perforated conical tube suspended on the inside and axially extended from the exhaust gas input end thereof for accelerating exhaust gas passing through, and a plurality of spiral portions formed integal with the periphery thereof and spaced around the conical tube for turning exhaust gas escaped from peripheral through holes on the conical tube into a spiral flow.

Abstract: A sound-absorbing duct structure for an intake system of an automotive internal combustion engine. The sound-absorbing duct structure comprises a duct defining thereinside a gas passage. A part of the duct is formed with a plurality of small holes. An expanded duct section is formed around the part of the duct. The expanded duct section defines therein an inside space which is in communication with the gas passage through the small holes. The inside space has a cross-sectional area larger than that of the gas passage. A sound-absorbing section is disposed in at least a part of the inside space of the first expanded duct section. The sound absorbing section includes a piezoelectric material exhibiting a piezoelectric effect, and an electrically conductive material in contact with the piezoelectric material.

Abstract: A silencer assembly having a cylindrical chamber having a closed cylindrical outer wall, a first end wall and a second end wall, the first end wall having an inlet therein, and the second end wall having an outlet therein, an internal annular chamber proximate the cylindrical outer wall, the internal annular chamber bounded by the cylindrical outer wall and by a perforated cylindrical inner wall, the internal annular chamber containing single strand fiberglass acoustic fill material, the internal annular chamber having no internal barriers therein, and, a perforated generally cylindrically shaped core located inside of the cylindrical chamber positioned in spaced relation to the internal annular chamber and also in spaced relation to the inlet and outlet, creating a generally annular shaped passageway for exhaust gas, the core containing single strand fiberglass acoustic fill material.

Abstract: A pulsation damper including an inlet, an outlet and a silencing member is disclosed. At least one of the inlet and the outlet is provided with a diffuser including a tubular member provided with a plurality of first openings, a plurality of second openings and reinforcement bodies extending around the tubular member. At least one of the second openings is covered by a plate having the first openings, smaller than the second openings therein.

Abstract: A double-walled-structure, such as a silencer for use in a ventilation duct system, has a perforated inner tube, an outer casing which is arranged at a distance from the inner tube and encloses the same, and a tubular, sound-absorbing element which is arranged between the inner tube and the casing. The tubular element has an increasing density radially outwards from the center axis of the inner tube. The silencer is produced by the sound-absorbing element being arranged on the inner tube, and the inner tube with the sound-absorbing element arranged thereon being enclosed in the surrounding outer casing.

Abstract: This invention provides preforms of continuous glass fiber strands for use as the sound absorbing material in an engine exhaust muffler. Preferably, the material is made of glass fibers of E glass compositions. With this invention, the strands are fluffed up, not directly in the muffler, but in a cavity that is made of a perforated shell matching the muffler shape. During this operation, a powder binder also is blown in with the fibers. This blowing operation is completed by forcing hot air through the preform which melts or cures the binder and allows it to bond the fibers together.

Abstract: An exhaust tube of the rear of an automobile includes a muffler tube and an outer tube. The muffler tube is provided with a plurality of holes in a central area therof. One end of the muffler tube is provided with a concave annular trough and further provided with a convex edge. One end of the outer tube is received within the concave annular trough when the muffler tube is combined with the outer tube. In addition, the inner side of outer tube near the end edge is engaged against the convex edge of the muffler tube.

Abstract: In order to create a process for producing muffler inserts as well as novel muffler inserts, which are most optimally adaptable in size and shape to the interior space of the muffler housing to be filled, by simple means, and which also can be produced economically and have improved effect, a process is proposed for producing muffler inserts which operate entirely or partially according to the absorption principle, whereby a predetermined amount of a loose bundle of individual elements of a suitable sound-absorbing material is formed, the loose bundle is shaped roughly in an assembly shaping unit corresponding to the intended shape of the muffler insert, and whereby the loose bundle is fixed into a shaped composite in the shape corresponding to the assembly shaping unit, in such a way that the fixed shape can be handled without individual elements loosening until assembly for the specified uses of the muffler insert; however during the specific use as a muffler insert the fixing is at least partially released

Abstract: A silencer for a vehicle exhaust assembly is described. The silencer comprises an outer wall, a porous exhaust pipe which defines an inner wall and a sound absorbent fibrous material located between the inner and the outer wall. The sound absorbent fibrous material is substantially unidirectional and parallel with the direction of gas flow through the porous exhaust pipe. The fibre is enclosed in a silencer cartridge. A method of producing such a cartridge is also described.

Abstract: A method of reducing noise in a barking plant; a barking drum, a chipper and a conveyor between these. The penetration of noise through conveying openings of a partly or wholly covered conveyor (3) for receiving logs from a barking drum (1), and/or a partly or wholly covered conveyor (8′) for feeding logs to a chipper (11), is reduced, and the noise level is decreased by means of the water (21) used for washing the logs. The water forms a continuous curtain (18, 19) at the front and/or back end of the conveyor (3, 8, 8′) between the drum (1) and the chipper (11).

Abstract: A device and a method for achieving sound reduction within a frequency band in a transport system for gaseous medium, the transport system being arranged between an inlet, which is connected to a sound source, and an outlet. The transport system comprises with a plurality of interconnected channel parts (1-7) and exhibits at least one module (8, 9) comprising at least one reflection attenuator (4) with a resistive length (a2, b2) and at least one reactive attenuator (3) with a reactive length (a1, a3, b1, b3). The resistive length is brought to constitute a quarter of a wavelength of the center frequency of the frequency band and the reactive length is brought to constitute a quarter of a wavelength of a frequency between, respectively, the lower and upper limit frequencies of the frequency band.

Abstract: A silencer for reducing acoustic energy in an exhaust stream of gases from a combustion type source, particularly turbo-generators. In a preferred embodiment, the silencer includes an outer housing having at least one outlet opening and an inner housing provided at least partially within the outer housing. The inner housing has at least one inlet opening for receiving the exhaust stream along a flow axis and the inlet opening is in fluid communication with the outlet opening. The inner housing further includes an acoustic energy interface surface having acoustic absorbing elements oriented in a substantially non-normal direction to the flow axis. Sound absorbing material is preferably contained between the outer housing and the inner housing. In this way, the gas flow is effectively separated from the acoustic energy without significantly increasing the back pressure or resistance to flow of the exhaust stream.

Abstract: The present invention provides for noise reduction during operation of a portable blower by reducing the noise or acoustic energy escaping from the housing outlet and blower tube. The noise reduction is achieved by placing sound absorbing material in the blower tube. The sound absorbing material may include flared upstream and downstream ends to reduce turbulence. The sound absorbing material may be held within the blower tube by an insert frame such that substantial portions of the sound absorbing material are exposed to air passing through the blower tube. Also disclosed is a sound absorbing insert that can be placed within an existing blower tube to retrofit portable blowers with noise reduction technology.

Abstract: A silencing member has a plurality of elongate members each having a plurality of elongate glass fibers, with the plurality of elongate members being cross-layered to define a fabric.

Abstract: Method for filling cavities in workpieces or semi-finished products is provided, in which thermally foamable powdered carbon is added in fixed locations into the cavity to be filled and is heated together with the workpiece or semi-finished product in such fashion that the powdered carbon swells and fills the cavity as carbon foam, with the particles of powdered carbon in the delivered state being smaller than after foaming. A structural component is formed, especially a workpiece or semi-finished product for mounting on or in a motor vehicle body, having an enclosed chamber in which thermally foamable powdered carbon is added in a fixed location, with the powdered carbon being heated together with the structural element to swell the powdered carbon and form carbon foam.

Abstract: A silencer and method of making are described. A tube is wrapped with a layer of texturized fiber yarn. A septum is then overlaid. Other layers of fiber and septums may also be added. Once rolling is completed, the roll is placed in a canister with end caps.

Abstract: A free-standing, compressed, hardened porous, resilient sheath of sound absorbing fibrous material for use in silencer or muffler pipes as the intermediate sound absorbing element between the inner perforated and outer sleeve elements of a three-element pipe is formed by (a) wrapping an uncompressed pad of fibrous material containing a thermo-setting hardening agent around a shaped mandrel having outside surface shape and dimensions conforming the outside surface shape and dimensions of the inner three-element muffler pipe, (b) subjecting the wrapped mandrel and sheath of uncompressed material to a pressure sufficient to conform the outside surface of the compressed pad to the inside surface shape and dimensions of the outer muffler pipe sleeve element, and to a temperature sufficient to set the thermo-setting hardening agent; and (c) removing the mandrel.

Abstract: Silencer for gas discharge device employing easily replaceable cartridge utilizing juxtapositioned layers of wire mesh and porous resilient material which dissipate the energy stored in an exhaust system and deflect under pressure of the exhaust gases to provide a self cleaning function and a cylindrical liner mounted within the cartridge comprising the same or larger wire mesh and wire diameter size than used in the cartridge for capturing the large particles of the exhaust gases before they pass through the layers of wire mesh forming the cartridge.

Abstract: The invention provides a muffler for an internal combustion engine having excellent durability (resistance to scattering) even when being exposed to a high-temperature exhaust gas and capable of maintaining a high sound absorption coefficient over a long period. Such a muffler comprises a metal tube provided with a plurality of small holes, an inorganic fiber sound-absorbing material arranged on the outer periphery thereof and a metal shell covering the outside of the sound-absorbing material, in which a scattering prevention member is disposed between the metal tube and the sound-absorbing material. The sound-absorbing material is a laminated structure of crystalline alumna fiber mat and glass fiber mat. As the scattering prevention member, there is used a stainless woven wire cloth, a woven fabric made from inorganic fiber and a metal roll.

Abstract: The present invention is a noise reduction apparatus for use in the exhaust system of an internal combustion engine which absorbs acoustical energy from the pressurized exhaust gases while minimizing restrictions on the exhaust gases as they flow therethrough. The relatively unrestricted exhaust gas flow provided by the present invention significantly reduces the build up of back pressure and the associated drop in power and performance of the engine. At the same time, by absorbing acoustical energy from the exhaust gases, the noise level of the exhaust system is reduced. The present noise reduction apparatus includes a housing operatively adapted for being disposed in the exhaust system of an internal combustion engine, and a plurality of sound absorbing layers disposed inside the housing. Each layer is operatively adapted to allow exhaust gases to flow therethrough while absorbing acoustical energy from exhaust gases coming in contact with the layer.

Abstract: A muffler device for the exhaust of an internal combustion engine comprising a tube (1) formed of at least a cone and a cylinder of a single piece of perforated sheet metal with alternating holes of varying diameters distributed over its length, the tube (1) being surrounded with a coaxial envelope formed of a cylindrical and/or conical front portion (2) and a back portion (3) with a conical nozzle terminating in an exhaust pipe at an angle to permit exhaustion of gas, the exhaust gases passing through an annular space between the tube and envelope through outlet parts or walls whose form and geometry prevent the formation of a turbulence generating back pressure.

Abstract: A muffler assembly (10) for use with internal combustion engines discharging hot exhaust gases. The muffler assembly includes an elongated casing (15) having an inlet opening (12) at one end and an outlet opening (13) at an opposite end. A sound attenuating partition assembly including a conically converging, perforated, dispersion shell (33) and a transverse wall (45) are provided inside the muffler casing (15). The dispersion shell (33) tapers inwardly by an amount resulting a cross sectional area (A.sub.3) between the dispersion shell (33) and casing (15) at the transverse wall (45) which is at least equal to the area (A.sub.1) of the inlet opening (.sub.12). The combined area (A.sub.4) of the perforations (46) in the dispersion shell (33) upstream of the transverse wall (45) also is at least about equal to the area (A.sub.1) of the inlet opening (12). A perforated retaining shell (17) is provided positioned internally of the casing radially outwardly of the dispersion shell (33).

Abstract: An engine muffler and spark arrester includes an oval shaped outer tube extending along an axis and having an inlet end and an outlet end. A plurality of substantially identical nested oval shaped disks are disposed coaxially adjacent the outlet end. Each of the disks has an oval shaped centrally located aperture. An inner tube is disposed coaxially within the outer tube. The inner tube has a circular inlet end and an oval-shaped outlet end. An oval end cap is disposed adjacent the disks. A sound absorbent material can be disposed in a cavity defined between the inner tube and the outer tube. An oval-shaped inlet cap is secured to the inlet end of the outer tube with the inlet cap having a circular centrally located aperture extending therethrough. An oval-shaped outlet cap is secured to the outlet end of the outer tube. The outlet cap has an oval-shaped centrally located aperture extending therethrough.

Abstract: A method of forming and attaching a silencer to a blower pipe involves a silencer that has an inner pipe with many silencer holes and a sound absorption material extending longitudinally around its outer periphery. The blower pipe may be connected to a blower so that a high speed air stream passe through an interior of the inner pipe. The method has the steps of forming the inner pipe by resilient deformation of a flexible member (such as a pair of thin plates or a helically-formed flexible strip) that has a stress-free length preventing it from inserted into the blower pipe without first being deformed. Then, the resiliently-deformed flexible member is introduced into the blower pipe, and the silencer is attached to the blower pipe using a resilient restoring force that was caused by the resilient deformation.

Abstract: Outlet piece for a compressor, which outlet piece contains a damping body (3) applied symmetrically around a passage (2), wherein the passage has a constant diameter and in that the damping body (3) has a transverse dimension which gradually increases along the direction of flow (V), so that this damping body (3) has a transverse thickness which increases along the direction of flow (V).

Abstract: In a method of producing a double-walled structure, such as a silencer for use in a ventilation duct system, use is made of an arrangement having a forming head for forming helically-wound lock-seam tubing. In the forming head, a perforated metal strip is helically would together with an air-permeable cloth strip such that the tubing fed out of the forming head has an outer cover of said cloth. The tube assembly consisting of the perforated tube and the cloth cover is provided with an outer tubular layer of insulating material and then inserted in a casing which makes the silencer complete.

Abstract: A sound absorption structure which is mainly applied to an intake system of an automotive engine for suppressing noise level. The sound absorption structure comprises a base duct portion, and an extended duct portion in which a sound absorption material is installed, and a Helmholtz resonator. The extended duct portion is formed such that a representative diameter of the extended duct portion is greater than that of the base duct portion while connected to the base duct portion. The Helmholtz resonator is set to be resonant at a frequency corresponding to a frequency range of a resonance generated by the installation of the extended duct portion including the sound absorption material. The Helmholtz resonator is integrally formed with the extended duct portion. Therefore, the sound absorption structure ensures an excellent sound absorption ability in the whole frequency range.

Abstract: A fluid guiding element for blocking and damping noises propagating in it has a main passage composed of a flexible inner hose jacket which is resistant to mechanical, chemical or calloric load by a fluid to be guided through the fluid guiding element, an outer hose jacket, and a material insert arranged between the hose jackets and composed of a flexible material which is resistant at least to calloric loads, the main passage having a fluid inlet and a fluid outlet and being provided with at least one turn of substantially 360 between the fluid inlet and the fluid outlet, and at least one auxiliary passage arranged in a cross-section of the main passage and having sound-soft walls, the at least one auxiliary passage being composed of an inner hose jacket, an outer hose jacket and a material insert arranged between the inner and outer hose jackets, the auxiliary passage being provided with at least one turn of substantially 360.degree..

Abstract: A vehicle exhaust device including a rear silencer disposed at the rear portion of a vehicle, a large-capacity silencer having a capacity larger than that of the rear silencer and disposed below a passenger compartment of the vehicle, and an intermediate silencer disposed substantially at the middle of an exhaust tube interconnecting the rear silencer and the large-capacity silencer. With the vehicle exhaust device thus arranged, exhaust noises can be attenuated at a position near an engine forming a noise source, i.e., at the early stage of transmission and with substantially reduced length-dependent resonance of the exhaust tube.

Abstract: A muffler including fiberglass packing is assembled and suitable for use in a closed refrigeration system by avoiding the generation of fiberglass debris and preventing its entry into the fluid path. A perforate tube is serially overlain by a heat resistant fabric covering, a fiberglass packing and a circumferentially adjustable and collapsible sleeve which are inserted as a subassembly into the shell of a pressure vessel.

Abstract: The present invention is a noise reduction apparatus for use in the exhaust system of an internal combustion engine which absorbs acoustical energy from the pressurized exhaust gases while minimizing restrictions on the exhaust gases as they flow therethrough. The relatively unrestricted exhaust gas flow provided by the present invention significantly reduces the build up of back pressure and the associated drop in power and performance of the engine. At the same time, by absorbing acoustical energy from the exhaust gases, the noise level of the exhaust system is reduced. The present noise reduction apparatus includes a housing operatively adapted for being disposed in the exhaust system of an internal combustion engine, and a plurality of generally concentric and radially spaced tubular sections disposed inside of the housing. Each tubular section is adapted with a porous wall which allows exhaust gases to flow therethrough. A plurality of sound absorbing layers are also disposed inside the housing.

Abstract: An inlet or exhaust line for a reciprocating machine attenuates the sound level of the machine while being simple and economical to produce. A sensor measures the instantaneous flow rate of gases passing through the line while a restriction device variably restricts the cross-section of the line as a function of the instantaneous flow rate measured by the sensor. Material for absorbing acoustic energy covers the internal wall of the line.

Abstract: The invention comprises an exhaust system for a motorcycle engine which has an outer imperforate casing having a substantially elliptical cross-section and an inner, coaxial, perforate sleeve also of elliptical cross-section which is of lesser dimensions to provide an annulus within the casing which is packed with a gas permeable material, high temperature resistant material such as fiberglass. The muffler has a single piece inlet end cap and a single piece outlet end cap. Each end cap has an elliptical flange over which is received an end of the outer casing of the muffler. The end caps also have integral mounting flanges to receive and support the inner perforate sleeve. Preferably the muffler is provided with a replaceable sound choke which is a small diameter sleeve that can be removably secured in the discharge end of the muffler, thereby permitting the muffler to be switched between restricted off-road use and unrestricted off-road use.

Abstract: A silencer assembly is disclosed having at least one expansion section (20,30), tapering outwardly along the length thereof, and a silencing section (40) including a transversing bank of a plurality of parallel acoustical modules (60). Each module (60) has side walls (67) and a front and rear framing member (63,64) with a plurality of longitudinal perforated (74) internal channel member (70) surrounded by an acoustical media (80) therein.

Abstract: Method and apparatus for reduction of fluid borne noise in a hydraulic system are disclosed. An improved isolating hose assembly comprising first and second volumetrically compliant members with an inductive flow member providing fluidic coupling therebetween is disclosed. The improved isolating hose assembly acts similarly to an electronic low pass filter network in deterring fluid borne noise from entering portions of the hydraulic system located therebeyond. In addition, a sound barrier comprising a heavy-walled boot surrounding the first volumetrically compliant member is disclosed. The heavy-walled boot surrounding the first volumetrically compliant member acts to prevent acoustic sound sourced at the wall surface thereof from entering the surrounding atmosphere.

Abstract: In an exhaust gas system for an internal combustion engine for a vehicle which includes an exhaust gas conduit with an exhaust gas cleaner and a silencer, the structure-borne noise emission is reduced by coating surface areas of the exhaust system with a silencing layer consisting of metal powder which is applied by plasma spraying or sintering.

Abstract: Combined air duct apparatus and silencer for attachment to both the inlet and the outlet of a fan unit for a building wherein each silencing apparatus has an exterior housing with an air inlet and an air outlet, one of which is adapted for connection to the fan unit. The inlet and outlet are connected by an airflow passageway defined by interior walls of the housing. A resonator chamber for reducing noise created by the fan unit extends around or is adjacent to the inlet or the outlet that is connected to the fan unit. The chamber is enclosed by chamber walls including a peripheral wall perforated with a number of holes and facing the airflow passageway. First and second series of splitters are also provided with those in each series being spaced apart to form smaller air passageways and mounted side-by-side in a row. The second series is positioned downstream of the first series. In the outlet duct unit, the air inlet is preferably circular while the outlet is rectangular.

Abstract: A muffler for use on the exhaust system of the motor vehicle. The muffler has a central pipe which is surrounded by an outer pipe which leaves an annular space between the two. The outer pipe is open at both ends and the annular space is filled with a sound deadening material. The central pipe has openings which pass to the annular space and a perforated sound deadening member is affixed to the inner surface of the central pipe. Preferably, the outer pipe is outwardly flared at its upstream end, and the perforated sound deadening member is conical in shape.

Abstract: A sound absorbing muffler used to attenuate noise carried by the exhaust gases of an internal combustion engine includes a straight-through flow tube of constant diameter and cross-section. The muffler utilizes both reactive and dissipative components and includes two annular sound absorbing end chambers, an outer annular resonating chamber, and an inner sound absorbing means. The muffler's configuration produces effective noise attenuation, yet low backpressure.

Abstract: An apparatus for modifying an exhaust stream of a diesel engine is provided. The apparatus includes a muffler arrangement having an exhaust inlet and an exhaust outlet in construct and arrange for sound attenuation therein. The apparatus also includes a catalytic converter arrangement positioned within the muffler arrangement between the exhaust inlet and exhaust outlet. During operation, the exhaust flow is directed both through the muffler arrangement and the catalytic converter arrangement, to advantage.

Abstract: A sound absorbing muffler used to attenuate noise carried by the exhaust gases of an internal combustion engine includes a straight-through flow tube of cross-section having no baffles or flow reversals. The muffler utilizes both reactive and dissipative components and includes an outer annular resonating chamber and an inner sound absorbing chamber. The muffler's configuration produces effective broad band noise attenuation even at lower frequencies, yet low backpressure.

Abstract: An exhaust muffler for an internal combustion engine including an outer shell containing two halves made of synthetic resin material, a metallic inner pipe extending through the parting plane between the two halves via a tubular extension extending integrally from the two halves, and an outer sleeve which is fitted onto the tubular extension, preferably by using a bayonet mount structure, for securely joining the two halves at its one end and forming an air-tight seal in cooperation with the part of the inner pipe extending out of the tubular extension at its other end. An arrangement is provided for accommodating a relative displacement between the other end of the outer sleeve and the inner pipe for avoiding the generation of thermal stress due to the difference in the coefficient of thermal expansion between the outer shell and the inner pipe made of different materials.

Abstract: A motor vehicle muffler comprising a housing comprising two half shells, and an exhaust conduit having two ends. The conduit is disposed within the housing and is securely joined to the housing at its two ends. Filler material within the housing surrounds the exhaust conduit, the exhaust conduit being in contact only with the filler material between the two ends of the exhaust conduit. The housing has a length and a width and a depth, its length and width being greater than its depth, and at least one plate extends in the direction of the depth of the housing, between the half shells, and is securely joined to the half shells without touching the exhaust conduit. For this purpose, the plate has notches in which leg portions of the exhaust conduit are disposed in spaced relation to the plate. The half shells of the housing are joined to each other by a folded seam and are joined to the ends of the exhaust conduit by welded joints, and are also joined to the plate by welded joints.

Abstract: A muffler is provided for sound dampening of wet exhaust gases. The muffler comprises a canister, or housing, having an inlet and an outlet. The housing is preferably constructed of a plurality of resealable interlocking sections which can be disengaged from one another to allow opening and closing of the housing to permit exposure of the sound dampening element(s) for inspection and replacement thereof or to allow for removal, servicing and replacement of the sound dampening element(s) which are positioned therein. The sound dampening element(s) can be formed from a foamed, heat resistant moldable material, such as a closed-cell concrete.

Abstract: In an automobile, a silencer connected to an exhaust pipe includes a casing made of thermally resistant synthetic resin and provided at an inner surface with a thermally insulating material. The silencer is disposed between a side frame and a side body and covered with an undercover from below the silencer and is disposed between a side frame and a side body of an automatic vehicle in a space behind a rear wheel.

Abstract: The invention concerns a reactive sound attenuator for air-conditioning ducts, in particular for air ducts in paper mills. The sound attenuator includes at least two chambers separated from another by means of a partition wall. The partition wall is provided with an opening or with a tube placed in the direction of flow of the air flowing through the sound attenuator, the air flowing through said opening or tube out of one chamber into the other. The main plane of the partition wall is at an acute angle in relation to the direction of air flow through the sound attenuator. Preferably, the partition wall is at an angle .alpha. from about 40.degree. to about 70.degree. in relation to the direction of air flow through the sound attention.

Abstract: A car silencer includes an outer pipe having a front expansion chamber defined in a front portion of the outer pipe connected with a connecting tube which is connected to an engine manifold for directing waste gas as discharged from a car engine, an inner pipe detachably inserted in a rear expansion chamber in the outer pipe at a rear portion of the front expansion chamber, an absorbing and filtering medium filled in the inner pipe, and a perforated tail pipe inserted in the absorbing and filtering medium, wherein an engine exhaust gas will be reduced its sound in the front and rear expansion chambers and a plurality of pollutants laden in the exhaust gas will be absorbed, filtered and removed in the absorbing and filtering medium for preventing air pollution caused by an engine waste gas.