"sound proofing" a common or shared wall

Ronan · Post by **Ronan** » Wed Sep 24, 2003 3:26 am

This has probably been answered on this board, but I have not found it yet.

The control room of my new studio space shares a common wall with another business. I think the current wall is just wood frame and dry wall. I can barely hear their TV from my side of the wall. The wall we share on my side is about 9 feet high and 21 feet long.

I am looking for suggestions of the best way to build a secondary wall to keep my loud mixing from bothering their business. For what it is worth, the front of my control room has a big window and a door out to the street and I am planning on putting ip a wall there as well that would cover the whole existing wall including the window and door (I have two other doors into the studio) That wall is about 9x17

Since we also share a common ceiling/roof, am I kidding my self that I will be able to cut down a lot of sound transmission, just by building a new wall?

knightfly · Post by **knightfly** » Wed Sep 24, 2003 11:19 am

Yes.

That was the short answer - John should get a kick out of that, 'cause I almost NEVER give a short answer... See, it's getting longer already

If you share a common ceiling/roof, you may also share a common floor - either way, you need to isolate the "noise" you make from ever reaching those common surfaces, since any sound that does reach them will travel inside the structure and then re-radiate into the next room, converting back into airborne noise.

If you're mixing really loud (not really a good idea, other than "wowing" a rock star client briefly) you'll want more isolation than can be had with improving just the wall. Sound follows the weakest path, whatever that is.

Your only hope for really good isolation would be to float a floor, build walls on that floor, and suspend a ceiling inside those walls using resilient isolators on each suspension wire, caulking everything with acoustic rated caulk - done right, including sound locked doors, you can thrash live drums into dumpster filling and not worry about the neighbors... Steve

Post by **John Sayers** » Wed Sep 24, 2003 1:52 pm

that's getting close to the shortest post ever

Ronan · Post by **Ronan** » Wed Sep 24, 2003 3:11 pm

Thaks for the response knightfly. Luckily my neighbor is a bar that makes a bit of noise themselves, so it will be OK if I am not 100% sound proofed.

I am considering building a wall that is basically a frame with dry wall and and air space probably filled with insulation and suspended off the floor and adjoining walls with Neoprene. I would fill in the open spaces with sound caulk or a layer of sound board.

Could I expect this to have any significant reduction of sound transmition between my control room and the buisiness on the other side of the wall. Are there any things that I could change or specify that would improve the reduction of sound transmission?

Thanks

knightfly · Post by **knightfly** » Wed Sep 24, 2003 10:16 pm

You want to watch what you add to existing construction - You need to consider EVERYTHING that's between you and the bar. If there's ALREADY two leaves (centers of mass) and an air space between, then adding yet another air space will likely REDUCE the amount of isolation.

Can you find out EXACTLY what's already there, and how/how tight it's constructed? As much detail as you can find out, then we can recommend what to do from there... Steve

Ronan · Post by **Ronan** » Thu Sep 25, 2003 7:21 pm

This site is a Godsend. I need to get around to making a donation to make sure this stays up and running. Will be the best money I ever spent on my studio.

So I drilled a big hole in the wall to see what was going on (now I need to figure out how to close it) You are indeed right knightfly, there is an airspace.

The wall between us, on my side has a layer of one inch drywall and a layer of 1/2 wood panel facing my control room. The wood panel seems to be solid wood. There is an air gap of aprox 6 inches between my wall and my neighbors. The drywall seem to be mounted directly onto 6 inch wide studs on both sides. I am guessing the studs are at about 4 foot intervals.

The wall of my neighbor apears to be similar, but he has some mirrors and dart boards etc attatched to his.

The bonus about all this is that if it gets too frustrating I only have to walk about 15 feet to start drowning my sorrows!

knightfly · Post by **knightfly** » Thu Sep 25, 2003 10:20 pm

Donations are always welcome - you'd be amazed at how few we get.

Your wall construction sounds typical for commercial space - the 1" gypsum gives a "2-hour firewall" - However, 4' centers for studs seems hard to believe. Must be either that one got left out, or not a big enough hole to tell for sure...

To patch your hole, once you're sure you don't need it anymore - I'll have to get back to you when there's time to explain this, gotta go to the salt mines in a couple minutes... Steve

Ronan · Post by **Ronan** » Fri Sep 26, 2003 3:39 pm

Steve, how right you are. My highly scientific knock on the wall and guess research has proven highly inacurate.....So I borrowed a stud finder:

The studs are at intervals of about 15-16 inches

BTW, it does not look like a situation where I could tear down the existing wall, so I will need to build something in addtion to the existing wall.

Ronan

knightfly · Post by **knightfly** » Fri Sep 26, 2003 5:15 pm

Yeah, 16" centers is more normal - so you have 1" sheet rock plus 1/2" panels on either side of 2x6 studs on 16" centers - should be a pretty solid wall already.

Here's what I would do in your case -

1. call some insulation contractors and get estimates on having the entire wall insulated with blown-in cellulose. They will have to cut a couple holes in each stud cavity (every 16") - blown-in cellulose reportedly has a pretty high sound isolation capability, so this will help several dB, probably around 8-10 just for that.

2. Patch all the holes (or have them do it, if it's part of the deal) - make sure the patches are airtight and solid.

3. Ask the same contractor if they sell acoustic rated caulk - don't accept any substitutes. There are several brands, such as USG, Owens Corning, etc - Thoroughly caulk every crack, corner, seam, etc, in the existing wall.

4. Find a sale on sheet rock and buy enough to put 2-3 more layers of sheet rock over the existing wall - different thicknesses for each layer will help also. The way you attach these layers is CRITICAL - NONE of the new layers should be fastened directly through the existing wallboard and into the studs. Period. Ever. You should use the studfinder to mark where NOT to put any fasteners for these new layers - I use masking tape on floor and ceiling to mark things like this. You can write on the tape what it is, and whether to fasten there or to NOT fasten there.

More 4. You want to offset ALL joints from layer to layer, so that there are no coincident cracks in the new layers. In this case, you would want edges of panels to fall about 2-3" to one side of a stud. This is where a line of Laminating Screws should go, on 12" centers vertically. (You follow a stud with screws, staying about 2-3" to one side of the stud, and spacing screws 12" apart vertically. It would be a good idea to spread a stripe of joint compound vertically where the rows of fasteners go, this will strengthen the bond between layers. The type of screws you want are called Laminating screws, or as USG calls them, Type G (for Gypsum) - they are designed to fasten layers of sheet rock together WITHOUT fastening to studs. This is VERY important. These screws are not very commonly stocked in most places, you may have to special order them if your local drywall contractors don't carry them.

Even more 4. You want to use 1/8" spacers under each layer of wallboard when mounting it to the wall - once the joint compound and laminating screws are in, you pull the spacers and caulk. Then add the next layer. If you can afford it, I'd go with 5/8, then 3/8, then 1/2" sheet rock.

Basically, what you want to end up with is all stud cavities filled with cellulose, the wall patched, then 3 layers of dissimilar thickness sheet rock over that, with NONE of the new layers fastened directly to the studs. Their only fastening should be a glue line running parallel to and about 2-3" away from studs, beefed up with laminating screws that ONLY mount each new layer to the old. This means progressively longer screws for each layer. What you DON'T want is total joint compound coverage between layers, only a line 3-4" wide where the fasteners hold the new layers to the old. You want each individual, different thickness layer to still have its OWN RESONANT FREQUENCY. This improves Transmission Loss through the wall. NOT having any fasteners holding the NEW layers onto the old by going into STUDS, cuts flanking noise and improves the wall performance by another 8-9 dB typically. The extra mass of 1-1/2" of drywall will improve your side of the wall by another 6-8 dB, and the cellulose should give another 8, plus now you have different mass in the two leaves of the wall, so you would probably see a total improvement of around 18-20 dB. This might be even larger if there are already cracks and holes that sound is getting through, if you do a super-thorough job of caulking with the REAL STUFF.

If you have this done by a drywall contractor, do NOT, repeat NOT, let him talk you into using Resilient Channel or "furring out" the new drywall. All either of those will do is to WORSEN the sound isolation. Cruise the other posts here on wall construction and you'll find that a TOTAL of two leaves (centers of mass) and only ONE air space is the best possible use of materials for sound proofing. Period.

If you decide to DIY this, I would recommend a good book on drywall construction - there are far too many details of do/don't for me to get into here, I've tried to limit details to those that are DIFFERENT from normal construction.

Man, if this post doesn't elicit more questions, you obviously weren't paying attention...

Steve

Ronan · Post by **Ronan** » Sat Sep 27, 2003 4:29 am

Steve,
Its amazing what a great help you have been to me! I hope I will be able to return the favor some how. I have a carpenter/builder buddy that will help me with this so he will know the regular nuts and bolts stuff. I am going to try and build the wall up exactly as you recomend.

I think I have only two last question on the topic:

1) Where the new drywall meets the floor ceileing and side walls, should I try and put some small neoprene bumpers there and fill it in with aucoustic Caulk, or just hang the dry wall flush up against those surfaces?

2) If I can not get the insulation blown in right away (I may not have the money right now) and go forward with putting up the dry wall, will drilling holes into the drywall for blown insinsulation at a later date, then resealing those holes, greatly comprimise the effectiveness of the drywall?

Thanks again

knightfly · Post by **knightfly** » Sat Sep 27, 2003 6:16 am

1. bumpers, or spacers, don't have to be neoprene because they will be removed after wallboard is fastened and before caulking. You should leave between 1/8" and 3/16" gaps all around the new layers, sealing each layer with acoustic caulk as you go.

2. Yes, it will hurt isolation a fair amount (several dB) - the wall as described offsets joints in each layer and seals between layers, while still letting each additional panel maintain its own resonant frequency - If you were to drill holes clear through all this for insulation, then fill them, the plugs would be one continuous consistency all the way through. This would noticeably lower the isolation of the wall in several ways.

I'd get the insulation first, and caulk all corners/cracks - then do an isolation check (crank your system and go next door with a SLM - you should do this BEFORE you change ANYTHING, for a reference) Put up a CD with solid bass and drums, crank it til it's where you think you'll normally mix, take it to the next higher dB mark on the meter (C weighted, fast) - say, 90 or 95 dB peaks) take your readings near the party wall and record all settings. (Be sure and tell your neighbor you're going to do this FIRST) Then, go next door and measure with the SLM set the same, except probably lower range (hopefully) - note these readings also, including exactly WHERE in the room you took them (this will need to be done at the quietest time of the bar's day, for consistency)

Then do the first step (insulation blow-in and re-seal) - same test, write everything down and compare) - make this same test (exactly the same, same CD, same song, same levels, etc, or it doesn't mean anything) - every time you add something. You may find that 1 or 2 layers of sheet rock will do the trick in addition to the insulation. No point spending any more on this than necessary, especially since we don't know how much effect the common ceiling is gonna have.

One thing on the ceiling - if there's a way to check above the ceiling, it wouldbe good to know what's there. You may be able to lay in heavy insulation there also, and damp the ceiling. That would help flanking noise somewhat... Steve