Quiet intake box for webers R&D, For us wimps Options

['73-914kid]

Well, I'm working on getting the intake noise silenced, and certainly more quiet than it currently is on my car at the moment. Yes, I'm a wimp, and I get BS about it from my dad constantly.

Anyways, I've been throwing around the idea of somehow creating a common plenum style air filter box, similar to that of a 911 engine. Then came my physics class.. We're currently going in depth about standing sound waves, noise cancellation, and acoustics. Amongst this, the topic of Helmholtz resonators came up. Huh, well, that sounds familiar... "used to create destructive interference of standing waves in an internal combustion engine intake system"

The wonderful thing about Helmholtz resonators is that you are not sacrificing ANY air flow through the intake to silence the noise. The box is simply creating a resonating soundwaves with an exactly inverse wave that acts as active noise cancellation. Kinda like this:
(IMG:http://www.914world.com/bbs2/uploads_offsite/library.thinkquest.org-9714-1361412564.1.gif)

For those of you that are not familiar with these on new cars, a Helmholtz resonator is this odd looking box sticking out the side of the intake tube:
(IMG:http://www.914world.com/bbs2/uploads_offsite/images.monstermarketplace.com-9714-1361412564.2.jpg)

The plan right now is to create a common plenum with two pipes leading to a Smooth T in the middle, and then the center pipe having a helmholtz resonator attatched to it. There was also some discussion with my professor that the distance between the carb throats to the resonator might be too great for the sound waves to cancel effectively. The idea of having 2 separate resonators on each connecting pipe is also being considered.

I won't get into the calculations on all of this, for the size geometry, and design of the box, but If I can get this to work, and really silence the intake noise, I will be manufacturing, and selling these systems, for FAR less than the only other common plenum intake system (790 Euros)

This will show the development and design of this system for those that are interested.

[euro911]

(IMG:style_emoticons/default/popcorn[1].gif)

[ruby914]

Cool (IMG:style_emoticons/default/popcorn[1].gif)

[JmuRiz]

Interesting project, I'd just go the easy route and try to find some 912 airboxes...but I'm lazy (IMG:style_emoticons/default/biggrin.gif)

[Black22]

What you just posted is noise cancellation. If you have two sources of the same frequency and flip the polarity of one of the signals 180*, the apparent volume of the sound will decrease. If you combine two identical signals, in phase with one another you will effectively increase the apparent volume. If the signals are the same but do not reach the ears at the same time, you will have phase cancellation. If there are multiple frequencies at the same time, which is more natural than a single frequency, you will have comb filtering.

I think that is right...been 5 years since I've recorded an album of steeped into a studio.

Man I'm getting old, CRS is creeping in.

EDIT: Sorry Ethan, I just scanned your post before replying...you already knew wjhat you were posting about.

[ThePaintedMan]

Well, I'm working on getting the intake noise silenced, and certainly more quiet than it currently is on my car at the moment. Yes, I'm a wimp, and I get BS about it from my dad constantly.

Anyways, I've been throwing around the idea of somehow creating a common plenum style air filter box, similar to that of a 911 engine. Then came my physics class.. We're currently going in depth about standing sound waves, noise cancellation, and acoustics. Amongst this, the topic of Helmholtz resonators came up. Huh, well, that sounds familiar... "used to create destructive interference of standing waves in an internal combustion engine intake system"

The wonderful thing about Helmholtz resonators is that you are not sacrificing ANY air flow through the intake to silence the noise. The box is simply creating a resonating soundwaves with an exactly inverse wave that acts as active noise cancellation. Kinda like this:
(IMG:http://www.914world.com/bbs2/uploads_offsite/library.thinkquest.org-9714-1361412564.1.gif)

For those of you that are not familiar with these on new cars, a Helmholtz resonator is this odd looking box sticking out the side of the intake tube:
(IMG:http://www.914world.com/bbs2/uploads_offsite/images.monstermarketplace.com-9714-1361412564.2.jpg)

The plan right now is to create a common plenum with two pipes leading to a Smooth T in the middle, and then the center pipe having a helmholtz resonator attatched to it. There was also some discussion with my professor that the distance between the carb throats to the resonator might be too great for the sound waves to cancel effectively. The idea of having 2 separate resonators on each connecting pipe is also being considered.

I won't get into the calculations on all of this, for the size geometry, and design of the box, but If I can get this to work, and really silence the intake noise, I will be manufacturing, and selling these systems, for FAR less than the only other common plenum intake system (790 Euros)

This will show the development and design of this system for those that are interested.

Cool Ethan, I'll be watching. I've been working on something similar, albeit without any kid of engineering or noise cancellation in mind. Good luck with it and keep us updated!

[r_towle]

take a look at this.
Very popular in Germany to comply with strict sound pollution regulations.

http://www.csp-shop.com/cgi-bin/cshop2/fro...sort=0&all=

['73-914kid]

Thanks for all the support guys!

That CSP intake box was the one that I was talking about for being so expensive.. it sure is nice looking though. For my case (Broke ass college student) it's way out of my price range. I figure if I can put my head where my wallet would normally be, I might be able to come up with something that works.


Right now, I have a couple sheets of scratched out calculations for size/ etc. My real issue now is going to be measuring the frequency of the sound currently propagating from each weber. My issue is, as Black22 mentioned, is a multitude of frequencies. My plan is to aim for the cancellation of the most apperant frequencies. There's no way to completely cancel the sound, but I'm hoping to significantly decrease it's noticeability.

['73-914kid]

Well, came across some more information. Apperantly you can run a resonating chamber that is basically a one sided tube along the intake runner. The length of the tube should be 1/4 of the wavelength of the standing sound wave. When it reflects off of the closed end, and returns back into the intake plenum, it is exactl 180 degrees out of phase. Im picking up a sound frequency meter from a friend tomorrow, so i'll start taking data on my drive home friday.

[Mikey914]

The science is correct, the problem is the application. Maybe if you had a subwoofer you could create enough sound to cancel. The problem is that you don't have a single consistent tone it has variation in pitch and amplitude. The only way it would work is the wear a noise canceling headset.
We have an ANVS system on the Q400. It works, for the most part. However, it requires maintenance on a regular basis. Microphones go bad due to vibration, the shaker units become un-calibrated, and when there are pitch changes, you can tell the lag, which is irritating. In an aircraft, power changes are minimal, take off, climb, cruse and decent. In a car it will be much more pronounced. Your best bet is to buy a nice cancelling head set, strip out the mic, mounting it about ear level, and find a way to amplify the signal to accommodate an output great enough to have an effect. You'd be out about $300 for a headset+ cost for the speaker set up and other misc items.

http://q400nextgen.com/en/#/q400/technology/anvs/

[euro911]

Just a thought, but wouldn't ducting some intake tubes into the rear wheel wells provide enough distance from the passenger compartment to reduce the level of noise? (IMG:style_emoticons/default/confused24.gif)

Adapting a centralized filter unit then routing to the carbs with something like these?

[dfelz]

Im picking up a sound frequency meter from a friend tomorrow, so i'll start taking data on my drive home friday.

Just make sure that your sampling frequency is at leaset double that of the frequency being measured or else you will have aliasing. Essentially your output frequency will be distorted and "appear" to have a longer period (you will be skipping some of the peaks and valleys.) Haha, this is what we are learning in my theory and design of mechanical measurements class right now! If you ever want any help with the designs or calculations im open MoWeFr and am in the library a lot of that time, and i am always willing to help out if i can. I like projects like this, they are fun and help apply some of the shit we learn in our classes. I am not extremely familiar with taking/analyzing these types of measurements but would love to learn as well!

I dont know what type of frequency meter you will be using, or what kind of option settings it has (if any), but if you want accurate calculations, these are some other things to consider. (IMG:style_emoticons/default/beerchug.gif)

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.ni.com-14538-1361444971.1.JPG)

[r_towle]

look for the parts you may need, or you can make them from fiberglass with foam molds.

using a foam mold, shape it as you like, cover it with fiberglass, then carve out the foam when the shape is dry.

Consider using (for a home built copy of CSP) the turbo hats from CB performance, and a stock beetle airbox from an aircooled beetle.

Rich

[dfelz]

Ya foam molds are always a good cheep (depending on the foam you use) way to get the job done! only problem is there is soooo much foam to clean up after, so have a shop vac near! And you can either do a wet lay-up or if the resources are available, vacum bag it.
Another alternative you can take advantage of is having the mold printed on one of the few 3D printers on campus... the requirements to be able to use it are not very lengthy and it is very inexpensive compared to what it would cost to have it done outside of school. I dont remember what professor you would have to speak to, but if you wanted to go that route later on i am sure i could get a name for you.

[r_towle]

if you go the foam route, use the florest foam, the green stuff.
Its available at michaels or AC moore, or a florist.

It holds up to the resin, its easy to shape, and its easy to remove at the end.

rich

[DBCooper]

Just a thought, but wouldn't ducting some intake tubes into the rear wheel wells provide enough distance from the passenger compartment to reduce the level of noise? (IMG:style_emoticons/default/confused24.gif)

Adapting a centralized filter unit then routing to the carbs with something like these?

It's been done, low-tech and cheap, and more than a few times. Those turbo pressure covers are from CB Performance, and if I recall correctly were connected with silicone turbo hosing to an airbox/filter assy from some Japanese car picked up for a few bucks at a pick-n-pull. It all costs less than $100 and is said to work pretty well. Some enterprising soul should put together kits....

[brant]

what about the goldwing air boxes that Ron invented last month
I think he bought two boxes and significantly improved his noise problem without cancellation, but with simple isolation

all for 100 bucks or something as I recall.

[Elliot Cannon]

(IMG:style_emoticons/default/WTF.gif) Seems like a lot of work to make a beutiful sound go away. (IMG:style_emoticons/default/happy11.gif)

[Randal]

Well, I'm working on getting the intake noise silenced, and certainly more quiet than it currently is on my car at the moment. Yes, I'm a wimp, and I get BS about it from my dad constantly.

Anyways, I've been throwing around the idea of somehow creating a common plenum style air filter box, similar to that of a 911 engine. Then came my physics class.. We're currently going in depth about standing sound waves, noise cancellation, and acoustics. Amongst this, the topic of Helmholtz resonators came up. Huh, well, that sounds familiar... "used to create destructive interference of standing waves in an internal combustion engine intake system"

The wonderful thing about Helmholtz resonators is that you are not sacrificing ANY air flow through the intake to silence the noise. The box is simply creating a resonating soundwaves with an exactly inverse wave that acts as active noise cancellation. Kinda like this:
(IMG:http://www.914world.com/bbs2/uploads_offsite/library.thinkquest.org-9714-1361412564.1.gif)

For those of you that are not familiar with these on new cars, a Helmholtz resonator is this odd looking box sticking out the side of the intake tube:
(IMG:http://www.914world.com/bbs2/uploads_offsite/images.monstermarketplace.com-9714-1361412564.2.jpg)

The plan right now is to create a common plenum with two pipes leading to a Smooth T in the middle, and then the center pipe having a helmholtz resonator attatched to it. There was also some discussion with my professor that the distance between the carb throats to the resonator might be too great for the sound waves to cancel effectively. The idea of having 2 separate resonators on each connecting pipe is also being considered.

I won't get into the calculations on all of this, for the size geometry, and design of the box, but If I can get this to work, and really silence the intake noise, I will be manufacturing, and selling these systems, for FAR less than the only other common plenum intake system (790 Euros)

This will show the development and design of this system for those that are interested.

Maybe I missed it, but is your car a 6 or a 4?

A while ago posted about using a "silencer" on a 6 to make sound at Laguna Seca. Interesting project.

http://www.914world.com/bbs2/index.php?sho...amp;hl=silencer

[KELTY360]

(IMG:style_emoticons/default/WTF.gif) Seems like a lot of work to make a beutiful sound go away. (IMG:style_emoticons/default/happy11.gif)

Hey Elliot, did I ever thank you for those ear plugs you were handing out at WCR08? They worked great! (IMG:style_emoticons/default/shades.gif)