US3800910A - Apparatus for directing air flow and sound waves - Google Patents

Abstract

An enclosure, in the form of a mold, attached to the hood or cowling of a vehicle engine, having an air inlet integral with the hood or cowling, combines with the hood to form passages for flow of combustion air to the engine as it passes through the mold. The mold provides cold air to the engine, and in combination with a boot provides control of noise emanating from the engine while being attached to and movable with the hood to provide access to the engine.

Description

United States Patent 1 1 1111 3,800,910 Rose Apr. 2, 1974 [54] APPARATUS FOR DIRECTING AIR FLOW 1,183,670 5/1916 Riker 180/69 R AND SOUND WAVES 2,952,327 9/1960 Farr 180/69 R 2,701,024 2/1955 Thomas 181/33 K [75] Inventor: Jack H. Rose, Livonia, Mich.

[73] Assignee'. Massey-Ferguson 1nc., Detroit, Primary Examiner-Stephen .1. Tomsky Mich. Assistant Examiner-Vit W. Miska [22] Filed:g 2, 1972 Attorney, Agent, or Firm-Thomas P. Lewandowski [21] Appl. No.. 277,462 ABSTRACT 52 US. Cl. 181/35 A, 181/35 R, 181/40, enclosureai of a mid, attached 181/33 E 181/49 181/69 R hood or'cowlmg of a vehicle engine, having an air [5],] In. CL F01 1/00,Foln 5/00, b /00 inlet integral w1th the hood or cowlmg, combmes with 581 Field 01 Search 181/33K 40 35 A the Passages for 0f combusion Isl/35 R 6 6 69 to the engine as it passes through the mold. The mold provides cold air to the engine, and in combination [56] References Cited with a boot provides control of noise emanating from UNITED STATES PATENTS the engine while being attached to and movable with the hood to provide access to the engine. 3,249,172 5/1966 De Lorcan /69 R 2,881,860 4/1959 9 Claims, 5 Drawing Figures Ternes 180/69 "ATENTED APR, 2 I974 SHEET 3 [IF 3 APPARATUS FOR DIRECTING AIR FLOW AND SOUND WAVES It has been a recognized problem in vehicles driven by engines that proper tuning of the engine will be aggravated by hot air being supplied to the engine, particularly in two-cycle engines, for example, those used on snowmobiles. One reason for the above problem in snowmobiles has been the location of the carburetor under the cowling or hood. The location under the hood often arises so as to remove the carburetor from the immediate vicinity of the driver. The entrapped air between the cowling and the engine is heated by the engine before it can enter the engine as combustion air.

One consideration in location of the carburetor arises from its noise level and the transmission of this noise to the driver as well as the surrounding environment in light of recent government regulations on allowable noise levels.

One approach to solving the above problems has been to enclose the opening to a carburetor located beneath the cowling with a type of silencer mounted on the carburetor and in turn directed to an opening in the vehicle body from which fresh air could be drawn. Since the silencer was attached to the carburetor, it could not also be attached to the cowling to obtain an opening to receive fresh air if the cowling was to be removable or movable relative to the engine for servicing the engine. Thus, another problem arose, in crossing over the engine to openings in the vehicle the configuration of the silencer was such as to cover the engine making the engine inaccessible, even with the cowling raised or removed, unless the silencer was dismantled.

Another problem with attempting to silence the operation of vehicle engines is the complexity of the device or apparatus used. The complexity is such as to require the device or apparatus to be fabricated, at least to a partial extent, for all the prior art devices or apparatus.

Contributing to the complexity of the above devices are devious air flow passages incorporated therein as a means of filtration to control noise level. Providing passages which require the flow of air to change direction suppresses the alternating flow of air, which is the source of sound waves, without substantially impeding the steady flow of air needed to operate the engine.

In general, sound results from sound waves transmitted through the air. The waves have a frequency, normally expressed in cycles per second and are generated by vibrations of an object in contact with the air generally referred to as sound radiation. Sound intensity is measured in decibels and is inversely proportional to the area of propagation. Thus, the greater the area into which the sound radiates the lower the intensity, making chambers such as plenums useful for reducing the intensity of a sound. The loudness ofa sound is determined by comparing to a loudness level, normally measured in phons which is a sound of given intensity at a given frequency.

Control of sound, or more particularly noise, can be accomplished by isolation and transmission isolation methods in addition to filtration methods. Isolation is the prevention of one portion of a machine or structure from setting another portion into vibration which may be a more effective radiator of sound. For example, the

vibrations of an engine should be prevented from setting the cowling of the vehicle in which the engine is mounted into vibration with the engine. Similarly, if air with alternating flow can be confined, for instance in a chamber, then the vibrations or sound Waves are restricted in their ability to transmit sound.

Transmission isolation is an additional aid to control more particularly oriented to transmission through so]- ids as opposed to fluids whereby elastic discontinuities may be introduced into structures in which sound transmission is a function of the density and sound velocity for the material involved. Thus, in our example of the engine and the cowling if a direct connection were made between the two it would allow transmission along and through the connector. Introduction of an elastic discontinuity in the connector itself or in addition to the connector would decrease the effectiveness of the connector as a sound transmitter.

The last problem, but by far not the least, is the increased cost of the additional materials to solve the above problems. As mentioned previously, the prior art devices are complex and require considerable materials which must be at least partially fabricated all of which substantially increase cost.

The present apparatus for directing combustion air going to and sound waves emanating from an engine solves the above problems. The apparatus includes an enclosure attached to an air inlet integral to the covering over the engine and a boot for interconnecting the enclosure to the engine. Mounting the enclosure on the covering allows it to move with the covering to provide free access to the engine While the engine is provided cold air from the air inlet. By incorporating the inlet in the covering the enclosure is simplified. Use of the covering to form air passages between the covering and enclosure eliminates the requirement for fabrication. The boot alleviates the problems of noise transmission to the covering and lowers the requirement for dimensional tolerance between the engine and the enclosure.

The elimination of fabrication on the enclosure combined with a reduction in material on the present apparatus because of its simpler design in extending to the covering rather than the vehicle body, results in a substantial cost savings over the prior art devices.

The present invention relates to apparatus for directing combustion air going to an engine and sound waves emanating from the engine and more particularly to apparatus incorporated with and attached to a covering over the engine. An air inlet for admitting cold air located in a cavity in the covering connects to an opening in one end of the enclosure, and the enclosure extends toward the engine where another opening is provided in the enclosure. Means for fluidly sealing the other opening to the engine are also provided.

In one embodiment, an open faced mold, having an opening in the end opposite the open face portion, forms the enclosure. The open face of the mold has a configuration to match with the cavity containing the air inlet to which it is attached, and thereby forming passages of a devious nature for directing combustion air to the engine. The passages filter the sound waves emanating from the engine by redirecting them to muffle the noise. A boot of flexible material provides the means of connecting the mold to the engine and allows the mold to travel with the covering when the covering is moved relative to the engine to provide access thereto. The mold incorporates a plenum and may include directing vanes and ram tubes'to further direct air flow to the engine. The plenum also provides a greater area of propagation for sound waves to help reduce the loudness of noise emanating from the entry to the engine.

FIG. 1 is a fragmentary elevational view of a vehicle incorporating apparatus in accordance with the present invention having portions broken away to reveal greater detail;

FIG. 2 is an enlarged view of a portion of the vehicle illustrated in FIG. 1 better illustrating the apparatus incorporated therein with further portions thereof broken away to reveal further detail;

FIGS. 3-5 are cross-sectional views of the apparatus cowling orhood 20, by a plurality of bolts andnuts 22 and 24 as best illustrated in FIG. 2. As will be subsequently described in greater detail, themold 18 combines with a portion of the hood adjacent it to form passages for directing the flow of cold air entering aninlet 26 to thecarburetor 14. In the embodiment illustrated, theinlet 26 is in the form of a pair of slots 28 (best illustrated in FIG. 4) in an identation in thehood 20. One skilled in the art would be aware of numerous modifications which could be made to the size, shape and orientation of theinlet 26 to suit other engine and covering applications. Modifications to theboot 16 will also be apparent to one skilled in the art. Other means of sealing the enclosure to theengine 12 could be, for example, a flexible hose. Further, the sealing means could be attached to the enclosure as well as theengine 12,.partic ularly in otherembodiments where it may not be as practical to attach it to the engine involved.

The use of themold 18 is particularly advantageous in the snowmobile where theengine 12 and particularly thecarburetor 14 are adjacent the drivers position, indicated generally by thenumeral 30. Themold 18 has the advantage of the ability to decrease the loudness of the noise experienced by the driver. A further advantage in use of themold 18 is to direct cold air to theengine 12. The cold air is preferable over hot air which otherwise would be available beneath thehood 20 of the snowmobile having been subjected to the heat of theengine 12. The difficulty in'tuning theengine 12 when hot air is supplied is reduced when cold air is used to prevent detonation and overheating of theengine 12 under sustained full load performance.

Typically, thehood 20 is raised by pivoting it about the front of the snowmobile to expose theengine 12 for servicing. When thehood 20 is pivoted, themold 18 moves with it and theboot 16 provides a parting line between themold 18 and the carburetor Theboot 16 is preferably made of flexible material with a degree of resilience to permit it to adapt to the shape and position of the mold. Rubber would be a good example of material suitable for theboot 16. The adaptability of theboot 16 to the position of themold 18 results in a substantial lowering of the requirements of dimensional tolerance on the mold l8 andhood 20. Sealing of the air flow through the apparatus is also enhanced by the flexibility of the boot. The requirements of expansion provisions in interconnecting thehood 20 andengine 12 are also lowered. Control of noise emanating from theengine 12 is provided by theboot 16 in the form of transmission isolation. The transmission of the vibrations of theengine 12 to the hood are isolated by the elastic discontinuity of theboot 16 to prevent thehood 20 from becoming a radiator for the noise of theengine 12.

Referring to FIGS. 1 and 2, a raisedportion 32 of thehood 20 has its continuity broken by a surface 34 which is indented at a gradual angle as it approaches theinlet 26. Theinlet 26 is located between the indented surface 34 and the top of the raisedportion 32 in a nearly vertical plane which facilitates the entry of air into theinlet 26. Thesides 36 of the raisedportion 32, one of which can be seen in FIG. 2, drop below the upper portion of themold 18 immediately adjacent themold 18 as illustrated in FIG. 4. Theinlet 26, sides 36 and arib boss 38, on the underside of the raisedportion 32 of thehood 20, form a cavity for receiving themold 18. Protruding at generally a right angle from thehood 20, therib boss 38 is a continuous member extending between thesides 36 of the raisedportion 32 generally paralleling theinlet 26. A plurality of tappedholes 40 are provided in therib boss 38 for receiving thebolts 22. Similarly, a series ofbosses 42 having tappedholes 44 therein are provided beneath the identical surface 34 adjacent theinlet 26. t

Themold 18 has a raisedinner portion 46 which is positioned adjacent the theinlet 26.

Themold 18 has a raisedinner portion 46 which is positioned adjacent the top of the raisedportion 32 when themold 18 is placed within the cavity of theI hood 20. Aseal 48 may be inserted between thehood 20 and themold 18 to militate against the flow of air across the mating line between the raisedinner portion 46 of themold 18 and thehood 20. Preferably, the seal is air imperious and applied to themold 18 with an adhesive. When the raisedinner portion 46 is considered together with a pan shapedportion 50 of themold 18, it will be found that passages for directing air flowing in theinlet 26 are formed between the pan and raisedinner portions 50 and 46 of the mold l8 and the cavity in thehood 20.

Thepan portion 50 of the mold is illustrated in FIG. 2 having a bottom, front andrear walls 52, 54 and 56, respectively, from which front and rear flanges, 58 and 60 respectively, extend outwardly from and generally parallel to thebottom wall 52. Theflanges 58 and 60 provide a seat for the nuts 24 which fasten themold 18 to thehood 20.

Arear passage 62 and a portion of afront passage 64 can be seen in FIG. 2.Side passages 66 can be seen in FIG. 4 as formed by thebottom wall 52,side walls 68, sides 36 and top of the raisedportion 32 of thehood 20 and the raisedinner portion 46 of themold 18. The closeness of theside walls 68 to thesides 36 of thehood 20 effect an air seal between them.

The devious flow path of air flowing through the passages is best illustrated in FIG. 3 by arrows showing the direction of flow which is split upon entering the twoopenings 28 in the inlet 26 (see FIG. 4) and upon contact with the raisedinner portion 46 of themold 18. Thefront passages 64 have cross sections which diverge from the center of the incoming stream to each side of themold 18 to accommodate the accumulation of air across the face of each opening 28 in theinlet 26. The air diverted by the raisedinner portion 46 enters theside passages 66 and is further directed to therear passages 62 which converge at anentry 70 before entering aplenum 72. Theentry 70 is an opening in the raisedinner portion 46 which converges downwardly to direct theflow into the plenum. The angle of convergence may be varied in accordance with the system resistance experienced.

. Expansion of the air, upon entering the plenum decreases the velocity of the air in the plenum resulting in less turbulence in the air leaving a discharge port which is a circular opening 74in the bottom of theplenum 72 in the embodiment illustrated. The opening connects to theboot 16 to direct the air to the carburetor l4 and could be other than circular in shape.

The mold 1 8 is adaptable to receiveair vanes 76 which may be added to further assure a laminar flow of air enters thecarburetor 14 by breaking up any tendency of the air to swirl in leaving theopening 74. An alternative to theair vanes 76 would be a tuning tube, not illustrated, which would be inserted into theopening 74 to form an annulus therebetween. The tuning tube could be accommodated for mounting in themold 18 or on the carubretor l4, and further, air vanes could be added to the annulus formed between the tuning tube and discharge port of themold 18.

It should be noted that the above described passages 62-66 for the flow of air are generally maintained in the cavity of the raisedportion 32 of thehood 20 with at least one side of the passages 62-66 being a portion of thehood 20 which is shielded from the engine heat. Thus, the air in the passages is maintained cool in passing through the passages. Both the cross-sectional area of theopenings 28 in the-inlet 26 and that of the area of passages combining to supply air to thecarburetor 14 should be greater than the entry area ofthecarburetor 14. g

Referring to FIGS. 24 the shape of themold 18 while somewhat intricate is such as to enable it to be cast in one pieceQparticularly because the tops of the passages-62-66 are formed by thehood 20 to enable themold 18 to be formed with an open face as a single piece mold. The raisedinner portion 46 of themold 18 is formed by raising a part of thepan bottom wall 52 around the periphery of theplenum 72 upward to a position adjacent the top of the raisedportion 32 of thehood 20. The portion immediately adjacent thehood 20 is flat forming aridge 78 to accommodate theseal 48. Theridge 78 encompasses the top of the plenum over its entire periphery except for that part where theentry 70 exists. As a result of the above construction, theentry 70 is completely shielded from theinlet 26. Downwardly extending outer andinner partitions 80 and 82 extend over the periphery of the raisedinner portion 46 from theridge 78. The spacing and orientation of the partitions is a function of the desired position of theplenum 72, and the requirements for making a practical andsatisfactory mold 18.

Theouter partition 80 interconnects theridge 78 with theflange 58 at the front of themold 18 in the area adjacent the middle boss 42 (see FIG. 3), and with thebottom wall 52 along the remainder of the front as well as the sides and'rear of the mold l8. Extending down beyond thebottom wall 52 theinner partition 82 forms the sides of theplenum 72. FIG. 2 illustrates a projection in the rear portion of the sides of thepienum 72 to form theextended partition 84 immediately below theentry 70. In FIG. 3, theend partitions 86 interconnecting the inner andouter partitions 82 and extend down below thebottom wall 52 inlegs 88 which interconnect theinner partition 82 with theextended partition 84. The end partitions converge upon each other but do not meet at the bottom of the plenum resulting in theextended partition 84 having a V-shape with a flat bottom which acts as a stiffener to prevent flexing of the rearward portion of theinner partition 82 while providing a larger entry to theplenum 72 and directing the air flow toward the center of theplenum 72. FIG. 5 best illustrates the V-shape of theextended partition 84 which preferably corresponds to the convergence of theentry 70.

FIG. 4 illustrates the shape of the bottom of theplenum 72 which includes aninclined surface 90, and a generally horizontaltransitional surface 92 which together direct the flow of air to theopening 74. Asnout 94 connects theopening 74 totransitional surface 92 and has a rightcylindrical portion 96 and aconical portion 98. Placement of theconical portion 98 at the proper angle to thecylindrical portion 96, as illustrated in FIG. 2, brings thesnout 94 into seating alignment with theboot 16. Seating and sealing are both enhanced by the taper of theconical portion 98 which permits insertion of theopening 74 of thesnout 94 into the opening in theboot 16. Theconical portion 98 also serves to house theair vanes 76 which are rotated 45 out of phase, in FIG. 2, to present them in true profile. Thevanes 76 have basically rectangular faces with ataper 100 on each end to conform them to the shape of theconical portion 98 and achamfer 102 on the corners opposite thetaper 100 to permit clearance between thevanes 76 and thecylindrical portion 96 as at 104.Protrusions 106 may be added to the vanes to aid in securing their position within thesnout 94. Theprotrusions 106 mate withrecesses 108 in theconical portion 98, as best illustrated in FIG. 1. Preferably, the vanes'76 are made of the same material as themold 18 and may be permanently attached by a suitable adhesive. An example of a suitable material for the mold would be ABS-LE cycolac, others could be used.

Noise and noise control is a science complicated by many variables which are often of a nature defying isolation making it difficult to measure a level of noise. As a result, the specific point of improvement or the most effective element in obtaining a quieter application often cannot be stated with certainty. It is possible, however, to point out particular features which are amenable to the basic principles of noise abatement and present in the apparatus described above.

Viewing the devious flow paths for the air traveling in the passages 6266, described above with respect to FIG. 3, it can be seen that the alternating flow or sound waves in the air which attempt to travel back through the passages will be subjected to filtration at each degree turn in the path leading back to theinlet 26. Further, the splitting of the passages 62-66 permits the placement of theentry 70 to the plenum in a manner completely shielding it from'theinlet 26. Themold 18 itself, of course, isolates vibrations of the air by confining the alternating air flow emanating from thecarburetor 14 within themold 18. Further, the intensity of the sound is lowered by the large area of propagation provided by theplenum 72 over which the sound waves may be dispersed before being transmitted out theinlet 26.

It should also be noted that theinlet 26 is positioned to direct any sound emanating therefrom in a direction opposite to that of theoperators station 30, see FIG. 1.

An actual test Comparing the noise with the above apparatus mounted on an engine with that when the apparatus was removed showed a reduction of up to 3 dbA or approximately a 25 percent reduction in noise level.

Thus, even though a direct connection was made between the engine and the hood thereover, the use of the above apparatus reduced the noise level below that of the engine and covering alone.

In addition to the above advantages with respect to directing air flow and sound waves, the above apparatus has the advantage of lower cost over prior art apparatus ofa fabricated nature in that themold 18 does not require fabrication but is molded in a single piece. Further cost reduction comes from direct connection of themold 18 to thehood 20 which is a simplification over the more complex approach of extending to inlets in the side of the vehicle body for instance. At the same time, the simplicity of themold 18 makes it readily adaptable to mounting on thehood 20 for movement with thehood 20 when the hood is raised to part the apparatus at theboot 16 as described above.

It is to be understood that themold 18 is adaptable to other engine and hood configurations while maintaining its characteristics of devious flow paths, shielding of the entry from the inlet, a plenum, snout and the open face combining with the configuration of the hood. The offset ofthesnout 94 in FIG. 4 is an example of this type adaptability to accommodate acentered inlet 26 with an offsetcarburetor 14.

In accordance with the provisions of the patent statutes, the principal and mode of operation of the apparatus have been explained and what is considered to represent its best embodiment has been illustrated and described. It should, however, be understood that the invention may be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.

What is claimed is:

1. In a vehicle having an engine with a covering and an inlet therein, apparatus for directing combustion air going to and sound waves emanating from the engine comprising: a single piece enclosure attached to and movable with the covering having an opening therein; an open face on said enclosure for engagement with the covering, said enclosure including an inner portion within and spaced from the outer periphery of said open face extending toward the covering to form passages for directing the flow of air, and extending away from the covering to form a plenum for receiving said flow of air from said passages and slowing the velocity of incoming air directed to the engine while also dispersing sound waves; and means for sealing by contact the opening of said enclosure to the engine, said open face of said enclosure being connected to the inlet to cause outside air to be directed to the engine and to isolate the sound waves traveling through said enclosure.

2. The apparatus defined in claim 1 wherein said enclosure includes an entry internal of said enclosure for passage of air to the opening of said enclosure, said entry located in said inner portion extending toward the covering to permit shielding said entry from the inlet by said inner portion to reduce the noise level at the inlet originating from said entry.

3. The apparatus defined in claim 1 wherein said enclosure includes a snout containing the opening in said enclosure.

4. The apparatus defined in claim 1 including a seal for sealing a portion of said enclosure to the covering.

5; The apparatus defined in claim 1 wherein said means for sealing includes a boot for selectively sealing the connection of said boot to said enclosure to permit said enclosure to move with the covering.

6. The apparatusdefined in claim 1 wherein said enclosure is adaptable to receive air flow directing vanes located within said opening of said enclosure.

7. The apparatus defined in claim 1 wherein said enclosure is a single piece mold and said sealing means is a boot, said inner portion including a ridge, said ridge encompassing the upper portion of said plenum and being connected thereto by an inner partition, said mold further including an outer partition and a pan shaped portion, said outer partition interconnecting said ridge with said pan, at least a portion of the perimeter of said inner and outer partitions being cut away to form said entry into said plenum above said pan, said outer partition, pan shaped portion and the covering combining to form devious passages for the flow of air from said inlet.

8. The apparatus defined in claim 7 including a snout on said plenum having cylindrical and conical portions, said conical portion adapted to seat within said boot.

9. In apparatus for a vehicle with an engine and a covering therefor, the apparatus directing combustion air going to and sound waves emanating from the engine and being located between the covering having an inlet therein and means for sealing the apparatus to the engine, a single piece mold comprising: an open face on said mold for engagement with the covering; an inner portion within and spaced from the outer periphery of said open face extending toward the covering to form passages for directing the flow of air; a plenum formed by extending said inner portion away from the covering for slowing the velocity of incoming air and dispersing sound waves; and an entry internal of said mold located in said inner portion to shield said entry from the inlet by said inner portion to reduce the noise level at the inlet originating from said entry.

Claims (9)

1. In a vehicle having an engine with a covering and an inlet therein, apparatus for directing combustion air going to and sound waves emanating from the engine comprising: a single piece enclosure attached to and movable with the covering having an opening therein; an open face on said enclosure for engagement with the covering, said enclosure including an inner portion within and spaced from the outer periphery of said open face extending toward the covering to form passages for directing the flow of air, and extending away from the covering to form a plenum for receiving said flow of air from said passages and slowing the velocity of incoming air directed to the engine while also dispersing sound waves; and means for sealing by contact the opening of said enclosure to the engine, said open face of said enclosure being connected to the inlet to cause outside air to be directed to the engine and to isolate the sound waves traveling through said enclosure.

2. The apparatus defined in claim 1 wherein said enclosure includes an entry internal of said enclosure for passage of air to the opening of said enclosure, said entry located in said inner portion extending toward the covering to permit shielding said entry from the inlet by said inner portion to reduce the noise level at the inlet originating from said entry.

3. The apparatus defined in claim 1 wherein said enclosure includes a snout containing the opening in said enclosure.

4. The apparatus defined in claim 1 including a seal for sealing a portion of said enclosure to the covering.

5. The apparatus defined in claim 1 wherein said means for sealing includes a boot for selectively sealing the connection of said boot to said enclosure to permit said enclosure to move with the covering.

6. The apparatus defined in claim 1 wherein said enclosure is adaptable to receive air flow directing vanes located within said opening of said enclosure.

7. The apparatus defined in claim 1 wherein said enclosure is a single piece mold and said sealing means is a boot, said inner portion including a ridge, said ridge encompassing the upper portion of said plenum and being connected thereto by an inner partition, said mold further including an outer partition and a pan shaped portion, said outer partition interconnecting said ridge with said pan, at least a portion of the perimeter of said inner and outer partitions being cut away to form said entry into said plenum above said pan, said outer partition, pan shaped portion and the covering combining to form devious passages for the flow of air from said inlet.

8. The apparatus defined in claim 7 including a snout on said plenum having cylindrical and conical portions, said conical portion adapted to seat within said boot.

9. In apparatus for a vehicle with an engine and a covering therefor, the apparatus directing combustion air going to and sound waves emanating from the engine and being located between the covering having an inlet therein and means for sealing the apparatus to the engine, a single piece mold comprising: an open face on said mold for engagement with the covering; an inner portion within and spaced from the outer periphery of said open face extending toward the covering to form passages for directing the flow of air; a plenum formed by extending said inner portion away from the covering for slowing the velocity of incoming air and dispersing sound waves; and an entry internal of said mold located in said inner portion to shield said entry from the inlet by said inner portion to reduce the noise level at the inlet origiNating from said entry.

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