Soundproofing Walls: My Results

James Boyd

Historical re-cap:

I have been concentrating efforts on selling sound isolation jobs. Nothing huge like commercial theaters or schools, I'm not an acoustical consultant. Just residential. I believe them to be potentially much higher in profit than standard drywall jobs where I'm competing with so many others. Also, people who need soundproofing really need it, and are less concerned about cost.

But how to soundproof in a way that wasn't super expensive, wasn't too difficult for an un-technical crew and reasonably fast? I started looking at various soundproofing techniques and asking a lot of questions. Over the last 6 months, I have lurked around several acoustic, recording studio and hometheater forums. I gathered a lot of information.

Whew!

Well, the first job is done and we've been paid in full. Customers are happy as hell and they got me another lead. I wish I started this a year ago.

James

fastg60

what materials are you using? do you have any pics of your jobs?

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Around The House

Remodeling and painting.

James Boyd

Pictures! Argh! I should have taken pictures.

I took the existing wall, blew in cellulose, and added a layer of 5/8" with green glue. Acrewed to the studs as usual. Mudded and taped. Worked like a charm and was relatively inexpensive. Made good profit. In fact, I'm looking to charge more.

James

Frankawitz

James
here's something to think about, I do all repair work and all of our repairs involve water damage, Well when cellulose gets wet it weighs a ton, and Black mold grows real good inside of the stuff , also in the cold areas of the country I have seen this stuff freeze to a block of ice in walls, also after years it will settle down in the walls, when I have to remove a ceiling and this crap comes down on your head it's a bitch to say the least. if I was you I would look at blowin foam instead of the cellulose.

James Boyd

I see foam used and sprayed for soundproofing. I asked about this a while back and found that foam isn't "fluffy" enough. Not "open". It turns out that standard fiberglass or cellulose is about as good as you're going to get, according to tests. I love the price, too

These happen to have been interior walls, also.

James

troubleseeker

I have never opened a wall with cellulose where it had not all settled to the bottom half of the cavity.I believe the wet spray installation is a little better because there is some kind of glue/binder in the mix, but it's a subbed out trade and now adds to your cost., especially for a small job. Since most sound is transmitted through solid materials that connect both sides of the wall (studs) , I still begin with a 2x6 top and bottom plate and stagger the studs on each side of the wall. Insulate with fiberglass woven between the studs , add 5/8 drywall , and you have a decent wall.For a little more $ strap the studs horizontilly with "hat channel", readily available at drywall suppliers, and attach drywall to the channel. For a few more $ add a layer of sound board into this sandwich and you have a serious wall.

James Boyd

The walls I dealt with were existing and un-insulated, and drywall removal was not an option the customer cared to endure. The walls needed insulation, even if slightly settled. The staggered stud (decoupled) walls would have been better, but again, not an option in that case.

Just a comment on your wall troubleseeker. If you stagger the studs you have de-coupled the wall. The Resilient Channel or Hat Channel act to de-couple also. Once a wall is de-coupled, you won't see any additional benefit from further de-coupling. This has been lab tested. So save your $$ and be glad you have a great staggered wall.

The soundboard also de-couples a bit, adds a bit of mass, and adds a bit of absorption. But it does everything just a bit. It's an old favorite in sound isolation, but the lab reports on it confirm that it only works "a bit".

James

James Boyd

As Troubleseeker pointed out, there are two ways for sound to get through a wall:

By direct contact with the studs drywall-stud-drywall

By shooting through the air cavity between the studs.

Decoupling a wall with resilient channel or staggered (or double) studs is great for the first point, but does nothing for the second point. How do you minimize the sound shooting straight through the air cavity? Insulation is only useful in higher frequencies (high notes) like voices. Not very effective for lower music and traffic sounds.

The biggest breakthrough in the last 5 years has been the idea to damp the drywall itself. This is what QuietRock, Supress, Quiet Glue and Green Glue do. Eliminate the drywall from ringing.

akabubjr

Very interesting ideas. I've alway been happy with fiberglass insulation and rc-1 (or resilient channel). But I'd like to try Quiet glue? What is that concept?

James Boyd

The insulation is not effective in the bass area... the low notes. T Insulation would be OK for high voices, I guess.

RC or resilient channel is used a lot, but I saw it as a liability. While I don't know anyone who has been sued, I heard enough stories about RC failing by sagging or short circuits. And even properly installed, it stillhas poor low frequency results. There are a lot of lawsuits around these installations. One lawsuit and I'm dead. So I avoided that route, even though I've used it before.

My customers want to stop sound from stereo. Instruments and home theaters are in that same group. All produce lower bass. So it seems to me that you have to stop the bass and the rest will be taken care of.

To stop bass, from what I've found, you have to damp the drywall or subflooring panels. This requires a damping material. Quietrock and Supress make a pre-damped drywall that is made from two sheets of standard drywall or cement board + a damping glue. It's mucho $$ at $120 a sheet, though.

You can buy Green Glue and Quiet Glue in tubes and build your own damped wall. I tried Green Glue and was very happy. I was going to try Quiet Glue next, but I haven't found anyone that's used it and then I read this on a home theater forum: http://www.avsforum.com/avs-vb/showthread.php?t=736890

It seems that Quietglue doesn't perform as well. I'm happy with the greenglue, so I'll stay with that for now. I get my contractor discount, and me and my guys can install it fast.

mad drywall

here in Manitoba we have been using insulation call roxal its dence and works well. We did a theater that had 8 seperate theaters in it and it worked well. mind u we had to double the drywall ,stagger the joints and accoutiseal the joints but when tested it worked.