Abstract:
An intake combustion resonator including an enclosure which includes a resonator tube assembly passing through the enclosure. The resonator tube is formed from porous, undulated tube material and has openings formed in the tube walls. The openings serve as “tuned” passages through the porous tube walls. The resonator tube assembly is not centrally located within the enclosure but rather it is offset both in a height and a width orientation. The size, spacing, and orientation of the tube openings, porous, undulated sleeve material, the design of the enclosure, and the placement of the tube within the enclosure, all act in concert to give rise to the noise abatement properties of the present invention.

Description:
TECHNICAL FIELD 
   This invention generally relates to sound suppression devices and more particularly relates to resonators for attenuating sound produced by rotating machinery. 
   BACKGROUND OF THE INVENTION 
   It is generally desirable to minimize engine noise generated from internal combustion engines. Typically, this type of noise is reduced or minimized through the use of mufflers (for reducing combustion noise emitted from engine exhaust air) and the use of resonators (for attenuating the noise generated from the engine air intake system). 
   One common approach to attenuating noise emitted from the intake portion of an engine, is to use resonators constructed from one or more interior chambers which are “tuned” in a way which cancels certain frequency ranges of intake noise. However, tuned resonators involve many design compromises which, invariably, make them inefficient in reducing engine noise at “non-optimum” engine speeds. 
   A typical resonator includes an air reservoir comprising a fixed volume connected through a neck portion which leads to the intake manifold of an engine. Baffles, tubes and other “tuning” devices are also typically included in a resonator&#39;s design. The volume of the resonator and other component dimensions are determined based on numerous factors including sound characteristics desired by the customer, component packaging within the vehicle, the number of engine cylinders, engine size, and other engine and vehicle factors that influence noise volumes and noise frequencies emitted from the air handling system of an engine. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an environmental view showing the general environment in which the resonator of the present invention is used. 
       FIG. 2  is an isometric view of an embodiment of the resonator of the present invention. 
       FIG. 3  is a front elevational view of the resonator of FIG.  2 . 
       FIG. 4  is an exploded view of the porous tube of FIG.  2 . 
       FIG. 5  is a graphical depiction of the noise transmission loss evidenced by the resonator of the present invention, as compared with a simple slot resonator and also as compared with a simple porous duct attenuator. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a general environmental view showing the intake combustion resonator  10  of the present invention in the environment in which it typically operates. Specifically, the intake combustion resonator  10  of the present invention is designed to reside between the intake air filter  12  and the throttle body  14  of internal combustion engine  16 . It is to be understood that although  FIG. 1  depicts the typical placement of intake combustion resonator  10  with respect to intake air filter  12 , throttle body  14 , and internal combustion engine  16 , it is to be understood that many other arrangements of these components could be made without effecting the operation of the present invention. For example, combustion resonator  10  could reside between the air intake filter and the intake duct. 
   Now referring to  FIGS. 1 and 2 , intake combustion air resonator  10  is comprised of two primary components—enclosure  18 , and porous tube element  20 . End portions  22 ,  22 ′ of tube element  20  extend through opposing sides  24 ,  26  of enclosure  18 . End portions  22 ,  22 ′ of tube element  20  are sealed  28 ,  28 ′ at respective openings  11 ,  13  through opposing sides  24 ,  26  of enclosure  18 . Sealing  28 ,  28 ′ can be accomplished by any numerous means well known to those skilled in the art, including the use of adhesives, resins, epoxy, plastic filler, welding, soldering, mechanical fitting, mechanical clamping or the like. Also, it is possible to fabricate end portions  22 ,  22 ′ of tube  20  and openings  11 ,  13  of enclosure  18  using sufficiently tight tolerances such that an effective seal is obtained by way of the frictional interference between end portions  22 ,  22 ′ of tube  20  and opposing sides  24 ,  26 . In such an embodiment, no extraneous sealing means would be needed. 
   Enclosure  18  is preferably constructed in the general shape of a hexahedron (a three-dimensional, regular polyhedron figure formed by six plane surfaces). Although in order to achieve optimum noise reduction performance for a given application the dimensions of these six surfaces will vary, enclosure  18  was constructed having a Height (H) of 230 millimeters, a Width (W) of 150 millimeters, and a Length (L) of 265 millimeters. Porous tube  20  is comprised of porous, undulated tube material including a series of slotted openings  32  through  42 . This aspect of the present invention will be fully described in conjunction with FIG.  4 . Slots  32  through  42 , are preferably 60 millimeters long  44  and spaced no closer than 20 millimeters  46  to each other. Slots  32  through  42  are preferably five millimeters wide  48 . The nominal Diameter (D) of slotted tube  22  is generally 90 millimeters. 
   Now referring to  FIGS. 2 and 3 , preferably porous tube  20  is oriented within enclosure  18  as shown in FIG.  3 . Most notably, this orientation is not centered within enclosure  18 , but rather porous tube  20  is offset from center, 20 millimeters in the Height (H) direction and is also offset 10 millimeters in the Width (W) direction. This offset both in the Height direction and the Width direction is most easily seen in  FIG. 3  wherein the top of slotted tube  20  is 50 millimeters from the top of enclosure  18  wherein the bottom most portion of slotted tube  20  is 90 millimeters from the bottom of enclosure  18 . Likewise, the offset in the Width position is easily detected from  FIG. 3  wherein the right most portion of slotted tube  20  is 40 millimeters from the right most portion of enclosure  18  as compared to the left most portion of slotted tube  20  which is only 20 millimeters from the left most portion of enclosure  18 . Also, an important aspect of the present invention is the orientation of slots  32  through  42 . The orientation of these slots is clearly shown in FIG.  2  and  FIG. 3  with respect to the sides of the enclosure. Specifically, in order to achieve optimum noise reduction from the intake combustion resonator  10 , slots  32  through  42  should intersect a plane that is generally parallel to the sides of enclosure  18  that form the Height dimension of enclosure  18 . 
   Now referring to  FIGS. 2 ,  3  and  4 , porous tube  20  is preferably constructed from polyester or polyester fibers. Tube  20  is preferably formed using injection molding techniques where the undulating side walls can be easily formed. Other materials such as sintered metal, fiberglass, reinforced resin can be used to fabricate slotted tube  20 . One such source of porous tube  20  is Westaflex Brasil. Westaflex sells porous tube material under the trade name of Sonoflex. Sonoflex is distributed in the USA by West Akron North America, Ltd., 571 Kennedy Road, Akron, Ohio 44305. As best shown in  FIG. 4 , porous tube  20  includes end portions  22  and  22 ′. End portions  22 ,  22 ′ can be integrally formed with porous tube  20  or, in the alternative, they can be formed in a separate process from that used to form porous tube  20  and then, at a later time, joined to porous tube  20  by way of adhesives, welding, or any other method compatible with the materials used to fabricate porous tube  20  and end portions  22 ,  22 ′. End portion  22 ,  22 ′ can be fabricated from the same porous material used to fabricate tube  20 , or in the alternative, any non-porous material may be used such as plastic metal, fiberglass, or the like. 
   Porous tube  20  is preferably constructed with undulating side walls for improved noise abatement properties; however, some level of noise abatement is still achieved if porous sleeve tube  20  is not undulated. Porous tube  20  must be fixed to enclosure  18  such that the orientation of slots  32  through  42  do not change relative to the walls of enclosure  18 . Preferably, tube slots are arranged in pairs (i.e. [ 32 ,  38 ]; [ 34 ,  38 ]; [ 36 ,  42 ]), wherein at least one slot in each pair of slots lies along a common line generally parallel to a center line  19  of said tube. 
   When air flows  50 ,  52  through intake combustion resonator  10 , enclosure volume chamber  54  in combination with tube  20  significantly attenuates any objectionable noise created by the pulsating air flow (typically caused by the engine valve train opening and closing). When the resonator components of the present invention are properly sized and oriented (based on the engine application), the system acts as an air spring mass system to effectively cancel objectionable noise. 
   Now referring to  FIG. 5 , three noise reduction systems were tested and the results are depicted in FIG.  5 . The first system is the system of the present invention. The second system (slot resonator) is a system constructed essentially like the intake combustion resonator of the present invention except that only a non-porous slotted tube was used. The third system tested (porosity duct system) is a system which included an enclosure wherein a porous, non-slotted sleeve was used inside of the enclosure to join intake opening  11  to outlet opening  13 . As is seen from  FIG. 5 , the transmission loss for the system of the present invention is improved over both of the other noise reduction systems especially in the 700 to 2000 Hertz range. 
   The foregoing detailed description of the invention shows that the specific embodiments of the present invention set forth herein are suited to fulfill the objects of the invention. It is recognized that those skilled in the art may make various modifications or additions to the preferred embodiments to illustrate the present invention, without departing from the spirit of the present invention. Accordingly, it is to be understood that the protection sought to be afforded hereby should be deemed to extend to the subject matter defined in the impending claims, including all equivalents thereof. 
   REFERENCE NUMERALS 
   
       
         10  Intake combustion resonator 
         11  intake opening 
         12  intake opening 
         13  outlet opening 
         14  throttle body 
         16  internal combustion engine 
         18  enclosure 
         20  porous tube 
         21  central opening 
         22 ,  22 ′ end portions of tube  20   
         24  opposing sides of  18   
         26  opposing sides of  18   
         28  sealed 
         30  resonator tube assembly 
         32  slotted openings in  20  (porous sleeve) 
         32 ′ slotted openings in  22  (slotted tube) 
         34  slotted openings in  20  (porous sleeve) 
         34 ′ slotted openings in  22  (slotted tube) 
         36  slotted openings in  20  (porous sleeve) 
         36 ′ slotted openings in  22  (slotted tube) 
         38  slotted openings in  20  (porous sleeve) 
         38 ′ slotted openings in  22  (slotted tube) 
         40  slotted openings in  20  (porous sleeve) 
         40 ′ slotted openings in  22  (slotted tube) 
         42  slotted openings in  20  (porous sleeve) 
         42 ′ slotted openings in  22  (slotted tube) 
         44  length of slots 
         46  slot spacing 
         48  Width of slots 
         50  air flow 
         52  air flow 
         54  enclosure volume chamber