Technical Field The present invention relates to a constricted tube structure which may be used as part of a device for sound suppression, such as a muffler, tail pipe or connecting pipe.

Background of the Invention Typical vehicle exhaust systems include an exhaust pipe, a muffler, and a tail pipe. In prior systems, acoustic attenuation, or sound suppression, is substantially performed by the muffler, while the connecting pipe and the tail pipe serve primarily to transport the exhaust gas. These pipes are typically cylindrical tubes of constant cross-sectional area and may include an elbow bend or a T-shaped intersection. In some instances, the pipes themselves may add to the noise problem by creating standing waves and undesirable resonances.

Generally, a muffler's attenuating influence is related to its length and diameter; the larger a muffler is, the greater its attenuating influence. To attenuate low frequency noise, such as that produced in a truck exhaust system, a muffler must be relatively long.

Relatively long or large mufflers, however, are disadvantageous for many reasons. Long or large mufflers require a relatively large amount of steel to manufacture and therefore are relatively expensive to produce. They are relatively heavy and cumbersome and therefore relatively difficult to install and. support. Perhaps most significant is that the vehicle must include a relatively large space dedicated to a relatively large muffler, thus necessitating redesign of engine placement and body design to accommodate.

One" highly effective means of suppressing sound is the employment of an apparatus including a venturi contained within a housing. Such an apparatus is shown in U.S. Patent No. 4,580,657.

It would be desirable to produce a venturi-like sound attenuating element of a reasonable size, which has relatively good sound suppression characteristics. Further, it would be desirable to create attenuating elements capable of serving as tail pipe or connecting pipe sections thus requiring less attenuating at the muffler to achieve a given attenuation which is distributed through the system as a whole.

Summary of the Invention

The present invention is directed to a sound- suppressing device having inlet and outlet ends and a constricted portion therebetween.

According to another aspect of this invention, the constricted portion has a cross-sectional area at one end substantially similar to the inlet cross- sectional area. The constricted portion cross-sectional area decreases relatively rapidly to a minimum area at a point of maximum constriction and, downstream of the constriction, increases more gradually to an area substantially similar to the outlet cross-sectional area.

According to a another aspect of the invention, the constricted portion includes an angular bend. According to another aspect of this invention, the sound-suppressing device includes a tubular attenuating element within a tubular housing.

According to a further aspect of this invention, the tubular attenuating element includes an constricting member suspended within a tubular housing, where the housing may be an attenuating element.

The specifications and drawings disclose numerous embodiments. However, the invention is characterized in the claims annexed hereto and forming a part hereof. For a better understanding of the invention, its advantages and objects obtained by its use, reference should be made to the drawings and

accompanying descriptive matter.

Brief Description of the Drawings Figure 1 is a perspective view of an attenuating element disposed in a tubular housing; Figure 2 is a side elevational view of the attenuating element in Figure 1;

Figure 3 is an inlet end view as seen from the left end of the tube in Figure 1; Figure 4 is an outlet end view as seen from the right end of the tube in Figure 1;

Figure 5 is a perspective view of an alternate embodiment of an attenuating element;

Figure 6 is an outlet end view as seen from the right end of the element in Figure 5;

Figure 7 is an inlet end view as seen from the left end of the element in Figure 5;

Figure 8 is an elevational view of the element shown in Figure 5; Figure 9 is a side elevational view of the element in Figure 5;

Figure 10 is a perspective view of an alternate embodiment of an attenuating element;

Figure 11 is an inlet end view as seen from the left end of the attenuating element in Figure 10;

Figure 12 is an outlet end view as seen from the right of the attenuating of Figure 10;

Figure 13 is a side elevational view of the element in Figure 10; Figure 14 is a side elevational view of an alternate embodiment of an attenuating element;

Figure 15 is a perspective view of an alternate embodiment of attenuating elements;

Figure 16 is a side elevational view of the element in Figure 15;

Figure 17 is an elevational view of the em¬ bodiment of the attenuating element shown in Figure 15;

Figure 18 is a side elevational view as seen from the right side of the element shown in Figure 16;

Figures 19a-g are shape patterns taken along lines A-G, respectively, in Figure 16; Figure 20 is a perspective view of an alternate embodiment of an attenuating element;

Figure 21 is a side elevational view of the element in Figure 20;

Figure 22 is a top elevational view of the embodiment of an attenuating element shown in Figure 20;

Figures 23a-g are shape patterns taken along lines A-G of Figure 21;

Figure 24 is a side elevational view as seen from the right side of the element in Figure 21; Figure 25 is a perspective view of an alternative attenuating element to be used to divide a single exhaust pipe into a dual exhaust pipe;

Figure 26 is a side elevational view of the element in Figure 25; Figure 27 is a cross-sectional view taken along lines 51-51 of Figure 26;

Figure 28 is an outlet end view as seen from the left side of the element in Figure 25;

Detailed Description of the Invention

I. CIRCULAR RESONATOR EMBODIMENT A first embodiment of a constricted attenuating member 3 is a circular attenuating member 10, shown in Figures 1-4. Circular attenuating member 10 has an inlet end 11 and an outlet end 12, an includes an inner surface 13a and an outer surface 13b. Inner surface 13a defines a channel 14 and has a first end portion 15, a second end portion 16, and a constricted portion 20 therebetween. Constricted portion 20 includes a converging portion 22, a diverging portion 23, and a throat portion 25, therebetween. Throat portion 25 has a generally circular periphery and includes a point of

greatest constriction 26.

Converging portion 22 is characterized by a region of rapidly decreasing throat cross-sectional area 27, where the cross-sectional area decreases in the direction from first end portion 15 to the point of greatest constriction 26. Diverging portion 23 is characterized by a region of gradually increasing cross- sectional area 28 where the cross-sectional area increases in the direction from the point of greatest constriction 26 toward second end portion 16. The terms "rapid" and "gradual", as used throughout, are relative terms with respect to each other.

First end portion 15 includes a tubular member 30 having an inner surface 31 and an outer surface 32. Inner surface 31 is generally cylindrical; that is, inner surface 31 is generally circular in cross-section with a constant diameter 35 along the length of inner surface 31 in the direction indicated by arrow 37. (Arrow 37 designates the general direction of flow of a fluid through the attenuating member 10, as will be discussed below. ) Outer surface 32 is also generally cylindrical and parallel to inner surface 31; that is, outer surface 32 is generally circular in cross-section with a constant diameter 39 along the length of outer surface 32 in the direction indicated by arrow 37.

Converging portion 22 includes a tubular member 40 having an inner surface 41 and an outer surface 42. Inner surface 41 is convexly curved; that is, inner surface 41 is generally circular in cross section, with a relatively rapidly decreasing diameter along the length of inner surface 41 in the direction indicated by arrow 37. Outer surface 42 is generally parallel to inner surface 41; that is, outer surface 42 is generally circular in cross-section with a relatively rapidly decreasing diameter along the length of outer surface 42 in the direction indicated by arrow 37.

Throat portion 25 includes a tubular member 45

having an inner surface 46 and an outer surface 47. Inner surface 46 is generally circular in cross section and includes a region 48 of least cross-sectional area. Similarly, outer surface 47 is generally circular in 5 cross section and includes a region 49 of least cross- sectional area.

Diverging portion 23 similarly includes a tubular member 50 having an inner surface 51 and an outer surface 52. Inner surface 51 is generally

10 conical; that is, inner surface 51 is generally circular in cross-section with a relatively gradually increasing diameter along the length of inner surface 51 in the direction indicated by arrow 37. Outer surface 52 is generally parallel to inner surface 61 and therefore is

15. generally conical; that is, outer surface 52 is generally circular in cross-section with a relatively gradually increasing diameter along the length of outer surface 52 in the direction indicated by arrow 37.

In the preferred circular attenuating member

20 10, converging portion 22 includes a point 53 of greatest cross-sectional area. Converging portion inner surface 41 includes a corresponding point 53a of greatest cross-sectional area; similarly, converging portion outer surface 42 includes a corresponding point

25 53b of greatest cross-sectional area.

Diverging portion 23 includes a point 54 of greatest cross-sectional area. Diverging portion inner surface 51 includes a corresponding point 54a of greatest cross-sectional area; similarly, diverging

30 portion outer surface 52 includes a corresponding point 54b of greatest cross-sectional area. Preferably, point 54b has a cross-sectional area which may be less the cross-sectional area of point 53b.

Preferred converging portion 22 converges at an

35 angle or slope generally greater than the angle or slope at which the diverging portion 23 diverges. Angle, as used throughout, is synonymous with slope. Diverging

portion 23 diverges at an angle or slope less than that which produces flow separation, which is generally between about 7 ° and 14 ; that is, an angle 56 of between 3.5° and 7 ^° is defined between diverging portion 23 and longitudinal axis 57. It should be noted that angles as specified throughout are preferable for use in many exhaust systems; the angle required to optimize attenuation may vary according to the exhaust system in which the element is used, and therefore the range of angles specified should not be considered limiting.

Preferably, second end portion 16 includes a perforated portion 58 having perforations 59 as shown in Figures 6 and 7. Perforations 59 may be generally circular and may be arranged in rings 59a about diverging portion 23 generally proximate second end portion 16.

In typical use, the attenuating member 10 with perforations 56 is suspended in a tubular housing section 70 of an exhaust system. Tubular section 70 defines a channel portion 71 and may be a portion of a tail pipe, an exhaust pipe, or a muffler. Tubular section 70 includes an inlet portion 75 and an outlet portion 76.

Tubular section 70 has an inner surface 72. Inner surface 72 is generally cylindrical; that is, inner surface 72 is generally circular in cross-section with a generally constant cross-sectional area along the length of inner surface 72 in the direction indicated by arrow 37. Generally, the cross-sectional area of point

53b of attenuating member 10 is approximately equal to the cross-sectional area of inner surface 72. The cross-sectional area of point 54b of attenuating member 10 is slightly less than the cross-sectional area of inner surface 72.

An annular cavity or chamber 80 is defined - generally between attenuating member 10 and tubular

section 70. Annular cavity 80 includes a diverging portion 85 and a converging portion 86. Cavity diverging portion 85 is defined between tubular member converging portion outer surface 42 and tubular section inner surface 72. Annular cavity 80 includes a point 88 of greatest cross-sectional area defined between tubular member outer surface point 49 and tubular section inner surface 72. Cavity converging portion 86 is defined between tubular member diverging portion outer surface 52 and tubular section inner surface 72.

Attenuating member channel 14 is in fluid communication with annular cavity 80 through perforations 59.

An annular gap 95 is defined between the point 54b of greatest cross-sectional area of diverging portion outer surface 52 and tubular section 70. Annular cavity 80 and channel portion 71 are in fluid communication through annular gap 95. It is found that greater attenuation is achieved with the above-described configuration of perforations 59 and annular gap 45 than can be achieved with perforations alone. The gap and perforations arrangement forms a resonator which aids attenuation of noise.

II. SCOOP RESONATOR EMBODIMENT

A third embodiment of constricted attenuating member 3 is a scoop attenuating member 210, shown in Figures 5-9. Scoop attenuating member 210 has an inlet end 211 and an outlet end 212, and includes an inner surface 213a and an outer surface 213b. Inner surface 213a defines a channel 214 and has a first end portion 215, a second end portion 216, and a constricted portion 220 therebetween. Constricted portion 220 includes a converging portion 222, diverging portion 223 and a throat portion 225 therebetween. Throat portion 225 includes a point of greatest constriction 226.

As shown in Figure 9, converging portion 222 is

characterized by a region of rapidly decreasing throat cross-sectional area 227, where the cross-sectional area decreases in the direction from the first end portion 215 to the throat portion 225. Diverging portion 223 is characterized by a region of gradually increasing cross- sectional area 228, where cross-sectional area increases in the direction from the point of greatest constriction 226 toward the second end portion 216.

First end portion 215 includes a generally cylindrical tubular member 229 defining a channel portion 230. Cylindrical tubular member 229 has an inner surface 231 and an outer surface 232. Inner surface 231 is generally cylindrical; that is, inner surface 231 is generally circular in cross-section with a constant diameter along the length of inner surface

231 in the direction indicated by arrow 233. (Arrow 233 designates the general direction of flow of a fluid through the attenuating member 210, as will be discussed below. ) Second end portion 216 includes a generally cylindrical tubular member 234 defining a channel portion 234a. Cylindrical tubular member 234 has an inner surface 235 and an outer surface 236 generally parallel to inner surface 235. Inner surface 235 is generally cylindrical; that is, inner surface 235 is generally circular in cross section with a constant diameter along the length of inner surface 235 in the direction indicated by arrow 233.

Constricted portion 220 includes a generally cylindrical tubular member 237 and a contoured constricting member 238. Tubular member 237 includes an inner surface 239. Constricting member 238 includes a concave curved member 240, and a diverging planar member 241. Concave curved member 240 may be immediately adjacent diverging planar member 241; alternatively, there may be a planar throat member 242 between concave curved member 240 and diverging planar member' 241, as

shown in Figures 16-20.

Concave curved member 240 has an inner surface 245 and an outer surface 246, generally parallel to inner surface 245. Diverging planar member 241 has an inner ^" surface 248 and an outer surface 249, generally parallel to inner surface 248. Planar member 242 includes an inner surface 251 and an outer surface 252, generally parallel to inner surface 251.

A converging channel portion 255 is defined by concave curved member inner surface 245 and tubular member inner surface 239. A diverging channel portion 256 is generally defined by diverging planar member inner surface 248 and tubular member inner surface 239. A channel portion 257 of greatest constriction is defined by planar throat member inner surface 251 and cylindrical tubular member inner surface 239. Converging channel portion 255 has a point 260 of greatest cross-sectional area, substantially equal to the cross-sectional area of channel portion 230. Diverging channel portion 256 includes a point 261 of greatest cross-sectional area having a cross-sectional area slightly less than the cross-sectional area of converging channel portion point 260.

Diverging planar member 251 preferably defines an angle 262 with longitudinal axis 263 of not more than about 14" . Separation of the flow may result in the diverging portion 223 if angle 262 is substantially greater than 14". Separation of the flow will cause increased back pressure which may be undesirable in a particular exhaust system since increased back pressure may reduce engine efficiency.

Diverging planar member 251 may include a perforated portion 265 having perforations 266. Perforations 366 are preferably generally circular. The total cross-sectional area of these perforations are dependent on the frequency band of noise to be attenuated by the device.

Typically, contoured constricting member 238 is suspended in a tubular housing section 270 such that a portion of tubular housing section 270 forms cylindrical tubular member 237. This arrangement is best shown in Figure 20.

Tubular section 270 defines a channel portion 271 and may be a portion of a tail pipe, a connecting pipe, or a muffler. The tubular section 270 has an inner surface 272 and includes an inlet portion 275 and an outlet portion 276.

A cavity or chamber 280 is generally defined between the attenuating member 210 and the tubular section 270. Annular cavity 280 includes a diverging cavity portion 285, a converging cavity portion 286 and a point of cavity greatest cross-sectional area 288. Diverging cavity portion 285 is generally defined between tubular section inner surface 272 and concave curved member outer surface 246. Converging cavity portion 286 is generally defined between tubular section inner surface 272 and diverging planar member outer surface 249. Converging cavity portion 286 includes a point of least cross-sectional area 287. Point of cavity greatest cross-sectional area 288 is defined between tubular member inner surface 239 and planar throat member outer surface 252.

Attenuating member channel 214 is in fluid communication with cavity 280 through perforations 266.

A gap 295 is defined between tubular section inner surface 272 and diverging planar member outer surface 249 at converging cavity portion point of least cross-sectional area 287. Cavity 280 and channel portion 271 are in fluid communication through gap 295. It is found that greater attenuation is achieved with the above-described configuration of perforations 266 and gap 295 than can be achieved with perforations alone. The gap and perforations arrangement forms a - resonator which aids attenuation of noise.

A fourth embodiment of a constituted attenuating member 3 is a double-scoop constricted attenuating member 310, as shown in Figures 10-14. Attenuating member 310 has an inlet end 311 and an outlet end 312, and includes an inner surface 313a and an outer surface 313b. Inner surface 313a defines a channel 314 and has a first end portion 315, a second end portion 316, and a constricted portion 320 therebetween. Constricted portion 320 includes a converging portion 322, a diverging portion 323, and a throat portion 325 therebetween. Throat portion 325 includes a point of greatest constriction 326.

As seen in Figure 13, the converging portion 322 is characterized by a region of rapidly decreasing throat cross-sectional area 327, where the cross- sectional area decreases in the direction from the first end portion 315 to the point of greatest constriction 326. The diverging portion 323 is characterized by a region of gradually increasing cross-sectional area 328 where the cross-sectional area increases in the direction from the point of greatest constriction 326 toward the second end portion 316.

First end portion 315 includes a generally cylindrical member 329 defining a channel portion 330. Cylindrical member 329 has an inner surface 331 and an outer surface 332. Inner surface 331 is generally cylindrical; that is, inner surface 331 is generally circular in cross-section with the constant diameter along the length of inner surface 331 in the direction indicated by arrow 333.

Second end portion 316 includes a cylindrical member 334. Cylindrical tubular member 334 has an inner surface 335 and an outer surface 336. Inner surface 335 is generally cylindrical; that is, inner surface 335 is generally circular in cross-section with the constant diameter along the length of inner surface 335 in the direction indicated by arrow 333.

Constricted portion 320 includes a generally cylindrical tubular member 337 and two contoured constricting members 338a,b. Description follows of contoured constricting member 338a. It is to be understood that contoured constricting member 338b is substantially similar to member 338a.

Constricting member 338a includes a concave curved member 340, diverging planar member 341, and a planar throat member 342 therebetween. Concave curved member 340 has an inner surface 345 and an outer surface 346, generally parallel to inner surface 345. Diverging planar member 341 has an inner surface 348 and an outer surface 349, generally parallel to inner surface 348. Planar member 342 includes an inner surface 351 and an outer surface 352, generally parallel to inner surface 351.

A converging channel portion 355 is defined by concave curved member inner surfaces 345a,b and tubular member inner surface 339. A diverging channel portion 356 is generally defined by diverging planar member inner surfaces 348a,b and tubular member inner surface 339. A channel portion 357 of greatest constriction is defined by planar throat member inner surface 351 and cylindrical tubular member inner surface 339. Converging channel portion 355 has a point 360 of greatest cross-sectional area, substantially equal to the cross-sectional area of channel portion 330. Diverging channel portion 356 includes a point 361 of greatest cross-sectional area. Diverging planar members 341a,b preferably define an angle 362, therebetween, of 4-8°. The optimal angle 362 is dependant upon the back pressure acceptable for the engine with which attenuating element 310 is used. The greater the angle 362 is, the greater likelihood that the flow through channel portion 356 will separate. This separation of flow may cause increased back pressure which may reduce engine

efficiency and may also increase noise. As noted above, increased back pressure may reduce engine efficiency.

Typically, contoured constricting members 338a and 338b are suspended in a tubular housing section 370 having an inner surface 370a, such that a portion of tubular housing section 370 forms cylindrical tubular member 337. This arrangement is best shown in Figure 24.

Tubular section 370 defines a channel portion 371 and may be a portion of a tail pipe, an exhaust pipe, or a muffler. The tubular section 370 includes an inlet portion 375 and an outlet portion 376.

A cavity or chamber 380 is generally defined between the attenuating member 310 and the tubular section 370. Cavity recess 380 includes a diverging . cavity portion 385, a converging cavity portion 386 and a point of cavity greatest cross-sectional area 388 therebetween. Diverging cavity portion 385 is generally defined between tubular section inner surface 370a and concave curved member outer surface 346. Converging cavity portion 386 is generally defined between tubular section inner surface 370a and diverging planar member outer surface 349. Converging cavity portion 386 includes a point of least cross-sectional area 387. Point of cavity greatest cross-sectional area 388 is defined between tubular section inner surface 370a and planar throat member outer surface 352.

As shown in Figure 14, converging cavity portion point of least cross-sectional area 387 may have a cross-sectional area less than the cross-sectional area of tubular section inner surface 370a, such that a gap 395 is formed between diverging planar member 341 and tubular section inner surface 370a. The gap allows cavity 380 to be in fluid communication with diverging channel portion 356. Further, diverging planar members may include perforated portions 396 perforations 397 allowing diverging channel portion 356 to be in fluid

communication with cavity 380. This gap and perforation arrangement forms a resonator which aids attenuation of noise.

III. ELBOW ELEMENT EMBODIMENT

A further embodiment of a constricted attenuating element 3 is an elbow constricted attenuating member 710 as shown in Figures 15-19. Elbow attenuating member 710 preferably is integral with a tail pipe, connecting pipe, or muffler. Attenuating member 710 has an inlet end 711 and an outlet end 712, and includes an inner surface 713a and an outer surface 713b. Inner surface 713a defines a channel 714 and has a first end portion 715, a second end portion.716 and a constricted portion 720 therebetween. .

Constricted portion 720 includes a converging portion 722, a diverging portion 723, and a throat portion 724 therebetween. Throat portion 724 includes a point of greatest constriction 725. Member 710 has a substantially constant circumference along its length. The shape of the periphery of member 710 is generally represented by peripheral patterns 726a-g shown in Figures 19a-g, respectively, corresponding to cross- sections A-G, respectively, indicated in Figure 16. Patterns 726b-f are generally crescent-shaped and include a bottom portion 727b-f and a top portion 728b- f. A greater cross-sectional area is defined by peripheral pattern 726c than is defined by peripheral pattern 726g. Further, a greater cross-sectional area is defined by peripheral pattern 726g than is defined by peripheral pattern 726c.

The converging portion 722 is characterized by a region of rapidly decreasing throat cross-sectional area 729, where the cross-sectional area decreases in the direction from the first end portion 715 to the throat portion 724. The diverging portion 723 is characterized by a region of gradually increasing cross-

sectional area 729a, where cross-sectional area increases in the direction from the point of greatest constriction 726 toward the second end portion 716.

First end portion 715 includes a tubular member 730 having an inner surface 731 and an outer surface 732 generally parallel to inner surface 731. Inner surface 731 is generally cylindrical; that is, inner surface 731 is generally circular in cross-section with a constant diameter along the length of inner surface 731 in the direction indicated by arrow 737. (Arrow 737 designates the general direction of flow of a fluid through the attenuating member 710, as will be discussed below.) Pattern 726a, Figure 19a, represents the shape of inner surface 731 at cross-section A shown in Figure 16. Converging portion 722 includes a tubular member 740 having an inner surface 741 and an outer surface 742 generally parallel to inner surface 741. Pattern 726b, Figure 19b, represents the shape of inner surface 741 at cross-section B shown in Figure 16. Throat portion 724 includes a tubular member 750 having an inner surface 751 and an outer surface 752 generally parallel to inner surface 751. Pattern 726c, Figure 19c, represents the shape of inner surface 751 a cross- section C shown in Figure 16. Diverging portion 723 similarly includes a tubular member 760 having an inner surface 761 and an outer surface 762 generally parallel to inner surface 761.

Second end portion 716 includes a tubular member 770 having an inner surface 771 and an outer surface 772 generally parallel to inner surface 771. Surface 771 is generally cylindrical; that is, inner surface 771 is generally circular in cross-section with a constant diameter along the length of inner surface 771 in the direction indicated by arrow 776. Pattern 726g, Figure 19g, represents the shape of inner surface 771 at cross-section G shown in Figure 16.

Constricted portion 720 further includes an angular bend 780. The angular bend 780 as shown in Figures 15-19 is included in the converging portion 722; it is, however to be understood that the angular bend 780 may be included in the throat portion 724 or the diverging portion 723. Angular bend 780 defines an angle 781 between longitudinal axes 783 and 784, where longitudinal axis 783 is generally parallel to fluid flow through first end portion 715, and longitudinal axis 784 is generally parallel to fluid flow through second end portion 716. Angle 781 may be whatever is required by the structural design of the exhaust system.

A further embodiment of a constricted attenuating element 3 is an elbow constricted attenuating member 810, shown in Figures 20-24.

Attenuating member 810 has an inlet end 811 and an outlet end 812, and includes an inner surface 813a and an outer surface 813b. Inner surface 813a defines a channel 814 and has a first end portion 815, a second end portion 816, and a constricted portion 820 therebetween.

Constricted portion 820 includes a converging portion 822, a diverging portion 823, and a throat portion 824 therebetween. Throat portion 824 includes a point of greatest constriction 825. Attenuating member 810 has cross-sectional patterns 826a-g as shown in Figures 23a-g, taken at cross-sections A-G in Figure 21. Pattern 826a of first end portion is generally circular. Patterns 826b-f of the constricted portion 820 are generally oblong but vary in shape along the length of the attenuating member 810. Near first end portion 815, constricted portion pattern 826b is nearly circular. The cross-sectional pattern 826b, generally near the point of greatest constriction 825, is substantially oblong. A cross-sectional pattern 826f near second end portion 816 is nearly circular. The circumference of constricted portion 820 remains

constant throughout.

Converging portion 822 is characterized by a region of rapidly decreasing throat cross-sectional area

827, where the cross-sectional area decreases in the direction from the first end portion 815 to the throat portion 825. The diverging portion 823 is characterized by a region of gradually increasing cross-sectional area

828, where cross-sectional area increases in the direction from the point of greatest constriction 826 toward the second end portion 816.

First end portion 815 includes a tubular member

830 having an inner surface 831 and an outer surface 832 generally parallel to inner surface 831. Inner surface

831 is generally cylindrical; that is, inner surface 831 is generally circular in cross-section with the constant diameter along the length of inner surface 831 in the direction indicated by arrow 837. (Arrow 837 designates the general direction of flow of a fluid through the attenuating member 810, as will be discussed below.) Converging portion 822 includes a tubular member 840 having an inner surface 841 and an outer surface 842 generally parallel to inner surface 841. The shape of inner surface 841 is represented by pattern 826b, shown in Figure 23b, described above. Throat portion 824 includes a tubular member

850 having an inner surface 851 and an outer surface 852 generally parallel to inner surface 851. The shape of throat portion inner surface 851 is represented by pattern 826c, shown in Figure 23c, described above. Diverging portion 823 similarly includes a tubular member 860 having an inner surface 861 and an outer surface 862 generally parallel to inner surface 861. The shape of diverging portion inner surface 861 is represented by patterns 826d-f, shown in Figure 23d- f, described above.

Second end portion 816 includes a tubular member 870 having an inner surface 871 and an outer

surface 872 generally parallel to inner surface 871. Inner surface 871 is generally cylindrical; that is, inner surface 871 is generally circular in cross-section with the constant diameter along the length of inner surface 871 in the direction indicated by arrow 875.

(Arrow 875 designates the general direction of flow of a fluid through the attenuating member 810, as will be discussed below.)

Constricted portion 820 further includes an angular bend 880. The angular bend 880 as shown in

Figures 20-24 is included in the converging portion 822; it is, however to be understood that the angular bend 880 may be included in the throat portion 824 or the diverging portion 823. Angular bend 880 defines an angle 881 between longitudinal axes 883 and 884, where longitudinal axis 883 is generally parallel to fluid flow through first end portion 815, and longitudinal axis 884 is generally parallel to fluid flow through second end portion 816.

IV. SPLITTER ELEMENT EMBODIMENT An embodiment of a constricted attenuating member 3 which may be used in a dual exhaust system is a splitter attenuating member 1010, shown in Figures 25- 28. Attenuating member 1010 has an inner surface 1011 and an outer surface 1012 and includes a first inlet end portion 1013, at least two second outlet end portions 1014a,b, and a constricted portion 1015 therebetween. Constricted portion 1015 includes a converging portion 1016, a diverging portion 1017 and a throat portion 1018 therebetween. Throat portion 1018 includes a point of greatest constriction 1019.

Converging portion 1016 is characterized by a region of rapidly decreasing throat cross-sectional area 1020, where the cross-sectional area decreases in the direction from first end portion 1013 to the point of _ greatest constriction 1019. Diverging portion 1017 is

characterized by a region of gradually increasing cross- sectional area 1021 where the cross-sectional area increases in the direction from the point of greatest constriction 1019 toward second end portion 1014a,b. Constricted portion 1015 includes an outer tubular member 1022 and a contoured constricting member 1023. Constricting member 1020 has a first member 1024 with a similar second member 1025 joined thereto. First member 1024 is here described. It is to be understood that second member 1025 is substantially similar. Member 1024 includes a curved portion 1026 and may include a flat portion 1027. Member 1024 is substantially flat across its width. Curved portion

1026 includes a first portion 1029, a second portion 1030 and a third portion 1031. Third portion 1031 preferably has a perforated portion 1032 with perforations 1033, as shown in Figure 25. Flat portion

1027 includes recesses 1034.

The concave side of first member 1024 includes an inner surface 1035, and the convex side of first member 1024 includes an outer surface 1036, generally parallel to inner surface 1035.

Constricting member 1023 is disposed in a T- or Y-shaped tubular housing 1040 having a cylindrical inlet portion 1041 and at least two cylindrical outlet portions 1042a,b, and an intersection portion 1043, therebetween. Inlet portion 1041 has an inner surface 1044; outlet portions 1042a,b have inner surfaces 1045a,b, respectively, and intersecting portion 1043 has inner surface 1046. An inlet channel 1047 is defined by inlet portion inner surface 1044; outlet channels 1048a,b are defined by outlet portion inner surface 1045.

Constricted channels 1050a,b are generally defined between constricting member inner surfaces

1035a,b, and tubular housing 1040. A cavity or chamber 1052 is generally defined between outer surfaces 1036a,b

and tubular housing 1040. Channels 1050a,b are in fluid communication with cavity 1052 through perforations 1033. Cavity 1052 is in fluid communication with outlet channels 1048a,b through openings or apertures 1034. This arrangement of perforations and openings forms a resonator which aids noise attenuation.

Constricted channel 1050a will be here described. It is to be understood that constricted channel 1050b is substantially similar. Constricted channel 1050a includes a converging channel portion 1054, a diverging channel portion 1055, and a throat channel portion 1056 therebetween. Throat channel portion 1056, has a generally semi-circular periphery and includes a point of greatest channel constriction 1057.

Converging channel portion 1054 is defined between first portion 1029 of constricting member curved portion 1026 and tubular housing intersection inner surface 1046. Throat channel portion 1056 is defined between second portion 1030 of constricting member curved portion 1026 and tubular housing intersection inner surface 1046. Diverging channel portion 1055 is defined between third portion 1031 of constricting member curved portion 1026 and tubular housing intersection inner surface 1046.

Numerous characteristics and advantages of the invention have been set forth in the foregoing description, together with the details of the structure and function of the invention. The novel features thereof are pointed out in the claims. The disclosure, however, is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts, within the principle of the invention, to the full extent indicated by the broad general meanings of the terms in which the appended claims are expressed.