US2274459A

US2274459A - Muffler

Info

Publication number: US2274459A
Application number: US168944A
Authority: US
Inventors: Carl F Rauen
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-10-14
Filing date: 1937-10-14
Publication date: 1942-02-24
Anticipated expiration: 1959-02-24

Description

Feb. 24, 1942. Q E R N 2,274,459

MUFFLER Filed Oct. 14, 1957 2 Sheets-Sheet 1 INVENTOR. v Carl E Fauen EQW'MK AT RNEYS.

C. F. RAUEN MUFFLER Feb. 24, 1942.

Filed Oct. 14, 1937 2 Sheets-Sheet 2 Patented Feb. 24,. 1942 UNITED STATES PATENT OFFICE (Granted underthe act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 68 Claims.

Theinvention described hereinmay be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to mufflers for silencin the exhaust of internal combustion engines, the intake of air compressors and the like.

Heretofore, exhaust noises have been silenced primarily by restricting the flow of th gases by means of several bailles. These baflles are usually either in series so that the gas passes directly from one to the other, or so arranged that the gases reverse their flow after passing through With my designs I can muflie the exhaust gases from internal combustion engines, with little or no back pressure, and with mufflers relatively smaller than those now in use.

A primary object, therefore, of this invention is to separate the sound energy from the exhaust gas stream, with little or no restriction on the flow of the gas stream; that is, to separate the sound from the gas stream by directing it to one place until its energy is destroyed, while the gas stream is allowed to escape at another place.

To obtain this control of the sound and gas, I make use of what I term sound trap chambers or dead chambers, which will be hereinafter more fully explained, and the reflecting and focusing properties of the conic sections, and other shapes, to reflect, focus, concentrate and destroy sound; I also make use of the sound absorbing and destroying properties of such materials as steel wool, mineral wool, asbestos," etc., which are so arranged in themuiiler that the sound is absorbed or destroyed by entering the interstices of the material, where it travels devious and tortuous paths, while the exhaust gas stream is led through the muffler with little or none of it passing through this absorbing material. A further property of the above material is its comparative softness; that is, it does not reflect sound like hard material. a}

It is a well known fact that sound can be reflected and focused substantially in the same manner as light, by means of reflectors, and hence I make use of the reflecting and focusing properties of reflectors shaped to the conic sections; that is, the parabolic, hyperbolic, elliptical, or spherical reflectors, or any combination of the above, to control the sound energy and produce silencing by reflecting, focusing, or concentrating the sound at one place by means of the foregoing methods, either separately or in any combination, until its energy is destroyed, whil the gas stream is allowed to escape from another place.

Use is also made of thereflecting properties of flat plates and inclined surfaces or, for that matter, any shape of inclosure wherein the sound can be trapped and caused to lose its energy by rapid reflection between the walls of said enclosure, into which it has been introduced, while the gas stream is led to atmosphere by a separate path, minus thegreater part of the sound energy.

Since sound can be focused or concentrated by various types of reflectors, I have designed and built mufflers wherein the exhaust sound is concentrated or trapped by one or more reflectors, or sound traps, while the gas is permitted to escape at a place where the least amount of sound can escape with it.

Due to the high efficiency of the methods of silencing used in my invention, very little restriction need be put on the flow of the gas stream, in order to confine the sound to the muffler until it is destroyed, and in consequence of this high silencing efficiency, a much smaller and cheaper muflier can be made to do the work of the larger ones now in use.

It is understood that any hard surface will reflect sound, regardless of its shape, in a manner complying with the well. known laws of reflection, and that soft surfaces absorb sound. It is further understood-that every time sound is reflected, it loses some of its energy. The mufiier designs shown in this application preferably are made of sheet metal stampings which are fastened together asby welding. They can, however, be made of castings. I

It is' another object of this invention to provide baffies to break up the sound waves and produce silencing without the gas stream flowing through them, and with little effect on the flow of the gas stream, as well as to cause these bafiles to act more than once on the sound, that is, to cause their ability to destroy sound to be brought into play at least twice.

A further object of this invention is to provide a muffler with relatively small chambers, so that the sound energy will be'destroyed in a very short time within said chambers.

A still furtherobject of this invention is to prevent the recombining of the sound wave fronts after being broken up by baflles.

A still further object is to provide a muffler that is highly eflicient, simpl in construction and cheap to manufacture.

of a mufller and'so arranged that little or none of the exhaust gas passes through said chamber on its way to atmosphere, said communication forming an acoustic coupling between said gas passageway and said chamber and opening abruptly into said sound trap chamber, the areaof said communication being substantially less than the cross sectional area of said chamber, whereby the sound, after passing through said communication into said chamber, expands, as is its natural tendency, and is destroyed by refiection or otherwise, and little or none of said sound returns to said passageway, due to the restriction offered by said communication.

This application is a continuation in part of my prior application Serial No. 427,312, filed February 10, 1930, for Muffler, now Patent No. 2,138,510 issued November 29, 1938.

With the foregoing and other objects in view, as will hereinafter appear, my invention consists of certain novel features-of construction, combinations and arrangements of parts, as will be hereinafter described in detail and particularly set forth in the appended claims.

For a better understanding of the invention, reference may be had to the accompanying drawings, of which there are two sheets and wherein:

Fig. 1 is a longitudinal sectional view of one embodiment of my invention;

Fig. 2 is a cross-sectional view taken in a plane on the line 2-2 of Fig. 1, looking in the direction of the arrow;

Fig. 3 is a longitudinal sectional view of a modified form of muffler embodying my invention;

Fig. 4 is a cross-sectional view taken in a plane on the line 44 of Fig. 3;

Fig. 5 is a longitudinal sectional view of a modified form of muffler embodying my invention;

Fig. 6 is a cross-sectional view taken in a plane on the line 66 of Fig. 5, looking in the direction of the arrow;

Fig. '7 is a longitudinal cross-sectional view of another modified form of muffler embodying my invention;

Figs. 8, 9, 10, 11 and 12 are fragmentary views illustrating modified forms of sound trap chambers which may be employed in lieu of the sound trap chamber illustrated in the modification disclosed in Fig. 7, or in lieu of the sound trap chambers illustrated in any other modifications of the invention herein illustrated.

Fig. 13 is a longitudinal sectional view illustrating a modified form of sound tra construction;

Fig. 14 is a longitudinal sectional view illustrating an additional embodiment of my invention;

Fig. 15 is a longitudinal sectional view illustrating another modified form of the invention;

Fig. 16 is a longitudinal sectional view illustrating a further modified form of the invention, and

Fig. 17- is a longitudinal sectional view illustrating a modification of Fig. 1.

Referring to Figs. 1 and 2, the muffler consists of a tube 20 which may be of an desired crosssectional shape extending the full length of the muffler and adapted at one end thereof to be.

may be used for silencing the air intake to an engine as well as the exhaust thereof. The tube 20 is illustrated as being provided with groups of relatively small openings or perforations 22. Surrounding these groups of holes and having communication with them, are the sound traps, sound trap chambers, dead chambers, sound attenuating chambers, or acoustic chambers 24, illustrated as being formed by the opposed annular parabolas and 26, which are fastened together by welding or otherwise, so as to form a substantially air-tight joint. The inner diameters of the parabolas are pressed on or otherwise secured to the tube 20 and so disposed with respect to the holes or apertures 22 that one sound trap is afforded communication through a group of holes 22 with the interior of the tube 20. The number of sound traps 24 required depends on the results desired and the characteristics of the noise to be silenced.

The gas stream from the engine enters the muffler unit at the end 28 thereof and flows down the tube while the sound energy entrained in the gas stream passes into the sound traps 24 where, after expansion, the sound energy is dissipated or destroyed by reflection, focusing, or in any other manner, within the sound traps, so that the gas stream emerges from the outlet end 30 with little or no attendant noise.

It can readily be seen that in this design of mufiier there are no baffles to offer restriction to the flow of the gas stream and that the gas has a direct passage through the center of the muilier.

In the modification illustrated in Figs. 3 and 4, the sound traps 34 are formed by a different kind of annular parabola 35, the two sections being made in halves and welded together and subsequently welded to the tube 4|], as illustrated, each sound trap having a restricted communication with the tube through a series or group of perforations or holes 32.

I have found by experiment that the sound traps 24 and 34 can be of various shapes without affecting the silencing characteristics thereof. The sound energy, after entering the sound traps. destroys itself within the sound traps, and very little, if any, of said sound energy which passes into the sound traps escapes therefrom, due to the fact that the sound energy, after passing into the sound traps, expands, and the communication between the sound trap and the tube through which the exhaust gas stream flows is relatively restricted.

In muiliingunits embodying the arrangement illustrated in Figs. 1 and 2, several sound traps are needed in order to produce a desirable degree of sound attenuation, but offsetting this need of a plurality of sound traps is the fact that this type of muffler has comparatively no back pressure as the gas stream passes straight through the mufiling unit.

The groups or series of

holes

22 and 32 break up the sound energy somewhat as it enters the sound traps, after which still more energy is taken from the sound by reflections within the sound traps. However, some of this sound energy, which has been greatly reduced by the aforesaid reflections, may be reflected in this weakened condition, back through the holes or apertures, in which case it would be further weakened and would mingle with the sound energy in the pipe and be acted on again by the following sound traps. It will be seen that the holes or openings act twice on breaking up the sound energy without offering resistance to the flow of the gases. The holes are preferably few in numberaand comparatively small, to prevent most of the sound energy which passes into the sound traps from being reflected back through the a openings. It will'be understood that there is more tendency for the sound to pass into the for the sound energy to escape from the sound trap through the openings, as the energy of the sound is greatly reduced by this time.

In Figs. and 6 there is illustrated a modification of the sound traps 24 and 34 formed by the sound traps through the openings than there is I annular parts 45 surroundingthe perforated tube 50 and which sound traps may be filled with steel wool or other sound absorbing material to absorb the sound-energy from the gas as it passes down the tube 50; that is, the sound energy passing through the openings 42 passes into the interstices of the'steel wool or other material, where the energy of the sound is absorbed or destroyed.

In the mufllers illustrated in Figs. 1 to 6, the idea is to cause the destruction of sound energy by providing closed chambers or sound traps through which there issubstantially no gas flow, but into which the sound energy can pass and be trapped until it is dissipated while the gas stream passes to atmosphere substantially free of all or the major portion of the sound energy.

In the modification illustrated in Fig. 7, the muffler consists of a tube 60 having a baflle 62 secured inside the tube intermediate the ends thereof. The tube 60 adjacent the bafile 62 and on each side thereof is provided with a plurality of apertures 64 and 66. The tube 60 is arranged within a shell 68, and the space between the inside of the shell and the outside of the tube is closed at one end thereof by an end plate 10 and at the other end thereof by a sound trap indicated generally at 12 to provide an annular chamber I4. A small group of openings 16 may be provided adjacent the inlet end I8 of the tube for affording communication between the interior of the tube and the chamber I4. The sound trap 12' arranged at the outlet end 80 of the tube may consist of a pair of like annular members 82 secured together and provided with an intermediate partition 84, the members 82 and the partition 84 being secured at the internal diameter thereof to the exterior of the tube 60, and a relatively restricted communication in the form of a series of relatively small openings 86 may be provided in the walls of the tube 60 for affording communication between the interior thereof and the sound trap 12 on each side of the partition 84 thereof. In operation, the exhaust gas stream from the engine enters the tube 60 in the end 18 thereof,

flows out of the tube through the openings proappreciable gain in terms of top speed of the vehicle or practical benefits to the engine.

In Fig. 8 there is illustrated a modification of the annular sound trap 12, which differs therefrom in that a pair of baffle plates 90 are arranged within the sound trap chamber 92 in lieu of the single partition 84 and, so as to provide a space therebetween. Communication between the tube or the interior of the tube 04 and the sound trap chamber 92 is obtained by an opening formed by a plurality of relatively small apertures 96 communicating with the space between the baille plates 90, and communication between the space between the bafile plates 90 and the space within the sound trap upon each' side thereof is provided by means of, an annular series of relatively small openings 98.

In Fig. 9 another modification. of the sound trap chamber is illustrated, in that the annular sound trap chamber I02 is provided with a single annular partition I04 and an intermediate tube I06 surrounding the tube I08. Communication is afforded between the interior of the tube I08 through which the exhaust gas stream flows and i the interior of the tube I06 by an opening H0 formed by a series of relatively small apertures, and communication is provided between the interior of the tube I06 and the sound trap chamber I02 upon each side of the partition I04 by a series of relatively small holes H2. 7

In Fig. 10 there is illustrated another modified form of sound trap chamber wherein an intermediate tube H4 is arranged externally of the tube II5 through which the exhaust gas stream flows and within the annular sound trap cham ber IIIE; The sound trap chamber 1 I6 is shown as being divided by a pair of partitions I I 8. Communication is afforded between the interiors of the two tubes II4 and H5 by two series of relatively small openings I20. Communication between the interior of the tube I I4 and the space between the baffles II8 may be provided by a series of holes I22, and each of the baflles II8 may be provided with an annular series of holes I24 for affording communication with those portions of the sound trap chamber I I6 disposed outwardly thereof.

In Fig. 11 there is illustrated a modified form of sound trap chamber wherein an annular partition I26 divides the space within the annular sound trap chamber I28, and the partition is provided with an annular series of holes I30 for affording communication between the portions of the sound trap chamber I28 disposed on opposite sides thereof. Communication between one portion of the sound trap chamber I28 and the interior of a tube I32 through which the exhaust gas stream flows may be provided by an opening formed by a series of relatively small holes I34.

In Fig. 12 there is illustrated another modification of a sound trap chamber wherein a battle or partition I38 made of a non-inflammable fabric, such as woven asbestos, is provided for dividing the space within a sound trap chamber I38, and communication is afforded between the sound trapchamber I38 upon each side'of the partition I36 by openings formed by a series of relatively small holes I40.

In Fig. 13 there is illustrated another form of silencing or sound trap chamber that is cylindrical in construction and consists of three cylindrical chambers I42, I44 and I46 arranged radially outwardly of a tube I48 throughwhich the exhaust gas stream flows and formed by a plurality of concentrically arranged tubes or pipes having their ends closed by plates I50 and I52 which thereby secure the series of tubes to the tube I48 through which the exhaust gas stream flows. Communication between the tube I48 and the chamber disposed. externally thereof is provided 'by a series of relatively small holes I54, and the outer walls of the chambers I46 and I44 are each provided with a series of relatively small holes I56 whereby communication between the chambers I42, I44 and I46 is provided.

In Fig. 14 there is illustrated a modified form of muffler construction consisting of a plurality of chambers of different volume, all communicating with each other in series and thereby providing a silencing means of considerable capacity for attenuating the sound; energy entrained in the exhaust gas stream. The tube I60 provides a conduit through which the exhaust gas stream flows and which may be arranged within a tube I62, which tube I62 may be arranged within a tube I64. A pair of headers I66 may be connected to the ends of the tube I62 to close a space between the tubes I64 and I60. The space between the tubes I62 and I64 may be divided by a plurality of annular plates I68, I and I12, and the space between the tube I62 and I60 may be divided by a plurality of annular plates I14 and I16 so as to provide a series of chambers of different volume. Communication may be provided between the interior of the tube I60 and a chamber I18 by an opening formed by a plurality of relatively small holes I80 formed in the walls of the tube I60. The annular chamber I18 communicates, by means of a series of openings I82 and I84, with the chambers I86 and I88 disposed outwardly of the chamber I18, and communication between the chamber I86, the chamber I90, the chamber I92, the chamber I94 and the chamber I96 may be established by openings I98 formed by a series of holes for providing communication between adjacent chambers so that all of the chambers are connected in series.

In Fig. there is illustrated another modiflcation of the invention, wherein a body including a shell 200 closed at its ends by

plates

202 and 204 is provided with an opening 206 in the plate 202 for receiving the exhaust gas. A reflector or baifie 251 is arranged within the shell and provided with a series of relatively small openings 258. A tube 266 is arranged within the shell and has one end projecting through the end plate 204. The end of the tube 266 within the shell is closed by a plate 268, and a plate 21I is arranged within the shell 200 and spaced from the end thereof to define a sound trap chamber 210 and for supporting the inner end of the tube 266. The tube 266 is provided with a series of perforations 261 through which the exhaust gas stream flows and is also provided with an opening 269 comprising a series of relatively small holes for affording communication between the interior of the tube 266 through which the exhaust gas stream flows and the sound trap chamber 210, the gas escaping from the tube 266 at the end 216 thereof.

In operation, the muffler illustrated in Fig. 15

I would operate as follows: The gas, after passing through the holes 258 in the reflector 251, enters the perforated tube 266 through the holes 261 and passes out the outlet 266, while any sound that escapes from the reflector 251 and enters the tube 266 would, due to its tendency to expand, pass through the holes 269 into the sound trap 210. The sound, after entering the sound trap. expands and is reflected within the sound trap until its energy is destroyed.

It is understood that some of the sound energy will have a tendency to reenter the tube 266 from the sound trap 210, and such sound as would pass through the holes 269 would be broken up thereby, after which such sound energy would tend to neutralize oncoming sound in the tube 266 by interference therewith and thereby lose its energy. One or more of the sound traps 210 can be used.

In the modification illustrated in Fig. 16, two opposed reflectors 295 and 296 are provided on the front end. These reflectors can be parabolical or elliptical. The reflector 295 is provided with an inlet port 291, and the reflector 296 supports a perforated tube 299 which has an opening 300 into the reflector chamber 30I and an opening 302 into the sound trap chamber 303 and which is supported on its rear end by the plate 304. perforated tube 305, the other end being supported by the reflectors 296 at 306. A sound trap 301 is thus formed between the tube 305, the plate 304, the reflector 296 and the body 308. The tube 306 is provided with perforations 309 and with an outlet 3| 0 for the exhaust gases. This outlet has no communication with the sound trap 301. The gas and sound, after passing through the inlet 291 expand in the reflector chamber 30I where part of the sound energy is destroyed by the opposed reflectors. The re maining sound in the gas then enters the tube 299. Practically all of this sound passes down to the sound trap 303, where it is trapped and destroyed while the gas passes out the holes 3II in the tube 299 into the chamber 3I2 formed between the tube 299 and the tube 305 and their sustaining ends 296 and 304.

Any sound passing out the holes 3II into the chamber 3I2, or at least most of it, passes through the holes 309 in the tube 305 and into the sound trap 301, where it expands and is trapped and destroyed by reflection back and forth within the sound trap. Some of the sound energy is destroyed by the fact that the wave fronts are broken up by passing through the small holes 309 into the sound trap, and any sound that tends to pass from the sound trap back to the chamber 3I2 has its wave fronts also broken up in passing back through the holes 309. Thus the holes 309 act twice in destroying the sound waves, without any hindrance to the gas flow. The gas then passes from the chamber 3| 2 to atmosphere through the outlet 3I0. By providing the sound trap 301, I can put more holes 3II in the tube299, thus reducing back pressure, and while this permits more sound to escape out the tube 299, it is trapped and destroyed by the action of the sound trap 301. If desired, the sound trap 301 may be fllled with steel wool or other sound absorbing material.

In Fig. 17 is illustrated another modification wherein sound trap or acoustic chambers, similar to those illustrated in Fig. 1 are disposed in advance of a sound trap chamber opening into the gas passageway, but thru which chamber the gas does not flow on its way to atmosphere.

As illustrated, 3I4 is a tube adapted to be attached to the exhaust pipe of an internal combustion engine and is provided with openings 3"; thru which the gas flows into the chamber 3! from whence it flows to atmosphere thru the outlet 320.

The body 322 has a header 324 disposed at one end thereof, and another header 326 disposed at the other end thereof.

Spaced along the tube 3I4 is a plurality of transverse partitions 328 which with the body form sound trap or acoustic chambers 330. Openings 332 spaced along the tube 3I4 provide a restricted communication from said tube to said chambers 330.

A header 334 is disposed at one endof mufller The plate 304 also supports one end of the energy in said gas is absorbed or attenuated by the

acoustic chambers

330 and 336.

It will be observed, in all the modifications illustrated, that the sound trap chambers are arranged radially outwardly of the tube through which the exhaust gas stream flows and that the communication between the tube through which the gas stream flows and the sound trap passed into the sound trap chamber and expands therein, the major portion of the sound energy will be trapped or confined within the'souhd trap chamber where it will be destroyed or dissipated. It is to be understood that the sound traps or sound trap chambers illustrated in the various embodiments may be interchanged and that in connection with a mufller of the straight through type, it is desirable to use a plurality of sound trap chambers disposed about the tube through which the exhaust gas stream flows, in order to obtain desirable sound attenuation.

The muffler constructions illustrated may be is restricted so that after the sound energy has formed of stampings welded together or in any other suitable manner.

The claims herein are directed to embodiments. of my invention having a sound trap chamber beside a passage for sound entrained gases and acoustically connected to such passage, through an opening or openings in a side wall of such passage, providing restricted communication from the sound trap chamber to such passage, and to certain features of these embodiments which are not specifically claimed in my Patents Nos. 2,138,510 and 2,229,672 and my co-pending application Serial No. 168,946, filed October 14, 1937. The subject matter of the claims in the instant application is claimed more broadly in my Patent No. 2,138,510, and subject matter disenergy out of a gas stream, a passageway comprising a tubular member through which the gas stream flows, an inlet to said device connected to one end of said passageway, an outlet from said device for said gas stream connected to the other end of said passageway, and means providing an enlarged dead chamber separate from and adjacent one end of said passageway and having a restricted communication therewith, said chamber having a cross sectional area greater than that of said communication and being adapted to permit the rapid expansion. of sound energy within saidchamber after passing through said communication, said restricted communication operating to trap sound energy within said chamher, said device being constructed so as to provide a plurality of relatively small openings extending at least partially around and along the length of said passageway aflording said communication between said dead chamber and said passageway.

2. A silencer for sound entrained flowing gases comprising a tube forming at least part of a passageway for the flow of gas through said silencer, a casing surrounding said tube, said tube being provided with a gas inlet opening at one end thereof, an outlet opening in the walls thereof, and a further outlet opening at the other end thereof, one of said outlet openings constituting a gas outlet, the other outlet opening com,,

prising a series of relatively small apertures and constituting a sound energy outlet having communication with means providing a sound trap chamber within said casing, said chamber being constructed and arranged so as to trap sound energy therein, an expansion chamber in communication with the gas outlet of said tube and having an outlet opening communicating with atmosphere, and means providing a further sound trap chamber within said casing substantially closed on all sides except for a restricted open area that forms an acoustic coupling with said expansion chamber, one of said sound trap chambers being arranged around said tube.

3. An acoustic sound attenuating device for silencing sound entrained flowing gases comprising a unit having a gas inlet opening and a gas outlet opening, means including a tube providing a straight-through substantially unrestricted part of a passageway for the flow of gases between said openings, means providing a sound trap chamber of annular shape and uniform sec tion from one end to the other end thereof substantially closed on all sides and disposed around said passageway, a restricted opening acoustically coupling directly the interior of said chamber and said passageway, the cross sectional, area of said chamber being appreciably greater than the cross sectional area of said last-mentioned opening, and said sound trap chamber being so disposed and arranged that little or none of said gas passes through said chamber on its way from said inlet to said outlet opening.

4. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeratipn of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision. for connecting one of said openings to a gas conducting member which communicates with the cylinders of the engine, a tubular member within said casing and forming at least part of a gas passageway between said openings, said tubular member being providedwith a gas inletopening at one end thereof, an outlet opening in the walls thereof, and a further outlet opening .at the other end thereof, one of said tubular member outlet openings constituting a gas outlet, the other of said tubular member outlet openings providing an acoustic coupling, with means providing a sound trap chamber within said casing, said coupling providing a restricted communication from said chamber to the interior of said tubular member, said chamber being constructed and arranged so as to permitthe rapid expansion of the sound energy therein and so as not to form part of the path traversed by the major portion of said gases, an expansion chamber dis? posed at the inlet end of said tubular member and in communication with the inlet opening thereof, an expansion chamber in communication with the gas outlet of said tubular member and having an outlet opening communicating with said casing outlet opening, and means providing a further sound trap chamber within said casing having a restricted communication with one of said expansion chambers, one of said sound trap chambers being arranged around said tubular member.

. 5. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings forsaid gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of the engine, a tubular member within said casing and forming at least part of a gas passageway between said openings, said tubular member being provided with a gas inlet opening at one end thereof, an outlet opening in the walls thereof, and a further outlet opening at the other end thereof, one of said tubular member outlet openings constituting a gas outlet, the

other of said tubular member outlet openings pro viding an acoustic coupling, with means providing a sound trap chamber within said casing, said coupling providing a restricted communication from said chamber to the interior of said tubular member, said chamber being constructed and arranged so as to permit the rapid expansion of the sound energy therein and so as not to form part of the path traversed by the major portion of said gases, an expansion chamber disposed at the inlet end of said tubular member and in' communication with the inlet opening thereof, an expansion chamber in communication with the gas outlet of said tubular member and having an outlet opening communicating with said casing outlet opening, and means providing a further sound trap chamber within said casing having a restricted communication with one of said expansion chambers, one of the sound trap chambers being arranged across the end of said casing.

6. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/ or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising an imperforate casing having transverse members and inlet and outlet openings for said gases, means mounted on said members and defining at least part of a gas passageway within said casing between said openings, and having an open area in the walls thereof, said silencer having provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of the engine, and means defining a sound trap chamber within said casing and around said part of said gas passageway, said sound trap chamber being acoustically coupled to said passageway by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication, the maximum effective cross-sectional area of said part of said gas passageway being less than the maximum cross-sectional area of said chamber.

7. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, and having an open area in the side walls thereof, and means comprising transversely extending members defining a sound trap chamber separate from and extending at least partially around said passageway, said sound trap chamber being acoustically coupled to the passageway by'means of said open area, said open area comprising a plurality of relatively small apertures disposed along the length of said passageway and providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication.

8. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means including a tubular member of substantially uniform cross sectional area defining a gas passageway between said openings, and having an open area in the side walls thereof, and means including transversely extending members delining a sound trap chamber separate from and at least partially around said passageway, said sound trap chamber being acoustically coupled to the passageway by means of said open area, said open area comprising a plurality of relatively small apertures disposed along the length of said passageway and providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication.

9. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches said silencer having inlet and outlet openings I partially around said passageway and providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, said sound trap'chamber being abruptly enlarged adjacent said communication. v

10. An acoustic silencer for silencing the noise arranged, separate from of sound entrained flowing gases of the intake and/ or exhaust system of an internal combustion comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conductin member which communicates with the cylin ers of the engine,

means including a tubular member of substan tially uniform cross sectional area defining a gas passageway between said openings, and having an 11. in acoustic silencer for silencingthe noise such as are used in motor vehicles, said noise energy in said chamber, said sound trap chamber being "abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein, said sound trap chamber being constructed and arranged so that little or none of said gases pass through said sound trap chamber on their way from said inlet to said outlet opening, the cross sectional area of said chamber being materially greater than the cross sectional area of said tubular member.

13. An acoustic silencer, for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system oi! an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of'pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means including two expansion chambers and a conduit for conducting gases therebetween, defining a gas passageway between said openings and within said casof sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noisecomprising a conglomeration of pitches, said silencer comprising a body having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member whichcommunicates with the cylinders of the engine, means including a tubular member of substantially uniform cross sectional area through which the gases fiow and defining a gas passageway between said openings, and means comprising transverse members defining a sound trap chamber separate from said passageway and at least partially around said tubular member, said sound trap chamber being acoustically coupled to the passageway by means of an open area in said passageway, the cross sectional area of said sound trap chamberbeing materially greater than that of said tubular member, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication.

12. An acoustic silencer for silencing the'nolse of sound entrained flowing gases of ,the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles,

said noise comprising a conglomeration of pitches,

,said silencer comprising a casing having inlet and outlet openings for said gases and provision for connectingone of the openings to a gas conducting member which communicates with; the cylinders of the engine, means including a tubu- Ia! member of substantially uniform cross sectionalarea through which the gases flow and defining a gas passageway betweensaid openings, and means including a transversely extending member defining a sound trap chamber and at least partially around said passageway, said sound trap chamber being acoustically coupled to the passageway by means of an open area in said tubular member, said open area providing a restricted communication from saidsound trap chamber to said passageway which operates to trap sound ing, one of said expansion chambers having an' open area in the walls thereof, and means defining a sound trap chamber separate from said passageway, said sound trap, chamber being acoustically coupled to the expansion chamber by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber,

said sound trap chamber being abruptly en-c larged adjacent said communication.

14. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means including two expansion chambers and a conduit for conducting gases therebetween, defining a gas passageway between said openings and within said casing, one of said expansion chambers having an open area in the walls thereof, and means defining a sound trap chamber separate from said passageway, said sound trap chamber being acoustically coupled to the expansion chamber by means of said open area, said open area providing a restricted communication from said sound trap chamber to said' passageway which operates to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication, said sound trap chamber being disposed around a part of said gas passageway.

15. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles,

sageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum effective cross sectional area of that part of said passageway in which said openarea is, provided being less than the maximum cross sectional area of said chamber.

16. An acoustic'silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between said openings, and having an open area in theside walls thereof, said open area comprising a plurality of relatively small apertures, means defining a sound trap chamber, separate from said passageway and acoustically coupled thereto by means of said apertures, said apertures providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum effective cross sectional area of that part of .said passageway in which said open area is provided being less than the maximum cross sectional area of said chamber.

17. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases, and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures disposed along the length of said passageway, means defining a sound trap chamber, separate from said passageway and acoustically coupled thereto by means of said apertures, said apertures providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases.

18. An acoustic silencer for silencing the noise of sound entrained flowing gases of th intake and/or exhaust system of an internal'combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for communicates with the cylinders of said engine,

means defining a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures disposed along the length and at-lcast partially around said passageway, means defining a sound trap chamber, separate from said passageway and acoustically coupled thereto by means of said apertures, said apertures providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said .sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases.

19. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combusfrom and arranged at least partially around said passageway, said sound trap chamber being acoustically coupled to said passageway by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum effective cross sectional area of that part of said passageway in which said open area is provided being less than the maximum cross sectional area of said chamber.

20. An acoustic silencer for silencing the noise 7 of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, and having an open area in the side walls thereof, means defining a sound trap chamber separate from and at least partially around said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway and which communication operates to trap sound energy in said chamber, at least part of the wall of said passageway forming a part of said sound trap chamber defining means, said sound trap cham-- ber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, said sound trap chamber being constructed and arranged so as not to form a part of the passageway traversed by the major portion of the gas on its way through said silencer, the maximum efiective cross sectional area of that part of said passageway in which said open area is provided being less than the maximum cross sectional area of said chamber.

21. Ar. acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said. noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between said openings,.and having an open area in the side walls thereof, said open area comprising a lurality of relatively small apertures, means defining a sound trap chamber separate from and at least partially around said passageway, said sound trap chamber being acoustically coupled to said passageway by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum effective cross sectional area of that part of said passageway in which said open area is provided being less than the maximum cross sectional area of said chamber.

22. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures disposed along the length of said passageway, means defining a sound trap chamber, separate from and at least partially around said passageway, said sound trap chamber being acoustically coupled to said passageway by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases.

23. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motorvehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conductin member which, communicates with the cylinders of said engine, means defining a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures disposed along the length and at least partially around said passageway, means defining a sound trap chamber, separate from and at least partially around said passageway, said sound trap chamber being acoustically coupled to said passageway by means of said open area, said open 'area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowin gases.

24. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member through which the gases flow forming at least part of a gas passageway within said casing between said openings, and having an open area in the side walls thereof, means defining a sound trap chamber within said casing, separate from said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum effective cross sectional area of said tubular member being less than the maximum cross sectional area of said sound trap chamber,

25. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles,-

said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas, conducting member which communicates with the cylinders of said engine, a tubular member of substantially uniform cross sectional area throughout its length through which gas flows forming at least part of a gas passageway within said casing between said openings, and having an open area in the side walls thereof,'means defining a sound trap chamber within said casing, separate from said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chambenbeing abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum efiective cross sectional area of said tubular member being less than the maximum cross sectional area of said sound trap chamber.

26. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means comprising a tubular member through which gas flows defining at least part of a gas passageway between said openings, said tubular member having an open area in the side walls thereof, means defining a sound trap chamber separate from said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway and which communication operates to trap sound energy in said chamber, at least part of said tubular member forming a part of said sound trap chamber defining means, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum effective cross sectional area of said tubular member being less than the maximum cross sectional area of said sound trap chamber.

27. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member forming at least part of a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures, means defining a sound trap chamber within said casing, separate from said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway,

'said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum eifective cross sectional area of said tubular member being less than the maximum cross sectional area of said sound trap chamber.

28.' An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine suchas are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member forming at least part of a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures disposed along the length of said tubular member, means defining asound trap chamber, separate from said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases.

29. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member forming at least part of a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures disposed along the length and at least partially around said tubular member, means defining a sound trap chamber, separate from said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and 'operating toappreciably attenuate the noise of said sound entrained flowing gases.

30. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member through which the gases flow forming at least part of a gas passageway between said openings, and having an open area in the side walls thereof, means defining a sound trap chamber within said casing, separate from and at least partially around'said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appre ciably attenuate the noise of said sound entrained flowing gases and arranged so that little or none of said gases pass therethrough, the maximum effective cross sectional area of said tubular member being less than the maximum cross sectional area of said sound trap chamber.

31. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member of substantially uniform cross sectional area throughout its length through which gas flows forming at least part of a gas passageway between said openings, and having an open area in the side walls thereof, means defining a sound a trap chamber within said casing, separate from and at least partially around said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases and arranged so that little or none of said gases pass therethrough, the maximum effective cross sectional area of said tubular member being less than the maximum cross sectional area of said sound trap chamber.

32. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member forming at least part of a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures, means defining a sound trap chamber within said casing, separate from and at least partially around said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases and beingarranged so that little or none of said gases pass therethrough, the maximum effective cross sectional area of said tubular member being less than the maximum cross sectional area of said sound trap chamber.

33. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/ or exhaust system of an internal combustion I engine such as are used in motor vehicles, said noise comprising aconglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which" communicates with the cylinders of said engine, a tubular member forming at least part of a' gas passageway between said openings, andha'ving an open area in the side walls thereof; said open area comprising a plurality of 'relatively small apertures disposed along the length of said tubular member, means defining a sound trap chamber, separate from and at least partially around said passageway and acoustically coupled .thereto by means of said open area, said open LII of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member forming at least part of a gas passageway between said openings, and having an open area in the side walls thereof, said open area comprising a plurality of relatively small apertures disposed along the length and at least partially around said tubular member, means defining a sound trap chamber, separate from and at least partially around said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases and being arranged so that little or none of said gases pass therethrough.

, 35. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a tubular member through which gases flow forming at least part of a gas passageway between said openings, and having an open area in the side walls thereof, means defining a sound trap chamber, separate from and at least partially around said passageway and acoustically coupled thereto by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, at least part of said tubular member forming a part of said sound trap chamber defining means, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases and arranged so that littl or none of said gases pass therethrough.

36. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, means defining a plurality of sound trap chambers extending along the length and separate from said passage way, and within the casing, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open area in the side walls of said passageway, each of said open areas comprising a plurality of apertures disposed along the length of said passageway, each of said acoustic couplings providing a restricted communication from one of said sound trap chambers to said passageway and which communication operates to trap sound energy in said chamber, said sound trap'chambers being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

37. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, and means including transverse members defining a plurality of sound trap chambers extending along the length and separate from said passageway, and arranged at least partially around said passageway, each of said sound trap chambers being acoustically coupled to said passageway by means of an open area in the side walls of said passageway, at least one of said open areas comprising a plurality of apertures disposed along the length of said passageway, each of said open areas providing a restricted communication from one of said sound trap chambers to said passageway and which operates to trap sound energy in said chamber, said sound trap chambers being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

38. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches,

said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, means defining a plurality of sound trap chambers extending along the length and separate from said passageway, said sound trap chambers extending at least partially,

around said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open'area in the side walls of said passageway, each of said open areas providing a restricted communication from one of said sound trap chambers to said passageway and which communication operates to trap sound energy in said chamber, one of said open areas comprising a plurality of relatively small apertures disposed along the major portion of the length of that part of said passageway available for providing an acoustic coupling to one of said sound trap chambers, said sound trap chambers being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

39. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway be tween said openings, means defining a plurality of sound trap chambers extending along the length and separate from said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open area in the walls of said passageway, each of said open areas providing a restricted communication extending along the length of said passageway and from one of said sound trap chambers to said passageway and which communication operates to trap sound energy in said chamber, at least one of said open areas extending along the major portion of the length of that part of said passageway available for providing an acoustic coupling to one of said sound trap chambers, said sound trap chambers being abruptly enlarged adjacent said communication so as to permit rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

40. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, and means defining a plurality of sound trap chambers extending along the length and separate from said passageway, each of said sound trap chambers being acoustically coupled to said passageway by means of an open area in the side walls of said passageway, each of said open areas comprising a plurality of relatively small apertures disposed along the length and at least partially around said passageway and providing a restricted communication from one of said sound trap chambers to said passageway and which operates to trap sound energy in said chamber, said sound trap chambers being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases.

41. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, means defining a plurality of sound trap chambers separate from said passageway, acoustic coupling means providing restricted communication from said sound trap chambers to said passageway and which operates to trap sound energy in said chambers, said sound trap chambers being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, one of said chambers being arranged at least partially around said passageway and another of said sound trap chambers being located at one end I said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means including a tubular member of substantially uniform cross sectional area through which gases flow and defining a gas passageway between said openings, means defining a plurality of sound trap chambers extending along the length and separate from said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open area in the side walls of said passageway, each of said open areas comprising a plurality of apertures disposed along the length of said tubular member, each of said open areas providing a restricted communication from one of said sound trap chambers to said passageway and which communication operates to trap sound energy in said chamber, said sound trap chambers being abruptly enlarged adjacent said communications so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

43. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases, and provision for connecting one of said openings to a gas conducting member which, communicates with the cylinders of the engine, means defining a gas passageway within said casing between said openings, baflle means comprising a tubular member provided with perforations, said perforations forming at least a part of said passageway, means defining a sound trap chamber within said casing, separate from and acoustically coupled to said passageway, said acoustic coupling providing a restricted communication from said sound trap chamber to said passageway, said sound trap chamber being abruptly enlarged adjacent said communication to permit the rapid expansion of sound energy therein, and being disposed at least partially around said passageway. I

44. An acoustic silencer for silencing the noise of sound entrained flowing gases of the' intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases, and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway within said casing between said openings, means defining an expansion chamber and forming a part of said passageway, bafile means comprising a tubular member provided with perforations, through which gas flows from said expansion chamber to the interior of said tubular member on its way from said inlet to said outlet openings, means defining a sound trap chamber within said casing separate from and acoustically coupled to said passageway, said acoustic coupling providing a restricted communication from said sound trap chamber to said passageway, said sound trap chamber being abruptly enlarged adjacent said communication to permit the rapid expansion of sound energy therein, 'and being disposed at least partially around said passageway.

45. An acoustic silencer for silencing the noise of sound entrained flowing gases of intake and/ or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between said openings, means defining a plurality of sound trap chambers separate from said passageway, acoustic coupling means providing a separate restricted communication from each of said sound trap chambers to said passageway and said communications operating to trap sound energy in said chambers, one of said chambers decreasing in cross sectional area progressively with the distance from a zone adjacent its coupling to the closed end of said chamber, said sound .trap chambers being abruptly enlarged adjacent said communication and operating to oppreciably attenuate the noise of said sound entrained flowing gases.

46. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between said openings, means defining a plurality of sound trap chambers separate from said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open area in the walls of said passageway, each of said acoustic couplings providing a restricted communication to trap sound energy in said chamber, said sound trap chambers being abruptly enlargedadjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases, one of said open areas comprising a plurality of relatively small apertures and another of said acoustic couplings comprising a different type of open area.

47. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration'of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between sound trap chambers separate from said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open area in the walls of said passageway, each of said acoustic couplings providing a restricted communication from one of said sound trap chambers to said passageway and which communication operates to trap sound energy in said chamber, said sound trap chambers being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of said sound entrained flowing gases, one of said acoustic couplings comprising a plurality of relatively small openings and another of said acoustic couplings comprising an open area formed in a wall arranged transversely of the silencer and closing one side of one of said chambers.

48. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitchas, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a hollow member through which gas flows within said casing forming at least part of a gas passageway between said openings, a tubular member disposed between and in spaced relation with said casing and said hollow member and cooperating with at least a part of said casing to define a sound trap chamber, separate from said passageway, acoustic coupling means comprising a plurality of relatively small apertures extending along the length and at least partially around one of said members and providing at least part of a restricted communication from said chamber to said passageway, said communication operating to trap sound energy in said chamber.

49. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of the engine, perforated hollow members arranged within said casing and forming at least part of a gas passageway between said openings, one of said 'hollow members being disposed at least partly,within and spaced from the other of said members, one of said hollow members cooperating with at least a part of said casing to define a sound trap chamber, the perforations in said last mentioned hollow member forming an acoustic coupling and providing a restricted communication from said chamber to said passageway, said communication operating to trap sound energy in said chamber.

50. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a, hollow member through which gas flows within said casing forming at least part of a gas passageway between said openings, a tubular member disposed between and in spaced relation with said casing and said hollow member and cooperating with at least a part of said casing to define a sound trap chamber, separate from said passageway, one of said members being provided with a plurality of relatively small apertures in the walls thereof, acoustic coupling means comprising said plurality of relatively small apertures providing restricted communication from said chamber to said passageway, said communication operating to trap sound energy in said chamber, and a member extending transversely of said casing defining a part of said sound trap chamber and cooperating with a part of said casing to define another sound trap chamber which is acoustically coupled to said passageway by means which include a restricted opening in said transversely extending member, said sound trap chambers being constructed and arranged so as to permit rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases. I

51. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a hollow member through which gas flows within said casing forming at least part of a gas passageway between said openings, a tubular member disposed between and in spaced relation with said casing and said hollow member and cooperating withat least a part of said casing to define a sound trap chamber, separate from said passageway, acoustic coupling means comprising an open area in the side wall of at least one of said members providing restricted communication from said chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being constructed and arranged so as to permit rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

52. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, a hollow member through which gas flows within said casing forming at least part of a gas passageway. between said openings, a tubular member disposed between and in spaced relation with said casing and said hollow member and cooperating with at least a part of said casing to define a sound trap chamber separate from said passageway, one of said members being provided with a plurality of relatively small apertures in the walls thereof, acoustic coupling means comprising said plurality of relatively small apertures providing restricted communaction from said chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being constructed and arranged so as to permit rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

53. An acoustic silencer for silencing the noise of sound entrainedfiowin g gases of the intake and/or exhaust system of an internal combustion ing at least part of a gas passageway between hollow'member and'cooperating with at least a part of said casing to define a sound trap chamber, separate from said passageway, acoustic coupling means providing restricted communication from said chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being constructed and arranged so as to permit rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

54. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases, and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway within said casing between said openings, baffle means comprising a member provided with perforations, said perforations forming a part of said passageway, means defining a sound trap chamber within said casing,'a tubular member forming a part of said passageway and extending through said sound trap chamber, said sound trap chamber being acoustically coupled to said tubular member by means of an open area in the side walls thereof, said open area providing a -restricted communication from said sound trap chamber to the interior of said tubular member, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein. 7

.55. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust systempf an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases, and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway within said casing between said openings, baffle means comprising a tubular member provided with perforations, said perforations forming at least a part of said passageway,'means defining an expansion chamber forming a part of said passageway, means defining a sound trap chamber within said casing, separate from and acoustically coupled directly to said expansion chamber, said acoustic coupling providing a restricted communication from said sound trap chamber to said expansion chamber, said sound trap chamber being abruptly enlarged adjacent said communication to permitthe rapid expansion of sound energy therein.

56. An acoustic silencer for silencing the noise of sound entrained flowing gases of theintake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between said openings, means defining a plurality of sound trap chambers separate from said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open area in the walls of said passageway, each of said acoustic couplings providing a restricted communication from one of said sound trap chambers to saidpassageway and which communication operates to trap sound energy in said chambers, said sound trap chambers being abruptly enlarged adjacent said communication and operating to appreciably attenuate the noise of. said sound entrained flowing gases, one of said chambers being formed at least in part by spaced curved walls and the other of said sound trap chambers being formed at least in part by spaced transversely extending walls.

57. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, means defining a plurality of sound trap chambers separate from said passageway, acoustic coupling means providing 1'8,- stricted communication from said sound trap chambers to said passageway and which operates to trap sound energy in said chambers, said sound trap chambers being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, one of said chambers being arranged at least partially around said passageway and another of said sound trap chambers being located at one end of said silencer, the acoustic coupling for said one of said chambers comprising a plurality of relatively small apertures disposed along the length of said passageway.

58. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for con-, necting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, meansldefining a plurality of sound trap chambers extending along the length and separate from said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open area in the side walls of said passageway, at least one of said open areas comprising a plurality of apertures disposed along the length of said passageway, each of said acoustic couplings providing a restricted communication from one of said sound trap chambers to said passageway and which communication operates to trap sound energy in said chamber, said sound trap chambers being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

59. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a gas passageway between said openings, means defining a plurality of sound trap chambers extending along the length and separate from said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an open area in the side walls of said passageway, at least one of said open areas comprising a plurality of apertures disposed along the length of and at least partially around said passageway, each of said acoustic couplings providing a restricted communication from one of said sound trap chambers to said passageway and which communication operates to trap sound energy in said chamber, said sound trap chambers being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

60. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/ or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means defining a as passageway between said openings, means defining a plurality of sound trap chambers extending along the length and separate from said passageway, one of said chambers extending at least partially around said passageway, an acoustic coupling between each of said chambers and said passageway, each of said acoustic couplings comprising an 'open area in the side walls of said passageway, each of said open areas comprising a plurality of apertures disposed along the length of said passageway, each of said acoustic couplings providing a restricted communication from one of said sound trap chambers to said passageway and which communication operates to trap sound energy in said chamber, said sound trap chambers being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases.

61. An acoustic silencer for silencing the noise -tion engine such as are used in of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision tor connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means including an expansion chamber and a gas conducting member in gas flow relationship with said expansion chamber, defining a gas passageway between said openings and within said casing, means defining a sound trap chamber separate from said passageway, said sound trap chamber having an open area in the wall thereof, said sound trap chamber being acoustically coupled to the passageway by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication, said gas conducting member extending between said expansion chamber and one of said openings and forming a gas conduit through said sound trap chamber.

62. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means including two expansion chambers and a hallow member within said casing for conducting gases between said expansion chambers, and defining a gas passageway between said openings and within said casing, one of said expansion chambers having an open area in the walls thereof, and means defining a sound trap chamber separate from said passageway, said sound trap chamber being acoustically coupled to the expansion chamber by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, and a conduit forming a part of said gas passageway, connected to one of said openings and extending through said sound trap chamber.

63. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/0r exhaust system of an internal combusmotor vehicles, said noise comprising a conglomeration .of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means including two expansion chambers and a hollow member within the casing for conducting gases between said expansion chambers, and defining a gas passageway between said openings and withi in said casing, one of said expansion chambers having an open area in the walls thereof, and

means defining a sound trap chamber separate from said passageway,,said sound trap chamber being acoustically coupled to the expansion chamber by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in ,said

gas conducting member which communicates with the cylinders of the engine, means including an expansion'chamber defining a gas passageway between said openings and within said casing, said expansion chamber having an open area in the walls thereof, and means defining a sound trap chamber separate from said passageway, said sound trap chamber being acoustically coupled to the expansion chamber by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, a gas conducting member forming a part of said gas passageway and extending between said expansion chamber and one of said openings, and means defining another sound trap chamber acoustically coupled to said passageway independently of said open area.

65. An acoustic silencerior silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration of pitches, said silencer comprising a casing having inlet and outlet openings for said gases and provision for connecting one of the openings to a gas conducting member which communicates with the cylinders of the engine, means including an expansion chamber defining a gas passageway between said openings and within said casing, said expansion chamber having an open area in the walls thereof, and means defining. a

sound trap chamber separate from said passageway, said sound trap chamber being acoustically coupled to the expansion chamber by means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway which operates to trap sound energy in said chamber, a member forming a part of said gas passageway and extending between said expansion chamber and I one of said openings and passing through said sound trap chamber, and means defining another sound trap chamber acoustically coupled to said passageway independently of said open area.

66. An acoustic silencer for silencing the noise" 01! sound entrained flowing gases of the intake and/or exhaust system'of an internal combustion engine such as are used in,motor vehicles, said noise comprising a conglomeration of pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting memberwhicb communicates with the cylinders of said engine, means defining a gas passageway betweensaid openings, and having an open area comprising a plurality of relatively small apertures in the means of said open area, said open area providing a restricted communication from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent. said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, the maximum cross sectional area of said cham ber being materially greater than the maximum cross sectional area of said passageway.

67. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used in motor vehicles, said noise comprising a conglomeration 01 pitches, said silencer having inlet and outlet openings for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means including a hollow member defining a gas passageway between said openings, an open area in the side walls of said hollow member, means defining a sound trap chamber, separate from said passageway and arranged around said hollow member, said sound trap chamber being acoustically coupled to said passageway by means of said open area, said open area providing a restricted communication" from said sound trap chamber to said passageway, said communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said sound entrained flowing gases, the'maximum cross sectional area of said chamber being materially greater than the maximum cross sectional area'of said hollow member.

68. An acoustic silencer for silencing the noise of sound entrained flowing gases of the intake and/or exhaust system of an internal combustion engine such as are used ,in motor vehicles, said noise comprising a conglomeration of pitches,

' said silencer having inlet and outlet openings side walls thereof, means defining a sound trap chamber, separate from and arranged around said passageway, said sound trap chamber being acoustically coupled to said passageway by for said gases and provision for connecting one of said openings to a gas conducting member which communicates with the cylinders of said engine, means defining a gas passageway between said openings, and having an open area in the side walls thereof, means defining a sound trap chamber, separate from and arranged at least partially around said passageway, said sound trap chamber being acoustically coupled to said passageway by means of said open area, said open area'providing a restricted communication Irom said sound trap chamber to said passageway, sa id communication operating to trap sound energy in said chamber, said sound trap chamber being abruptly enlarged adjacent said communication so as to permit the rapid expansion of sound energy therein and operating to appreciably attenuate the noise of said soundbntrairied flowing gases, the maximum transversemross sectional area subtended by the outer periphery of the means defining said passageway 6n 9. plane pass- CARL F. RAUEN