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

[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)

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)

Yeah. They do work great. I use them mostly for the road noise. The sweet engine sound still comes through. My wife uses them when she sleeps. I'm not sure why? (IMG:style_emoticons/default/lol-2.gif)

[bam914]

Just use mine.

http://www.914world.com/bbs2/index.php?sho...=148543&hl=

[7TPorsh]

huh? WHAT?

[monkeyboy]

Silly question...

If you tune it for a certain frequency, how will you keep it from amplifying other frequencies?

Remember, the motor operates over a range of frequencies. If you tune it to cancel a certain frequency, you will also get other frequencies that it amplifying.

[dfelz]

Silly question...

If you tune it for a certain frequency, how will you keep it from amplifying other frequencies?

Remember, the motor operates over a range of frequencies. If you tune it to cancel a certain frequency, you will also get other frequencies that it amplifying.

Could you use a low-pass filter to accommodate for that. Anything above XX Hz is filtered out...?

[rgolia]

If you can make one that works at a reasonable cost...I am in. Old ears do not like lots of noise.

[euro911]

Do you have access to a portable spectrum analyzer to do your sound testing?

[euro911]

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.

I picked up a couple of them from ebay sellers ... about $50 or so for both. Unfortunately, they sit pretty tall in the engine bay ... don't want to give up my rain tray. They look like they'd be great for those running without (IMG:style_emoticons/default/idea.gif)

['73-914kid]

For now, my phone has an app for spectrum analysis that gives me a fairly accurate reading for frequency. From that, i can calculate wavelength hopefully.

Right now, im considering whether or not a true noise cancellation setup is really needed.. if i can get something to work as a kit without it, that will be devloped..

[monkeyboy]

Silly question...

If you tune it for a certain frequency, how will you keep it from amplifying other frequencies?

Remember, the motor operates over a range of frequencies. If you tune it to cancel a certain frequency, you will also get other frequencies that it amplifying.

Could you use a low-pass filter to accommodate for that. Anything above XX Hz is filtered out...?

Not sure how you would accomplish that.

Read this... http://library.thinkquest.org/19537/Physics5.html

[michael7810]

Mark. Bring your GW air filters to Rt 66 if you. Want to sell them.
Mike

[euro911]

Hey Mike - I just went back to my ebay history ... they cost $60. including shipping for both of them.






Not sure if I'm gonna make the RT66 this year (yet) (IMG:style_emoticons/default/dry.gif) ... but maybe I could entice a local from here to transport them if you're interested (IMG:style_emoticons/default/confused24.gif)

[FourBlades]

There must be value in the intake resonators even though there are lots of sound frequencies to deal with because most new cars include them.

The big car companies must have this figured out, maybe you can find out what they are doing.

Maybe try cutting one off an intake from a 2 liter/4 cylinder car in a junk yard and graft it into your intake and do some sound level measurements.

John

[VaccaRabite]

Or go back to a stock plenum and add EFI.

or 912 air cleaners. Nearly bolt on.
Or beetle air cleaners.
There have been several threads for folks that have done this. I was looking at doin it a few years back but went for EFI and ditched the carbs. I know most like the noise of screaming IDFs at 4k, but I like to finish a 50 mile drive without a headache.

Do it. Make a kit you WILL sell them.
Zach

[FourBlades]

I built a cheesy intake a year or so ago to see if it would quiet things down and then tried to measure it.

This is the idle measurement with ITG foam filters. The ITG filters are really well made but by far the loudest I tried. For autox, DE, racing they seem like a good way to go.



Here is the intake I built so I could get some measurements. This is just welded up from 18 gauge. The round tube is 3" steel exhaust pipe from the flaps. I eventually wrapped the air boxes in dynamat.



(Air box tops are off in this picture).



Here is the idle measurement with the ugly box:



The RPM numbers on my timing light are not accurate in the picture because of the strobe effect of the old fashion LED digits. The last reading looks like 640 but it could easily be 880 but the camera did not capture the other segments lit.

It seems from my cheap sound meter that it is 6 db quieter. I photographed 6 or 7 measurements each way and these are about the averages.

Driving the car it does not seem that much quieter. The raspy edge you get when the throttles are open is gone, but the engine as a whole just makes a lot of noise. I think having some kind of insulated rain tray that blocks more of the noise from the engine would be more effective in making it quieter. I keep planning to build a thin rain tray and then line it with dynamat. Of course you need enough air opening to keep the engine cool and fed.

One improvement this air box makes is that your idle is smoother and stronger, I think because you have better air velocity at low RPM. I could not measure this effect but it was noticable in improved drivability at low RPM. I am sure the high RPM performance was hurt but I rarely rev past 5000 anyway.

I ended up making a nicer version that I need to take a picture of.

John

[euro911]

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[johnpierre]

i love watching you all crack out on this stuff. i wish i was a little bit more advanced when it comes to these details. that is ok "a long journey starts with one step." haha

[Valy]

Your idea works nice in 2 dimensions. When you go 3d everything goes wrong and here are some simple issues you'll have ro deal with:
1. Your microphone is dirrectional and doesnt have the capacity to detect the sound wave propagation. All you can do is build a canceling wave that will cancel the noise at the mic.
2. Your speakers are dirrectional so if you want to cancel the sound in one place, you don't have much control over the other locations.

[Dave_Darling]

My wife uses them when she sleeps. I'm not sure why?

Mostly for the road noise...

--DD

[euro911]

I understand the inverted sine wave (negative noise) theory/practice to cancel out primary sound waves. MANY years ago we used 'negative noise amplification' technology for video duplication, but not sure why all the electronics are required for an automotive application, unless it's more of an engineering exercise?

Please continue with your study as I'm really interested in seeing the results ... I'm just leaning more towards a mechanical solution for my application.

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