insulating studio walls

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ray and jess

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we are building a recording studio from scratch. I have access to 6 inch foam walls lined on both sides with metal like the type they use in giant coolers or cold storages I wonder if I doublle up the the walls so they would be 15" thick 2six inch panels with 3" spacing in between would it sound proof the studio :confused:
 
Welcome to the board. Soundproof? Against what? 140db jet aircraft? gunfire? Semi trucks? Bulldozers? Bands playing at 110db while mother in law sleeps in adjacent bedroom? Crying babies? Dangerous wifes? :D

First off, I hate to tell you this guys, but there is no such thing as "sound proof". Oh, maybe an underground bombshelter with a 10 ft thick concrete shell. :D But even that wouldn't stop the vibration of a Shuttle take off. if it was 100 feet away. See. Thats why, for studio construction, there is only rated levels of sound transmission LOSS. That means, a product or assembly is tested against a known Sound Pressure Level(spl) in a lab and given a rating for how well it impedes the transmission of sound through the assembly, which is rated as it's TRANSMISSION LOSS. Unless this assembly has a Transmission Loss rating, no one here could possibly tell you how it will perform, especially since you haven't even told us what you are trying to isolate. Thats the usual problem. Its like asking how much gas it takes to drive a thousand miles....but you don't tell us what you are driving and how many miles per gallon it gets or what the terrain is like or how much weight your hauling or....well, you get the picture.

In your case, if I told you yes, it will "soundproof", but didn't tell you it only will only keep the sound of a feather hitting the ground from transmitting through it, you wouldn't be very happy would you? :D Thats the point. If you built an enclosure that will stop the sound from an acoustic guitar from transmitting, it doesn't mean it will keep out the sound of a large truck on a nearby street from getting through, or the sound of drums from getting through. Thats why TL(transmission loss) ratings exist. So designers and architects have a way of knowing how a given assembly design will perform, transmission loss wise.
I will venture to say your proposed design MAY keep low level speech and maybe low level music from transmitting IF these panels were installed using known techniques. But I seriously doubt they will successfully isolate against loud music, especially LOW FREQUENCIES, and impact sounds such as drums. Thats because they have very little MASS. But thats only a guess. Who knows?

Let me give you a little simplified insight into isolation construction. The best bang for the buck construction is a HERMETICALLY SEALED DECOUPLED TWO LEAF, MASS-AIR-MASS assembly with insulation in the airgap. And I DON"T mean foam. Typical residential exterior and interior walls, ceiling/roof and upper floors with a lower floor ceiling leaf are TWO LEAF M-A-M ASSEMBLIES with limited mass and limited airgap. Thats why even low level speech can be heard in adjacent rooms. Usually, the interior mass is simply one layer of drywall. Exterior leaf mass varies. Stucco, T-111 plywood, masonry, OSB, shingles, Board and batten, and other types are typical residential exterior leafs. Ceiling/roof are two leaf assemblies and typically have drywall as an interior leaf, and plywood/OSB and shingles as an exterior leaf, with a large airgap and thin insulation layer in the joist cavities.
Most modern homes have insulation in the stud cavities of exterior walls too.
Filling the airgap with insulation improves the TL of a typical two leaf assembly and dampens the panels which also helps with resonance.

Adding mass, such as multiple layers of drywall, increasing the airgap as far as possible, sealing the airgap EVERYWHERE, and DECOUPLING the two leafs are ways to improve an assemblies transmission loss. Usually by using Resiliant Channel on one leaf, or staggered studs, double walls, or even a floated room. However, there are a thousand caveats here. Sound propagates two ways. Via the air and structural transmission. Doors/jambs, windows/jambs, thresholds, latchsets, HVAC ducting, electrical outlets and switchboxes, fireplaces, pipes, as well as the leafs themself, are all sources of air leaks, as leaf penetrations and small holes will allow sound to propagate. Structural transmission can occur via wood floor framing, direct structural coupling of one leaf to the other by ANYTHING rigid, such as HVAC rigid ducting, electrical conduits, pipes, framing and other mechanical connections. Hence, DECOUPLED assemblies. Usually via resiliant isolators, such as neoprene/EDPM pucks or fiberglass isolators, springs, flexible ducts and conduits and a few other types of products.

Needless to say, High SPL isolation construction is demanding, fairly expensive, and requires a thorough understanding of the principles involved. The best advice I can give you is to READ all you can about this subject. Here is a couple of places to start.

BTW, here is my disclaimer. I'm certainly no expert, and my opinions are exactly that. Opinion, which is subject to clarification, correction and dismissal by those who are. Good luck.
http://www.johnlsayers.com/phpBB2/viewforum.php?f=2&sid=f8f186822f24bb012e5d73978154c7ca
http://forum.studiotips.com/index.php
 
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