Helmholtz Resonator
12-11-2013, 03:45 PM
#1
Helmholtz Resonator
I realize this has probably been discussed before but found this explanation interesting.
Design and Construction
The resonator itself couldn't be simpler in design; it's basically just an expansion chamber or wide spot in the otherwise-smooth intake pipe. It may or may not contain some kind of baffle or plate, depending upon the design and the intent of the designers. Resonators come in two types: In-line resonators are open chambers that sit in the intake tube, while side-branch resonators are chambers that sit next to the tube and are connected to it via a small duct or channel.
The Common Misconception
Most hot-rodders and car enthusiasts think of intake resonators as simple mufflers in the intake tube, devices designed to siphon all the awesomeness out of a car's sound track to appease soccer moms and senior citizens. That makes it a prime candidate for the "chuck-it" school of auto modification. After all, it's basically just a plastic tumor growing off of a tube that should by definition be as smooth and blemish free as possible. While sound control is indeed part of the resonator's job, the sound control itself is really more of a side effect of its primary purpose.
Pressure Wave Harmonics
Air flowing into your cylinder head's intake port doesn't move in a straight line while the valve is open, then politely stop in its tracks to await another valve opening. When the valve closes, the moving column of air slams into it, then compresses and bounces back like a spring. This pressure wave travels backward at the speed of sound until the intake runner opens up or it hits something, and then it bounces back toward the cylinder. This is the "first harmonic." The pressure wave actually bounces back and forth two or three more times before the intake valve opens again.
Intake Tube Pulses
The resonator in your intake is technically known as a Helmholz resonator, an acoustic device used to control pressure wave harmonics. Air bouncing back out of your engine and into the intake tube doesn't do it in a single pulse the way it would in a single intake runner; the multiple pistons put out pressure waves at their own intervals, and some of those are going to try to bounce back in while others are going out. The result is a "clog" or high pressure area in your intake tube that ultimately limits airflow through almost the entire rpm spectrum.
The Resonator
Adding an expansion chamber to the intake tube forces air coming back out of the engine to slow down to fill the cavity, thus expending a great deal of its energy and slowing the pressure wave reversion. This slowdown allows fresh air to flow toward the engine without fighting pressure reversion waves the entire way, thus aiding in cylinder filling. Since these pressure waves are essentially sound, giving them a place to expend their energy before exiting the air filter box ends up dampening the intake noise and quieting the engine. Thus, the resonator helps to make the engine paradoxically quieter and more powerful.
So if the common misconception were true then all aftermarket performance air intakes would include a Helmholtz resonator. The key phrase here is that the pressure waves are essentially sound.
So since I want more sound I am switching to the LS7 air intake from my stock LS3 air intake. I don't believe sound waves have mass therefore they don't affect the air velocity in the intake.
Design and Construction
The resonator itself couldn't be simpler in design; it's basically just an expansion chamber or wide spot in the otherwise-smooth intake pipe. It may or may not contain some kind of baffle or plate, depending upon the design and the intent of the designers. Resonators come in two types: In-line resonators are open chambers that sit in the intake tube, while side-branch resonators are chambers that sit next to the tube and are connected to it via a small duct or channel.
The Common Misconception
Most hot-rodders and car enthusiasts think of intake resonators as simple mufflers in the intake tube, devices designed to siphon all the awesomeness out of a car's sound track to appease soccer moms and senior citizens. That makes it a prime candidate for the "chuck-it" school of auto modification. After all, it's basically just a plastic tumor growing off of a tube that should by definition be as smooth and blemish free as possible. While sound control is indeed part of the resonator's job, the sound control itself is really more of a side effect of its primary purpose.
Pressure Wave Harmonics
Air flowing into your cylinder head's intake port doesn't move in a straight line while the valve is open, then politely stop in its tracks to await another valve opening. When the valve closes, the moving column of air slams into it, then compresses and bounces back like a spring. This pressure wave travels backward at the speed of sound until the intake runner opens up or it hits something, and then it bounces back toward the cylinder. This is the "first harmonic." The pressure wave actually bounces back and forth two or three more times before the intake valve opens again.
Intake Tube Pulses
The resonator in your intake is technically known as a Helmholz resonator, an acoustic device used to control pressure wave harmonics. Air bouncing back out of your engine and into the intake tube doesn't do it in a single pulse the way it would in a single intake runner; the multiple pistons put out pressure waves at their own intervals, and some of those are going to try to bounce back in while others are going out. The result is a "clog" or high pressure area in your intake tube that ultimately limits airflow through almost the entire rpm spectrum.
The Resonator
Adding an expansion chamber to the intake tube forces air coming back out of the engine to slow down to fill the cavity, thus expending a great deal of its energy and slowing the pressure wave reversion. This slowdown allows fresh air to flow toward the engine without fighting pressure reversion waves the entire way, thus aiding in cylinder filling. Since these pressure waves are essentially sound, giving them a place to expend their energy before exiting the air filter box ends up dampening the intake noise and quieting the engine. Thus, the resonator helps to make the engine paradoxically quieter and more powerful.
So if the common misconception were true then all aftermarket performance air intakes would include a Helmholtz resonator. The key phrase here is that the pressure waves are essentially sound.
So since I want more sound I am switching to the LS7 air intake from my stock LS3 air intake. I don't believe sound waves have mass therefore they don't affect the air velocity in the intake.
12-11-2013, 04:23 PM
#2
Racer
Thanks for the post. This is the best explanation I've read so far of the resonator. I don't like how it blocks the serpentine belt, water pump etc. for inspection. But I'm keeping mine. The way I read it, those pulses traveling at the speed of sound is the air column, and air does have mass. So the LS7 doesn't have it...do you think the LS7 is without fault? Good luck, and thanks again.
12-11-2013, 04:29 PM
#3
Burning Brakes
12-11-2013, 04:35 PM
#4
Yea I know, it's complicated. Sound travels at the speed of sound. I don't think the air in your intake does. Think hurricane with 300mph winds, still not the speed of sound and I agree air has mass or hurricanes and tornadoes wouldn't be so devastating. If the air intake if the LS7 and LS3 are identical except for the resonator then I think GM deleted it on the LS7 because they thought people would want to hear more intake sound on the more powerful motor. A marketing tactic and I want more intake sound to go with the NPP so I am switching solely for that reason.
Thank you for the clarification on the LS9 filter element fitment in the LS3-LS7 airbox. I'm sure the supercharged motor requires more air hence the less restrictive filter.
Thank you for the clarification on the LS9 filter element fitment in the LS3-LS7 airbox. I'm sure the supercharged motor requires more air hence the less restrictive filter.
12-11-2013, 04:57 PM
#5
I presume this is your statement and not a quote from the technical article. I suspect that very few aftermarket companies have the financial/technical resources to do a full analysis of the pulse wave phenomenon for every application they manufacture. The ones that do may use a different design that takes into account the volume of the OEM intake, which is easy to measure after the fact….
This is the silliest thing I've ever read. What the heck do you think the MAF sensor does in the intake. Pretty sure the initials stand for Mass Air Flow. Sounds waves ARE essentially a compressed mass of air, which according to the latest physics theory--say from around the mid-1600s--does indeed have mass. I don't have a problem with you saying you'll gladly sacrifice a few HP for more sound….people do it all the time with exhaust mods believing that the least back pressure--and therefore the most noise--equals the greatest HP. But let's not try to rewrite theoretical physics laws.
This is the silliest thing I've ever read. What the heck do you think the MAF sensor does in the intake. Pretty sure the initials stand for Mass Air Flow. Sounds waves ARE essentially a compressed mass of air, which according to the latest physics theory--say from around the mid-1600s--does indeed have mass. I don't have a problem with you saying you'll gladly sacrifice a few HP for more sound….people do it all the time with exhaust mods believing that the least back pressure--and therefore the most noise--equals the greatest HP. But let's not try to rewrite theoretical physics laws.
Feel free to draw your own conclusions and I appreciate your thoughts
If it weren't for us sensory beings, sound might might not be a "thing" at all. Sound as we know it is an interpretation by our nervous system via our sensory organs (well, our ears) of what are essentially vibrations in the air. It has wave-like properties similar to actual things such as light/electromagnetic radiation. But really, sound isn't a thing onto itself outside of what we make of it in our minds, so the question of mass doesn't come into play. Incidentally, the speed of sound is simply how fast vibrations are able to travel through a medium, such as air.
12-11-2013, 06:55 PM
#6
Sound pressure waves can effect many things. Howitzers, with someone close by, can exceed the pressure tolerance of the ear drums, easily blasting them 'out'.
The idea of resonance interference is interesting. Tesla had an invention which was purported to be able to send vibration/resonance waves to jellify a persons brain, or destroy a building by duplicating the buildings specific resonance. Whether that was actual nor not, ask the FBI who confiscated his files when he died.
Hey, I think I feel a little jellification.. right now.
Last edited by J Christensen; 12-11-2013 at 07:02 PM.
12-11-2013, 07:50 PM
#7
Burning Brakes
Senecagreen: Well, to your point, I agree that sound isn't a "thing" but rather an interpreted response of our ears receiving a wave of compressed air and sending a nerve stimuli along the auditory canal to the brain, which then translates the nerve impulse into a known "sound", i.e., music, Vette exhaust, explosion. But whether that pressure wave is from music generated by a stereo speaker or a sonic pressure wave from a closed intake valve bell traveling backward up the intake tract, it most certainly is real and has mass.
I also agree that a little intake honk makes a great sound when you put your foot to the floor!!!
I also agree that a little intake honk makes a great sound when you put your foot to the floor!!!
Last edited by icntdrv55; 12-11-2013 at 07:55 PM.
12-11-2013, 09:02 PM
#10
Hahaha that's funny! I will see if I can get an explanation from GM technical help about why it was added to the C6 LS3 and deleted from the LS7 air intake. I would like to know what their reasoning was since they spend a lot of money on R&D and they are the ones making those decisions.
12-12-2013, 04:38 AM
#12
12-12-2013, 04:46 AM
#13
When you read the above article and get to the helmholtz theory I found out that the helmsholtz resonator is most effective on a single plenum feeding no more than 4 cylinders. To be effective on a single plenum v8 it needs a 180 degree crankshaft and to be even firing which the way I understand it our motors are not.
So the above posters were correct that it aids volumetric efficiency but that is only in certain applications. For our motors the article states that you can realize a small gain at low rpm's but at the cost of high rpm power.
So I think for our motors it basically is used as a acoustic resonator to dampen I take sound and by switching to the LS7 air intake I will neither lose power or gain power I will only get more of a intake honk when I step on it.
Thanks to everyone who motivated me to research this and eventually find the above link that is very informative about all that goes I to creating the right combination of components for power and how they all work together.
So the above posters were correct that it aids volumetric efficiency but that is only in certain applications. For our motors the article states that you can realize a small gain at low rpm's but at the cost of high rpm power.
So I think for our motors it basically is used as a acoustic resonator to dampen I take sound and by switching to the LS7 air intake I will neither lose power or gain power I will only get more of a intake honk when I step on it.
Thanks to everyone who motivated me to research this and eventually find the above link that is very informative about all that goes I to creating the right combination of components for power and how they all work together.
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Ahrmike (04-01-2018)
12-12-2013, 09:15 AM
#15
Race Director
Well I am all about lower power gains so I'll keep it as it is.
High rpms do nothing for me.
Too many years of running 1800-2000- ftlbs tq with 400-500 hp.
High rpms do nothing for me.
Too many years of running 1800-2000- ftlbs tq with 400-500 hp.
12-12-2013, 02:41 PM
#17
The only other purpose it is used for is as a acoustic resonator to cancel out certain sounds and dampen the intake noise. If we had a dual plenum intake then it would be treating our motor as two seperate banks of four cylinders and then it could be designed to aid volumetric efficiency . The article said it is very effective on a dual plenum 6 cylinder where a single plenum feeds 3 cylinders.
It was a very interesting and informative article. We can be thankful that GM does all the hard work to make our motor package a complete design where the size of the components are all matched to each other including a tuned exhaust. I wish I had the modeling software they use that does all the calculations on port size, valve size, camshaft lift and duration, etc
Very interesting stuff
12-12-2013, 03:41 PM
#18
It is possible to see small gains at low rpm with using one plenum for 8 cylinders, but this will usually lead to a reduction in top-end power. There are 3 tunable aspects of the Helmholtz resonator, the plenum volume, intake ram pipe, and intake ram pipe diameter.
V8's with one large plenum feeding all 8 cylinders does not work all that well as far as the Helmholtz resonator goes, but if this is the case, plenum volume should be about 40-50% of total cylinder displacement.
The Helmholtz resonator theory does work well, however, it is limited to how many cylinders can operate off a single plenum. To be effective, no more than 4 cylinders should be used in a single plenum. This set up is very effective on 6 cylinder engine with two plenums, each plenum feeding 3 cylinders. To make matters worse, the cylinders must be even firing, so simply dividing banks of a V6 or V8 will not work unless the banks each fire evenly. For a V8, the best solution is to use a 180 degree crankshaft to even out the firing order of each bank. Then the Helmholtz resonator can be applied as if it were a pair of 4 cylinders.
The above is straight from the article so the conclusion I draw is that it is used for some other purpose in our application and the other use for it is for acoustics.
Less intake noise.
V8's with one large plenum feeding all 8 cylinders does not work all that well as far as the Helmholtz resonator goes, but if this is the case, plenum volume should be about 40-50% of total cylinder displacement.
The Helmholtz resonator theory does work well, however, it is limited to how many cylinders can operate off a single plenum. To be effective, no more than 4 cylinders should be used in a single plenum. This set up is very effective on 6 cylinder engine with two plenums, each plenum feeding 3 cylinders. To make matters worse, the cylinders must be even firing, so simply dividing banks of a V6 or V8 will not work unless the banks each fire evenly. For a V8, the best solution is to use a 180 degree crankshaft to even out the firing order of each bank. Then the Helmholtz resonator can be applied as if it were a pair of 4 cylinders.
The above is straight from the article so the conclusion I draw is that it is used for some other purpose in our application and the other use for it is for acoustics.
Less intake noise.
12-12-2013, 03:53 PM
#19
here is the patent number for using the helmsholtz resonator to reduce intake noise.
INTAKE NOISE MUFFLING DEVICE AND MUFFLING METHOD
JP2008223745
I really enjoyed researching this and thanks to all for the debate. I don't like making changes without knowing the theory behind what I'm doing and now have a greater appreciation for what's involved in component choice.
GM has done a great job in the horsepower war with the other manufacturers...
INTAKE NOISE MUFFLING DEVICE AND MUFFLING METHOD
JP2008223745
I really enjoyed researching this and thanks to all for the debate. I don't like making changes without knowing the theory behind what I'm doing and now have a greater appreciation for what's involved in component choice.
GM has done a great job in the horsepower war with the other manufacturers...
12-12-2013, 04:13 PM
#20
This is the description from GM Global Technology patent number US7694660 B2 dated March 2008 for said device. This is what I think they are using this device for on our engines.
Description
TECHNICAL FIELD
The present invention relates to air induction housings used in the automotive arts for air intake and air filtration for supplying intake air to an internal combustion engine. More particularly, the present invention relates to an air induction housing having a perforated wall for simultaneously providing air intake and sound (acoustic) attenuation, and still more particularly, to a sound attenuation chamber having multiply apertured tubes superposed the perforations.
BACKGROUND OF THE INVENTION
Internal combustion engines rely upon an ample source of clean air for proper combustion therewithin of the oxygen in the air mixed with a supplied fuel. In this regard, an air induction housing is provided which is connected with the intake manifold of the engine, wherein the air induction housing has at least one air induction opening for the drawing-in of air, and further has a filter disposed thereinside such that the drawn-in air must pass therethrough and thereby be cleaned prior to exiting the air induction housing on its way to the intake manifold.
Problematically, a consequence of the combustion of the fuel-air mixture within the internal combustion engine is the generation of noise (i.e., unwanted sound). A component of this noise is intake noise which travels through the intake manifold, into the air induction housing, and then radiates out from the at least one air induction opening. The intake noise varies in amplitude across a wide frequency spectrum dependent upon the operational characteristics of the internal combustion engine, and to the extent that it is audible to passengers of the motor vehicle, it is undesirable.
As shown at FIG. 1, a solution to minimize the audibility of intake noise is to equip an air induction housing 10 with an externally disposed resonator 12 connected to the air induction housing by an externally disposed snorkel 14. The air induction housing 10 has upper and lower housing components 16, 18 which are sealed with respect to each other, and are also selectively separable for servicing a filter media (not shown) which is disposed thereinside. An induction duct 20 is connected to the induction housing and defines an air induction opening 22 for providing a source of intake air to the air induction housing at one side of the filtration media, as for example by being interfaced with the lower housing component 18. An intake manifold duct 24 is adapted for connecting with the intake manifold of the internal combustion engine, and is disposed so as to direct the intake air at the other side of the filtration media out of the air induction housing 10, as for example via the upper housing component 16.
One end of the snorkel 14 is connected to the induction duct 20 adjacent the air intake opening 22. The other end of the snorkel 14 is connected to the resonator 12, which is essentially an enclosed chamber. Each end of the snorkel 14 is open so that intake noise may travel between the induction duct 20 and the resonator 12. The resonator 12 is shaped and the snorkel 14 configured (as for example as two snorkel tubes 14 a, 14 b) such that the intake noise passing through the induction duct toward the air intake opening in part passes into the resonator and then back into the induction duct so as to attenuate the intake noise by frequency interference such that the audibility of the intake noise exiting the air intake opening is minimized.
While the prior art solution to provide attenuation of intake noise does work, it does so by requiring the inclusion of an externally disposed snorkel and resonator combination which adds expense, installation complexity and packaging volume accommodation.
Accordingly, what is needed is to somehow provide attenuation of intake noise as an inherent feature of the air induction housing so as to thereby minimize expense, complexity and packaging volume.
SUMMARY OF THE INVENTION
The present invention utilizes an air induction housing having a perforated wall which provides intake noise attenuation, as is generally described in U.S. patent application Ser. No. 11/681,286, filed on Mar. 2, 2007 to Julie A. Koss and assigned to the assignee of the present invention, the entire disclosure of which patent application is hereby herein incorporated by reference, and further utilizes a sound attenuation chamber interfaced with the perforated wall which provides a second modality of intake noise attenuation, wherein multiply apertured tubes thereof are superposed the wall perforations so that, attendant to the noise attenuation, ample air entry into the air induction housing is provided.
The air induction housing having a perforated sound attenuation wall and interfaced sound attenuation chamber according to the present invention includes an air induction housing having an internally disposed filtration media, and is preferably characterized by mutually selectively sealable and separable housing components; an intake manifold duct interfaced therewith adapted for connection to the intake manifold of an internal combustion engine; a perforated sound attenuation wall connected with the air induction housing and characterized by a plurality of perforations formed therein; and a sound attenuation chamber including a plurality of tubes, each tube superposed a respective perforation of the perforated wall, wherein the tubes have a plurality of apertures in the sidewalls thereof which communicate with an interior space of the sound attenuation chamber. An inner wall of the sound attenuation chamber may, itself, serve as the perforated sound attenuation wall, wherein the tubes' interior openings serve as the perforations. The air induction housing may be of any configuration and is suitably shaped to suit a particular motor vehicle application.
The size, number and arrangement of the perforations and the dimensional aspects of the sound attenuation chamber are selected, per the configuration of the air induction housing and the airflow requirements of the internal combustion engine, such that a multi-faceted synergy is achieved whereby: 1) ample airflow is provided through the perforations and superposed tubes to supply the internal combustion engine with required aspiration over a predetermined range of engine operation, and 2) audibility of intake noise is minimized. The multi-faceted synergy is based upon simultaneous optimization of four facets: 1) providing a plurality of perforations which collectively have an area that accommodates all anticipated airflow (aspiration) requirements of a selected internal combustion engine; 2) minimizing the diameter while simultaneously adjusting the area of the perforations such that the airflow demand of the internal combustion engine involves an airflow speed through each perforation that is below a predetermined threshold at which the perforation airflow noise generated by the flow of the air through the perforations is acceptably inaudible; 3) arranging the perforation distribution in cooperation with configuring of the air induction housing to provide a highest level of intake noise attenuation thereat (i.e., minimal audibility); and 4) further attenuating intake noise at a sound attenuation chamber by a plurality of apertures in the sidewalls of the tubes providing a Helmholtz resonator.
A significant aspect of the present invention is that the intake noise attenuation is accomplished inherently by the air induction housing, itself, obviating need for any external components of any kind (as for example an external snorkel and resonator combination of the prior art).
Accordingly, it is an object of the present invention to provide an air induction housing having a perforated wall which provides a first intake noise attenuation modality and having a sound attenuation chamber interfaced with the perforated wall which provides a second intake noise attenuation modality, wherein multiply apertured tubes thereof are superposed the wall perforations so that, attendant to the noise attenuation, ample air entry into the air induction housing is provided.
This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.
Description
TECHNICAL FIELD
The present invention relates to air induction housings used in the automotive arts for air intake and air filtration for supplying intake air to an internal combustion engine. More particularly, the present invention relates to an air induction housing having a perforated wall for simultaneously providing air intake and sound (acoustic) attenuation, and still more particularly, to a sound attenuation chamber having multiply apertured tubes superposed the perforations.
BACKGROUND OF THE INVENTION
Internal combustion engines rely upon an ample source of clean air for proper combustion therewithin of the oxygen in the air mixed with a supplied fuel. In this regard, an air induction housing is provided which is connected with the intake manifold of the engine, wherein the air induction housing has at least one air induction opening for the drawing-in of air, and further has a filter disposed thereinside such that the drawn-in air must pass therethrough and thereby be cleaned prior to exiting the air induction housing on its way to the intake manifold.
Problematically, a consequence of the combustion of the fuel-air mixture within the internal combustion engine is the generation of noise (i.e., unwanted sound). A component of this noise is intake noise which travels through the intake manifold, into the air induction housing, and then radiates out from the at least one air induction opening. The intake noise varies in amplitude across a wide frequency spectrum dependent upon the operational characteristics of the internal combustion engine, and to the extent that it is audible to passengers of the motor vehicle, it is undesirable.
As shown at FIG. 1, a solution to minimize the audibility of intake noise is to equip an air induction housing 10 with an externally disposed resonator 12 connected to the air induction housing by an externally disposed snorkel 14. The air induction housing 10 has upper and lower housing components 16, 18 which are sealed with respect to each other, and are also selectively separable for servicing a filter media (not shown) which is disposed thereinside. An induction duct 20 is connected to the induction housing and defines an air induction opening 22 for providing a source of intake air to the air induction housing at one side of the filtration media, as for example by being interfaced with the lower housing component 18. An intake manifold duct 24 is adapted for connecting with the intake manifold of the internal combustion engine, and is disposed so as to direct the intake air at the other side of the filtration media out of the air induction housing 10, as for example via the upper housing component 16.
One end of the snorkel 14 is connected to the induction duct 20 adjacent the air intake opening 22. The other end of the snorkel 14 is connected to the resonator 12, which is essentially an enclosed chamber. Each end of the snorkel 14 is open so that intake noise may travel between the induction duct 20 and the resonator 12. The resonator 12 is shaped and the snorkel 14 configured (as for example as two snorkel tubes 14 a, 14 b) such that the intake noise passing through the induction duct toward the air intake opening in part passes into the resonator and then back into the induction duct so as to attenuate the intake noise by frequency interference such that the audibility of the intake noise exiting the air intake opening is minimized.
While the prior art solution to provide attenuation of intake noise does work, it does so by requiring the inclusion of an externally disposed snorkel and resonator combination which adds expense, installation complexity and packaging volume accommodation.
Accordingly, what is needed is to somehow provide attenuation of intake noise as an inherent feature of the air induction housing so as to thereby minimize expense, complexity and packaging volume.
SUMMARY OF THE INVENTION
The present invention utilizes an air induction housing having a perforated wall which provides intake noise attenuation, as is generally described in U.S. patent application Ser. No. 11/681,286, filed on Mar. 2, 2007 to Julie A. Koss and assigned to the assignee of the present invention, the entire disclosure of which patent application is hereby herein incorporated by reference, and further utilizes a sound attenuation chamber interfaced with the perforated wall which provides a second modality of intake noise attenuation, wherein multiply apertured tubes thereof are superposed the wall perforations so that, attendant to the noise attenuation, ample air entry into the air induction housing is provided.
The air induction housing having a perforated sound attenuation wall and interfaced sound attenuation chamber according to the present invention includes an air induction housing having an internally disposed filtration media, and is preferably characterized by mutually selectively sealable and separable housing components; an intake manifold duct interfaced therewith adapted for connection to the intake manifold of an internal combustion engine; a perforated sound attenuation wall connected with the air induction housing and characterized by a plurality of perforations formed therein; and a sound attenuation chamber including a plurality of tubes, each tube superposed a respective perforation of the perforated wall, wherein the tubes have a plurality of apertures in the sidewalls thereof which communicate with an interior space of the sound attenuation chamber. An inner wall of the sound attenuation chamber may, itself, serve as the perforated sound attenuation wall, wherein the tubes' interior openings serve as the perforations. The air induction housing may be of any configuration and is suitably shaped to suit a particular motor vehicle application.
The size, number and arrangement of the perforations and the dimensional aspects of the sound attenuation chamber are selected, per the configuration of the air induction housing and the airflow requirements of the internal combustion engine, such that a multi-faceted synergy is achieved whereby: 1) ample airflow is provided through the perforations and superposed tubes to supply the internal combustion engine with required aspiration over a predetermined range of engine operation, and 2) audibility of intake noise is minimized. The multi-faceted synergy is based upon simultaneous optimization of four facets: 1) providing a plurality of perforations which collectively have an area that accommodates all anticipated airflow (aspiration) requirements of a selected internal combustion engine; 2) minimizing the diameter while simultaneously adjusting the area of the perforations such that the airflow demand of the internal combustion engine involves an airflow speed through each perforation that is below a predetermined threshold at which the perforation airflow noise generated by the flow of the air through the perforations is acceptably inaudible; 3) arranging the perforation distribution in cooperation with configuring of the air induction housing to provide a highest level of intake noise attenuation thereat (i.e., minimal audibility); and 4) further attenuating intake noise at a sound attenuation chamber by a plurality of apertures in the sidewalls of the tubes providing a Helmholtz resonator.
A significant aspect of the present invention is that the intake noise attenuation is accomplished inherently by the air induction housing, itself, obviating need for any external components of any kind (as for example an external snorkel and resonator combination of the prior art).
Accordingly, it is an object of the present invention to provide an air induction housing having a perforated wall which provides a first intake noise attenuation modality and having a sound attenuation chamber interfaced with the perforated wall which provides a second intake noise attenuation modality, wherein multiply apertured tubes thereof are superposed the wall perforations so that, attendant to the noise attenuation, ample air entry into the air induction housing is provided.
This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment.