Home Garage Noise Control

[JoeP]

Does anyone have a tricky way to control sound levels when tuning a track car at home? I have nice neighbors, but this is way too loud for more than a minute or two. If necessary, I plan to build something from scratch.

[saucerman]

I've asked a friend to answer you since he knows a thing or two about this very subject -

Ultimately, it depends on how much attenuation you’re trying to achieve and at what frequency(s). Since we’re talking a garage and a Porsche, I imagine the lovely 80db growl between 50-300 Hz is the main thing that is rattling the neighbors, which of course happens to be the toughest to work with.

Sound travels in two ways, through the air and via vibration through materials. I’m sure you’ve observed that lower frequencies cause more vibration than higher frequencies. In this case, slapping foam on the walls will only attenuate frequencies above 300 Hz (which will not address the real problem). The only solution here is to add mass to stop the transmission via the air and add a layer of isolation so the vibrations do not transfer between surfaces. Putting foam/carpet/egg crates on the wall will have some effect, but it is probably a waste of money. Below are some options, none of which are necessarily cheap, however the cost could be minimized if you have basic carpentry skills, a few friends, a case of beer, and only the offending wall is treated.

1) Add a layer of 5/8” drywall to the existing drywall. (-5db)

2) Build an air pocket using ¾ furring strips in front of the existing drywall 24” on center. Then attach 5/8” drywall to the furring strips (-15db, maybe more). The wide spacing of the furring strips minimizes the points where vibration can pass from wall to wall. Adding a second layer of 5/8” drywall will probably drop it some more, but you’ll need to reduce the spacing to carry the weight. Probably not worth the cost/effort as you’ll only gain an extra 3-5 db.

3) And finally, the correct way to “sound proof” a room (-40db+):
- Frame a 2x4 wall 16” on center spaced 1” from the existing wall (metal studs will transfer less, but wood’s fine too).
- Add R12 insulation between the studs.
- Attach 2 layers of 5/8” drywall to the newly framed wall.

[JoeP]

Thanks for the reply. I guess that my garage rates a solid "B" on soundproofing. I put rigid foam between the studs, a layer of 5/8" wall board, new windows, and triple layer 1.5" thick steel garage doors.

I should have been more clear. Since I cannot run the engine for long inside a closed garage, I was thinking of building some sort of external muffled box or tubes to fit over the exhaust exits to limit the sound to a reasonable level.

[jmr3]

Stick a banana in the tail pipe and you will be fine.

[saucerman]

JMR3 you should have used

anyway....to muffle the sound at the exhaust pipe will probably also restrict airflow and I'm not sure if that is a wise move or even if something like that exists.

[JoeP]

OK. I need to try something. I'll post results if it works --- or catches fire.

[michael lang]

Whenever I am doing something like that in my garage I usually walk next door and say something to the woman a day or two before i plan on doing whatever it is that requires me to run the motor. This gives her a chance to decide if she and her husband want to stay at home or they can leave. So far that approach must be working because they are still inviting the kids over to play in the pool.

[ccm911]

Joe, what about those foam rubber "egg crate" things that they use in radio studios? I'll bet you could glue that up in a morning, and it should hold down the sound. But it will hold odors. So don't fart while working on the car.