Abstract: A side branch resonator for attenuating sound waves of first and second frequencies, the side branch resonator comprising a discharge branch; a resonator branch; an inlet branch flow connected to the discharge branch having an axis, the resonator branch having a wall which defines a resonator branch interior; the resonator branch having an open resonator branch end and a closed resonator branch end; the resonator further comprising an attenuation member for attenuating the first frequency sound waves. The attenuation member is located in the resonator branch interior a first distance from the axis and upstream from the resonator branch closed end. The closed resonator branch end is located a second distance from the axis to provide attenuation of the second frequency sound waves.

Abstract: The improved high performance muffler is used to attenuate the sound waves in exhaust gases from internal combustion engines and the like and has a casing, which includes a closed volume defined by side walls, a top wall, a bottom wall and inlet and outlet end caps. The casing also has a defined exhaust gas-flow passageway, which extends between the end caps, which is bounded by upper and lower walls within the casing and the side walls, and which includes inlet and outlet chambers adjacent to the inlet and outlet end caps, respectively. Two spaced apart, gas-flow channels. A gas-flow director assembly, disposed between the side walls and the upper and lower walls, defines two spaced apart gas-flow channels. The gas-flow channels have a uniform, smooth cross-section, and their lengths are substantially equal.

Abstract: An expansion chamber for the exhaust system of two cycle engines. The expansion chamber includes a diverging section and a converging section. The diverging section has a continually increasing cross-sectional area. A terminal section is integrally attached to the diverging section. A reflective cone is disposed within the terminal section and secured thereto. The converging section is defined by the area contained between the terminal section and the reflective cone. Devices are also provide for directing exhaust gases into and out of the expansion chamber. The reflective cone may be positioned entirely within the diverging section or anywhere between the diverging section and the terminal section, depending on specific performance characteristics desired. The reflective cone may also be secure in various ways depending on its placement.

Abstract: An exhaust system includes an exhaust pipe attached to the engine. Attached to the exhaust pipe is a muffler which has an exhaust gas inlet, a plurality of expansion chambers through which exhaust gas flows, and at least one wall between adjacent expansion chambers. There is an opening or orifice in the wall between adjacent expansion chambers. A flap which covers the orifice or the opening in the wall between adjacent expansion chambers. The flap opens in response to a pressurized surge of exhaust gas entering into the expansion chamber. The muffler also has an exhaust gas outlet for allowing exhaust gas to pass from the second chamber of the muffler. The exhaust system typically has a plurality of chambers attached to one another such that the exhaust gas travels along a tortuous path between the exhaust gas inlet and the exhaust gas outlet. The flap is pivotally attached to the wall between adjacent expansion chambers. The flap is also positioned so that it closes due to gravitational forces.

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: An exhaust muffler includes a housing having a rectangularly shaped hollow interior without fiberglass or other packing. An inlet tube and a first outlet tube extend through one side wall of the housing, and a second outlet tube extends through an opposite side wall. The inlet tube extends to an inner end disposed at a central region of the interior in a position facing away from a forward end wall of the housing toward an opposite rearward end wall, while a baffle assembly within the interior includes perforated partitions that define two Helmholtz chambers, as well as a first passageway from the inner end of the inlet tube to the first outlet tube and a second passageway from the inner end of the inlet tube to the second outlet tube. The baffle assembly includes first and second plates disposed within the first and second passageways to split the flow of exhaust gases.

Abstract: An exhaust muffler includes a housing having a rectangularly shaped interior without fiberglass or other packing, an inlet tube on a first end portion of the housing for conveying exhaust gases to the interior, an outlet tube on an opposite second end portion of the housing for conveying the exhaust gases from the interior, and a baffle assembly within the interior for defining multiple different paths for exhaust gases to follow and two Helmholtz chambers for the exhaust gases to encounter as the exhaust gases flow through the interior of the housing from the inlet tube to the outlet tube. A central chamber flow path is provided that inhibits reverse flow.

Abstract: In the exhaust fluid path, there are provided a porous pipe that is in communication with a muffling chamber via a plurality of small through-holes formed across a wall thickness of the pipe, and an inner pipe of a given length is inserted in the porous pipe with a gap formed between the outer surface of the inner pipe and the inner surface of the porous pipe. The gap is narrowed or closed in its outlet portion and thus the exhaust sound waves flowing through the gap are compressed so that interference and scattering into the muffling chamber of the exhaust sound waves via the small through-holes are promoted, thereby enhancing muffling performance. A plurality of small through-holes may also be formed in the inner pipe. A relatively large opening may be formed in part of the porous pipe to open into the muffling chamber, or a relatively large space may be formed which divides the porous pipe into two pipe elements and opens into the muffling chamber.

Abstract: A resonator type silencer used in the air intake duct of an intake system of an internal combustion engine comprises a first case member which includes a generally cup-shaped section. A pipe section is integral with the cup-shaped section and extends through a bottom wall of the cup-shaped section. The pipe section has an inside portion located inside the cup-shaped section. An axially extending slit is formed in the inside portion of the pipe section. First and second flange portions are integral with the pipe section inside portion and located at opposite sides of the slit. The first and second flange portions are integral with the cup-shaped section bottom wall and located parallel with each other. The pipe section inside portion and the flange portions constitute an integral body having a first end face located near an open end of the cup-shaped section.

Abstract: A muffler including an offshoot path, one end of which is connected to a middle of a ventilation path so as to diverge from the ventilation path, and another end of which is closed. One portion of the offshoot path and another portion thereof are communicated through a communicating portion. Accordingly, sound waves entering the offshoot path are propagated in a direction of a closed portion, and are also propagated via the communicating portion from the one portion to the other portion.

Abstract: An improved aircraft muffler and the method of making it is disclosed. It is a plug muffler design having an outer housing and an internal exhaust conduit. The exhaust conduit has a center partition that blocks the flow of exhaust gas through the conduit. A number of holes are formed through the conduit wall such that the exhaust gas passes out through the holes on the inlet side of the partition and reenter the conduit on the outlet side of the partition. Unlike previous designs, the holes formed in the exhaust tube of the muffler are not flat and do not have hoods. Rather they have formed surfaces that slope. The formed surfaces both protrude above and below the exhaust tube wall. Thus the formed surface creates a directional flow path for the airflow to help increase the velocity, which consequently helps to move exhaust gases through the baffle as opposed to straight holes. The indented holes serve another purpose.

Abstract: A resonator type silencer installed in an intake system of an automotive internal combustion engine. The resonator type silencer comprises a generally cup-shaped base member integrally connected with an air duct through which intake air to be inducted into the engine passes. The air duct is formed with an opening through which the inside of the base member is in communication with the inside of the air duct. The base member is formed at its opened end with a peripheral flange. A cover member is formed at its opened end with a peripheral flange which is bonded to the peripheral flange of the base member to define a sealed chamber. A partition plate is fixedly disposed inside the sealed chamber to divide the sealed chamber into a first resonance chamber defined by the base member, and a second resonance chamber defined by the cover member.

Abstract: An exhaust muffler for mounting on the transom of a powerboat in association with the exhaust pipes which extend through the transom. The muffler comprises a housing extending laterally across the stern of the boat and rearwardly from the transom to define an interior space. The housing has a floor located below the water line; opposed end walls; a front wall located adjacent to the transom with openings formed therein, through which exhaust gas can pass from the exhaust pipes; a rear wall having exhaust ports formed therein and a cover that encloses the interior space. Located within the enclosed space are muffler inserts secured to the floor and also to the front and rear walls. Each insert has a domed portion defining a muffling chamber that communicates with the respective exhaust pipe, and a second domed chamber defining an expansion chamber that communicates with the respective exhaust port located in the rear wall of the housing.

Abstract: Muffler assembly for an engine comprises an outer cylinder constituting a muffler body, an inner cylinder coaxially disposed in the outer cylinder, a connection cylinder disposed inside the inner cylinder having one end on an upstream side and another end on a downstream side, a partition plate disposed inside the inner cylinder at the downstream end of the connection cylinder, first and second silencer chambers formed at the upstream and the downstream end of the connection cylinder, respectively, an inlet, pipe through which an engine exhaust gas is introduced into the muffler body, and an outlet pipe having an upstream end disposed inside the inner cylinder and a downstream end opened outward of the muffler assembly. The connection cylinder has an upstream end portion in which a plurality of holes are circumferentially formed.

Abstract: A muffler assembly of an internal combustion engine comprises an inner casing in which is defined a first expansion chamber into which is inserted one end of the exhaust pipe having another end connected to an exhaust gas port of the engine, an outer casing disposed outside the inner casing so as to define second and third expansion chambers between the inner and outer casings, a first baffle pipe disposed so as to mutually communicate the first and second expansion chambers, a second baffle pipe disposed so as to mutually communicate the second and third expansion chambers, and a tail pipe member disposed so as to communicate the third expansion chamber and the outside of the outer casing. The inner and outer casings are formed by two plate members, respectively, which are secured together when the muffler assembly is assembled. A sound absorption chamber is formed around the outer periphery of the tail pipe.

Abstract: An adjustable sound attenuating device comprised of an elongated outer main shell of a predetermined diameter, with an inlet coupling and an outlet coupling. The device has located within the shell singular or multiple independent baffle components comprised of a solid baffle plate, a perforated baffle plate, an optional perforated baffle plug, and several chambers provided by the baffle components. The solid and perforated baffle plates have a funnel shape to provide for smooth directional flow of exhaust gases. The perforated baffle plate is pierced with a plurality of openings to allow for the flow of the exhaust gases through the chambers. The perforated baffle tube is pierced with inwardly angled louvers spaced equally around the circumference and staggered to follow a spiral path lengthwise around the perimeter of the tube for routing gases through the chambers.

Abstract: A reinforced stamped muffler is provided. The muffler includes a pair of internal plates secured in face-to-face relationship and formed to define an array of tubes and chambers therebetween. The chambers are provided with at least one array of reinforcing grooves. Larger chambers defined by the internal plates may include a first array of parallel reinforcing grooves and a second array of parallel reinforcing grooves extending transverse to and intersecting the end-most grooves in the first array. All of the grooves preferably extend into intersection with planar portions of the internal plates. The muffler further includes external shells formed to define larger chambers. The larger chambers of the external shells are formed with a major pattern of reinforcing undulations and a minor pattern of undulations or grooves superimposed thereon. The minor pattern preferably includes a parallel array of grooves with end most grooves in the parallel array being intersected by orthogonally extending grooves.

Abstract: A noise reducer for an engine induction system comprises an outer duct having an inlet and outlet, and an inner duct having an inlet and outlet. The inner duct has a contained portion including the inner duct outlet and a portion of the inner duct adjacent to the inner duct outlet. The contained portion is contained in the outer duct with the inner duct outlet being adjacent the outer duct outlet. The noise reducer further comprises a closure extending away from the inner duct into engagement with the outer duct. The closure is spaced apart from the inner duct outlet along the axis of the inner duct. A resonance chamber is defined by the space between the contained portion, closure and outer duct. A chamber port is defined by the space between the inner duct outlet and the outer duct.

Abstract: A muffler is provided with a pair of plates formed to define an array of tubes therebetween. At least one external shell is secured to at least one of the plates to surround selected portions of the tubes. The shell is formed to define a plurality of chambers separated from one another by a baffle crease. The baffle crease is parallel to and abutting a selected tube of the muffler to simplify the draw of metal material in the vicinity of the baffle crease and to thereby save metal. The baffle crease is of substantially uniform depth along a major portion of its length and is free of pockets that could conceivably retain corrosive fluids.

Abstract: A compressor bleed air passageway includes a duct having an upstream section (48) which terminates in a baffle (44) and a downstream duct section (54) having a forward portion (56) which surrounds the baffle (44). Bleed air flow through openings (58) in the baffle wall (52). This reduces velocity of the bleed air stream at the duct discharge port to a value equal to or less than Mach 1.0. The baffle (44) has virtually no effect on a low-velocity, low-pressure air stream. The downstream duct section (54) may be perforated and surrounded by outer wall (64) to form sound-absorbing chambers (66).

Abstract: A stamp formed muffler includes upper and lower internal plates and upper and lower external shells secured to the respective internal plates. The internal plates are formed to include arrays of channels that are placed in register with one another to define an array of tubes. The external shells are formed to define chambers that surround selected tubes formed by the internal plates. The upper internal plate includes at least one pair of aligned channels disposed in spaced apart end-to-end relationship and in register with a continuous channel in the lower internal plate. The chambers of the external shells are separated from one another by baffle creases. The baffle crease of the upper external shell is disposed in registration with the spaced apart aligned channels of the upper external shell. As a result, the baffle crease of the upper external shell is substantially free of pockets that conceivably could trap foreign materials.

Abstract: A stamp formed exhaust muffler for mounting on a vehicle is provided. The muffler comprises a plurality of plates secured in juxtaposed relationship and stamp formed to define an array of tubes therebetween. At least one external shell is secured to the internal plates to define at least one chamber which communicates with the array of tubes. The external shell includes at least one conformal area which permits the muffler to conform to the shape of a structure on the vehicle. The conformal area may be an area of generally arcuate concavity when viewed from the exterior of the muffler or may define an internal corner on the muffler. Thus, a plane or line connecting two locations on the conformal area of the external shell will pass through the interference zone of a structure on the vehicle. The conformal area may be disposed where peripheral edges of the formed components are joined.

Abstract: A resonator used in an exhaust system of an automotive internal combustion engine. The resonator defines therein a resonance chamber and provided with an exhaust gas inlet tube through which exhaust gas is introduced into the resonator. An exhaust gas outlet tube is provided so that exhaust gas is discharged out of the resonator through the outlet tube. The inside ends of the inlet and outlet tubes are connected with a tuning tube respectively at positions which are opposite to each other with respect to the axis of the tuning tube. The opposite ends of the tuning tube are opened to the resonance chamber. The inner diameter of the tuning tube is larger than that of the inlet tube and that of the outlet tube, thereby greatly improving noise attenuating effects under resonance as compared with conventional resonators.

Abstract: A stamp formed muffler is provided with a nonplanar array of tubes. The tubes are defined by at least one pair of nested formed members. The nested members include at least one external shell having a nonplanar portion and at least one internal plate having a nonplanar portion, with the respective nonplanar portions being configured to be placed in generally nested face-to-face relationship. The nonplanar configuration comprises an array of channels, such that an array of tubes is defined by the channels when the components are placed in nested relationship to one another. One or more chambers of the muffler are defined adjacent the nested formed members. The chambers may be defined by a single plate placed in register with the nested components or by a second pair of nested members. The nested pairs of formed members is effective in dampening shell noise attributable to vibration of the formed members.

Abstract: A stamp formed exhaust muffler for mounting on a vehicle is provided. The muffler comprises a plurality of plates secured in juxtaposed relationship and stamp formed to define an array of tubes therebetween. At least one external shell is secured to the internal plates to define at least one chamber which communicates with the array of tubes. The external shell includes a conformal area which permits the muffler to conform to the shape of a structure on the vehicle. The conformal area may be an area of generally arcuate concavity when viewed from the exterior of the muffler or may define an internal corner on the muffler. Thus, a plane or line connecting two locations on the conformal area of the external shell will pass through the interference zone of a structure on the vehicle.

Abstract: A silencing device for an internal combustion engine includes an expansion chamber which may be implemented with a prechamber, a muffler or the like installed in an exhaust system of the engine. An exhaust pipe connected to the expansion chamber is provided with a double-layer structure consisting of an inner conduit through which exhaust gases flow and an outer conduit which surrounds the inner conduit. An air gap defined between the inner and outer conduits is opened into the expansion chamber at one end and closed at the other end so as to serve as a resonance chamber.

Abstract: An exhaust manifold for attachment to an engine having a plurality of exhaust ports is provided. The exhaust manifold includes an exhaust conduit that is in fluid communication with selected exhaust ports, with the exhaust conduit being formed to include separate primary and auxiliary outlet openings. The exhaust manifold also includes a tuning tube that is formed to include an inlet opening that is in acoustic communication with the auxiliary outlet opening, and an outlet opening. The exhaust manifold also has a chamber for providing a static volume that is in acoustic communication with the outlet opening of the tuning tube.

Abstract: The muffler comprises a main sound arresting chamber formed in the interior of an outer cylinder of the muffler and a bracket fixedly secured to the outer surface of the outer cylinder for mounting the muffler on a body of a motorcycle. The muffler is provided with an auxiliary sound arresting chamber formed in the interior of the bracket and communicating with the main sound arresting chamber through a connecting passage so as to increase the total volume of the sound arresting chamber, thereby permitting the output of the engine of the motorcycle to be enhanced while the sound arresting effect on the exhaust gas is improved. The main sound arresting chamber may be divided into an upstream side main sound arresting chamber portion and downstream side main sound arresting chamber portions by partition means and the auxiliary sound arresting chamber portion communicates with the upstream main sound arresting chamber portion. The connecting passage may be in the form of a plurality of small diameter holes.

Abstract: An axially asymmetric exhaust gas muffler has a perforated central exhaust duct that is circumscribed by a duality of reactive sound attenuating chambers in each of which is positioned a resonant sound attenuator.

Abstract: A silencing system for exhaust gases from internal combustion engines, comprising an intermediate silencing device for connection to the exhaust manifold of an internal combustion engine, and a final silencing device series connected to the intermediate silencing device, in which the final silencing device comprises, within an envelope, a number of spaced annular members, intersected by radial partition walls, forming series of chambers of different size, which occupy the peripheral portion of the envelope and open towards the axial portion of this latter, leaving this axial portion substantially free for passage of the flow of exhaust gases, and an idle fan is provided for acting onto the passage for the exhaust gases and onto a passage for additional air, which passages join downstream the fan into an exhaust nosepiece. Some annular members are made of a catalytically active material in order to exert a purifying action on the exhaust gases.

Abstract: Two embodiments of outboard motors incorporating improved silencing systems for the exhaust gases of the powering engine. In each embodiment, a Helmholtz resonator is provided by a resonance chamber formed at least in part by a spacer plate that is interposed between the power head and drive shaft housing of the engine and which communicates with an expansion chamber of the engine through a tuning neck. In each embodiment, the effective volume of the resonance chamber of the Helmholtz resonator is varied in response to engine speed by delivering coolant to it from the engine cooling jacket and discharging the coolant at a restricted rate.

Abstract: An integral formed fluted tube intended, for example, for use as a sound suppression device in mufflers, exhaust ejectors, etc. is disclosed. The tube is formed of a cylindrical portion with generally circular inlets and outlets and a constricted portion between those ends and within the constriction, a plurality of bypasses therethrough. The constriction may also include a frontal portion having a generally concave surface which rises to an apex and thereafter forms a plurality of convex rear portions toward the outlet end. Other embodiments are shown in the Figures. The device may be used integrally within a muffler to obtain a venturi effect for an exhaust ejector and sound suppressor.

Abstract: The silencer device set forth herein in its various embodiments consists of at least one channelling bounded by at least one turn of a flat spiral, or of a cylindrical helix, or of a tapered helix, which may be blanked-off or open at one of its ends or at both of its ends, and/or incorporate radial holes or frontal holes in one or both faces. The outermost turn of the spiral, or the outermost surface of the helix, may either provide the shell of the device, or form a part thereof.

Abstract: A flexible means is interposed between a first exhaust conduit fixed to the power unit of an automobile and a second conduit elastically supported by the automobile body, and conveys the exhaust gases of the power unit from the first exhaust conduit to the second exhaust conduit. The flexible means has a first end portion fixed to the first exhaust conduit and a second end portion fixed to the second exhaust conduit. The flexible means further has a middle portion which is a bellows which extends between and is bounded by the first and second end portions to form an expansion chamber therebetween. The chamber is fluidly connected with the first exhaust conduit and the second exhaust conduit.

Abstract: A muffler comprises two Helmholtz resonators, one tuned for high frequency and the other for low frequency. There is a resonance of the high frequency resonator volume's compliance and the effective tail pipe gas inertance which produces an undesirable low frequency noise. This is matched by the resonant frequency of the low frequency resonator, and suppressed thereby. A secondary effect to suppress noise at frequencies above said low frequency resonance due to the tailpipe gas inertance increasing linearly with frequency.

Abstract: A relatively small, lightweight muffler is provided, especially adapted to low horsepower aircraft and comprises an elongated, essentially cylindrical structure made up of inner and outer casings having sound-absorbent-material-containing chambers and pressure-wave trap elements to minimize exhaust noises. The rear end of the muffler is in the form of a cone having its apex to the rear and containing a quantity of sound-absorbent material in a rearward part thereof and the conical wall ahead of this material being perforated. One form of the structure has a convex or hemispherical front end for aerodynamic purposes in those cases where the muffler is installed externally of the aircraft. The pressure-wave traps comprise walled structures having louvered slots therein appropriately aimed to direct the pressure waves to the sound-absorbent material.

Abstract: The muffler comprises a resonator (6) which communicates by way of an outlet orifice (14) with a chamber (5). A flexible valve member (16) regulates the section of the passage through this orifice in accordance with the rate of flow of the gas through the outlet of the resonator under the action, for example, of the pressure prevailing in the resonator. When the running speed of the engine decreases, the valve member reduces the section of the passage through the orifice (16) and modifies the acoustic attenuation in the resonator. The valve member may be controlled by other parameters of the flow of the exhaust gas inside the muffler.

Abstract: The expansion chamber shell into which the gas from a noise source, such as an internal combustion engine, is rushed is held in an outer shell in a manner to define therebetween a clearance which acts as a sound damping means against the gas passing through the muffler. Thus, the noise caused by the inevitable vibration of the expansion chamber shell is prevented from being directly transmitted to the outside of the muffler.

Abstract: An inner shell having aligned first and second expansion chambers is spacedly disposed in an outer shell in a manner to define therebetween four isolated chambers upstreamly positioned two of which surround the first expansion chamber and downstreamly positioned two of which surround the second expansion chamber. The first expansion chamber is connected through respective flanged openings to the upstreamly positioned isolated chambers to allow these chambers to show a sound damping effect. The upstream and downstream portions of the second expansion chamber are connected through respective groups of perforations to the downstreamly positioned isolated chambers to allow these chambers to show a sound damping effect.

Abstract: An acoustical silencer for a gas passage or exhaust duct for a gas turbine engine, which is composed of three parts. The first comprises an absorptive surface to absorb incident low frequency sound the second comprises an acoustically lined duct attenuating high frequency sound transmitted therethrough. The entrance to the first part and the entrance to the second part are essentially coplanar. The third part is a horn-shaped plenum or conical diffuser to contain the flow and distribute the sound over the entry surface of the first part and the entrance to the second part. The entrances to both the first and second parts, being coplanar, present acoustically parallel paths to sound impinging on their common plane. The input impedances of the absorptive surface of the first part and the entrance to the second part are adjusted such that a disproportionately larger share of the incident low frequency acoustical energy passes into the first part and is dissipated.

Abstract: A straight-through flow muffler (10) is shown. A cylindrical housing (11) has an inlet (13a), an outlet (14a), and a pair of axially aligned, longitudinally spaced tubes (15, 16) extending from the inlet and outlet into the center of the muffler housing. Imperforate baffles (17, 18) separate the muffler housing into a plurality of attentuation chambers (20, 21, 22) surrounding the tubes (15, 16). A pair of sonic chokes (25, 26) are mounted in series in the tubes. The baffles and a pattern of perforations in the tubes cooperate to block flow between chambers except through the sonic chokes (25, 26) while permitting fluid communication between the tubes and the individual chambers.

Abstract: An exhaust silencer especially for turbo-charged diesel locomotives with a single exhaust outlet combines a straight through exhaust duct preferably diverging to recover velocity pressure and minimize back pressure with dual silencing means including a large expansion tank around the duct tuned to attenuate a fundamental low frequency exhaust noise peak and smaller reactive chambered means in the duct sized to attenuate a selected mid range of higher frequency exhaust noise. Various features are included.

Abstract: A muffler comprising a housing (12) having end caps (16, 18) and partitions (32, 38, 42) which divide it into first and second expansion chambers (40, 44), a flow chamber (36), and a resonator chamber (34). An inlet tube (20) passes through end cap (16) and partitions (38) and (32) to open into chamber (34): it has perforations (58) and (62) which afford communication with chambers (40) and (36) respectively. An outlet tube (24) passes through end cap (18) and partitions (42) and (32) to open into chamber (36): it has perforations (70) which afford communication with chamber (44), and includes anti-whistle beads (72). A conversion-divergent nozzle (80) is located in tube (22) at its end opening into chamber (36). Apertures (190) are provided to afford limited flow of gas through chamber (34) from tube (20) to chamber (36).

Abstract: An exhaust silencer for an outboard engine including an expansion chamber for reducing the exhaust noise. A reflection chamber having an open end and a closed end is placed with its open end communicating with the expansion chamber at a location which is reversely spaced from the open end of an exhaust pipe discharging into the expansion chamber. This enables the engine to be operated optimally in a plurality of engine speed ranges and for the silencer to occupy a minimal volume.

Abstract: A muffler for use with machines such as pneumatic drills consists of an elastomeric housing divided into an admission chamber and a series of muffler chambers. Within the housing are an inlet conduit communicating with the admission chamber and each muffler chamber, an exhaust conduit communicating with each muffler chamber as well as with a tail pipe outside the housing, and a Helmholtz resonator communicating with the admission chamber.

Abstract: A muffler (10) for reducing the noise level of gases passing therethrough is disclosed. The muffler (10) includes a housing (12) including a longitudinally extending wall (14) and a pair of opposite end walls (16, 18). Baffle plates (32, 38, 42) divide the interior space of the housing (12) into a Helmholtz resonator chamber (34), a flow chamber (36), an inlet broad band attenuator chamber (40) and an outlet broad band attenuator chamber (44). An inlet tube (20) extends through an inlet port (21) in the end wall (16), through a hole (48) in the baffle plate (38) and through a hole (50) in the baffle plate (32). An outlet tube (22) passes through an outlet port (23) in the end wall (18), through a hole (52) in the baffle plate (42) and through a hole (54) in the baffle plate (32). Exhaust gases enter the muffler (10 ) through the inlet tube (20), pass through holes (62) into the flow chamber (36) and exit the muffler (10) through the outlet tube (22).

Abstract: A muffler for use in conjunction with a high intensity, low frequency noise-propagating open pipeline is disclosed. The muffler features an acoustically lined expansion chamber in tandem with a reasonator chamber. The length of the expansion chamber is approximately 25 percent of the wavelength to be attenuated. An exit tube, which passes through the resonator chamber to lead from the expansion chamber to the muffler outlet, is partially perforated with the perforations being restricted to at most the 50 percent of the exit tube closer to the muffler outlet. Audible noise which is emitted by the open pipeline is reduced by up to 30 dB and 11 .DELTA. dB(A) and brought to within acceptable levels.

Abstract: A sound absorber for intermittent exhaust gas, particularly for use in connection with a compressed air operated motor employed, for example, in a hand grinder. The sound absorber is arranged predominantly in the housing of the motor and includes an exhaust air discharging channel having an alternately varying cross-section to define a succession of continuously alternating narrow and wide passages for changing continuously the direction of flow of the exhaust air about an angle that is always lower than 90.degree. with respect to the axis of the discharge channel so that the ratio of successive minimum and maximum cross-sections of the channel is at most 4:1. The discharge channel is terminated with a nozzle plate defining a plurality of outlet nozzles the central axes of which converge in the direction of flow.

Abstract: An exhaust silencer for a railway locomotive with a supercharged, six-cylinder diesel engine developing a power of about 200-250 HP has a cylindrical body closed at each end by an end wall and subdivided into three resonance chambers and three gas expansion chambers by five dished baffle-plates, the fourth and fifth baffle-plates each having four tube sections. To optimize the acoustic performance specific dimensions of the chambers, of the tube sections, of a perforated induction pipe and of an outlet pipe are prescribed.

Abstract: A muffler for reducing the audible noise level of exhaust gases emitted by combustion engines has an inlet tube with a patch of louvers or perforations and is arranged so that all or substantially all the gas flowing through the muffler is forced through the patch into an expansion chamber from which it flows by either cross bleeding through a patch of louvers or perforations into an outlet tube or to a chamber opening into the inlet end of the outlet tube. A "splitter" partition may be used to control flow through the louvers and provide additional attenuation. An imperforate portion of the inlet tube is used as a driven tuning tube with a resonator chamber to form a Helmholtz low frequency attenuation system, the performance of which may be improved in some cases by use of an orifice in a wall of the resonator. Also disclosed is a muffler in which all the gas flows through a louver patch in the outlet tube and an imperforate part of the outlet tube is used as a part of an aspirating type Helmholtz system.