Insufficient soundproofing

cooperda · Post by **cooperda** » Wed Nov 16, 2005 4:50 pm

I have built a studio (practice space) that I am having difficulty soundproofing sufficiently. It is an outbuilding, 18' by 20' with a vaulted ceiling, built on a slab, located 70' to the nearest neighbor. Walls are 2x6 base and cap with staggered 2x4 studs. 5/8" gypsum interior walls and ceiling. Extremely tight. Conventional exterior door (steel with foam core), but laminated a 1/2" sheet of gypsum to it and drastically cut sound transmission – still needs work. I did not build double walls in order to maximize interior space, as code restrictions forced the exterior dimensions. Interior floor floats on 1” foam over slab. I have not installed siding yet, but the plan was to side it like my house, with 4x8 sheets of cedar, 5/8" thick.

Problem is lots of bass and snare coming through currently - can be heard for some distance. My desire is to have my full “Alternative Garage” Band able to practice any time without problems from neighbors or police. My kid’s bands are even louder !

Based on some research, I'm guessing I don't have enough mass in the walls. I can't lay up blocks or bricks around the exterior since there is no foundation for them to sit on. I know the siding will help, but I do not want to incur that expense on the chance that it won't be enough. There is a product on the market called NovaBrick – overlapping cement bricks about 2" thick, that you hang on the exterior wall. These generally just hang, but I could attempt to seal them to each other. I was wondering if this may help. Help would be greatly appreciated.

cyeazel · Post by **cyeazel** » Thu Nov 17, 2005 8:05 am

Do you have any room to play with on your interior before violating code? If so, adding a couple more layers of drywall(interior side) would help in addition to whatever you decide to go with on the exterior side. However, the problem with bass (low end in general) is that in order to stop it, it usually requires very thick masses and a large air space between the masses. Mass by itself will help some, but in order to reach your goals of not disturbing anyone, you pretty much need to have separate frames and two thick leaves of mass. The airspace between the frames acts like a spring and the wider, the better. Do you have insulation in your walls?

giles117 · Post by **giles117** » Thu Nov 17, 2005 8:38 am

what you didnt mention is what kind of insulating material in those walls?????

I would also consider an additional 2 layers of drywall on those interior walls.

the 4x8 sheeting added to the exterior walls will heplp out as well. If you can afford 2 layers I'd do it

will make the wall that much denser.

Post by **sharward** » Thu Nov 17, 2005 11:59 am

What's your ceiling situation?

giles117 · Post by **giles117** » Thu Nov 17, 2005 12:36 pm

sharward wrote:What's your ceiling situation?

I think he said vaulted ceiling

Post by **sharward** » Thu Nov 17, 2005 12:40 pm

Sorry, I should have been more specific.

How much mass is on that ceiling? Is it "two leaf" and are the leaves decoupled? Is adding more mass an option without overloading your joists/trusses? etc.

I just want to make sure we're not focusing solely on the walls, beefing them up an impressive degree, and forgetting to "look up" at what might actually be the source of the problem -- or, what might become the weakest link in the structure isolation-wise.

--Keith

cooperda · Post by **cooperda** » Thu Nov 17, 2005 3:03 pm

I'd rather not work too much more on the interior - it's finished and in use, and there is not a bunch of extra space. I think I may be stuck with my mistakes there, at least in the near term. The walls have 2 layers of conventional fiberglass R-11, interleaved with the staggered studs (2 ft on center inside and out). The vaulted ceiling is R-70+. 5 ft between ceiling and roof at the peak, 1 ft at the edges. The roof is shingled. All interior joints are caulked, with a heavy vapor barrier taped on all seams. No windows. I would have to check my truss spec to see how much load they can carry - ceiling is finished but I am in need of some treatment up there to knock down some feedback, so I could deal with working on that easier than the walls. I hung blankets on curtain rods around the interior, also to deal with feedback and resonance problems. Knocking down some of the resonance helped a bit with the isolation issue, with the bonus feature of being able to tune the liveliness of the room by arranging the curtains. I received a suggestion to use cement board ("Hardipanel") siding rather than, or as a layer under, the conventional siding to try to get some mass without having to go the Novabrick route. Could potentially incorporate a small air gap here. I don't think the code folks would gig me for a few inches, guessing they would for a few feet.

Thanks much for the help so far.

Post by **sharward** » Fri Nov 18, 2005 1:21 am

cooperda wrote:I received a suggestion to use cement board ("Hardipanel") siding rather than, or as a layer under, the conventional siding to try to get some mass . . .

Not a bad idea. That stuff is really dense and is (obviously) moisture tolerant.

Could potentially incorporate a small air gap here.

Small air gaps do not help with isolating low end.

Large ones do. If you did staggered stud with 5 1/2" top and sole plates, your gap is only 5 1/2". You're pretty much stuck with that. While staggered stud construction is better than not, double framed construction is far superior. The few inches it costs in square footage pay off big-time.

Now, about that attic... Is it vented? If so, then I wouldn't be at all surprised if you're having a major sound leakage through those vents. Remember the almighty mass-air-mass and air tightness rules. If your outer ceiling mass (a.k.a., roof) has big holes in it, then you're in a world of hurt.

It may be time to see some photos and detailed illustrations showing a cutaway view of your walls and ceiling. The descriptions are pretty good, but "pictures are worth a thousand words" as they say.

Perhaps one extra layer of interior 5/8" with Green Glue will not only add mass but address your pesky resonance issues. I realize you don't want to work any more on the interior, but you have a serious problem and I don't think there are any easy ways out of the box in which you're finding yourself (figuratively and literally)...

cooperda · Post by **cooperda** » Fri Nov 18, 2005 6:44 am

Concur with your ceiling assessment. The roof is vented, continuous venting on soffits, roof exhaust vents are on the side facing away from the nearest residence. No way around this one, other than a building within a building, as you suggested. I was recently working on the soffits/vents while a band was in there - didn't seem to be bleeding much from the vents when compared to the large wall areas.

I've been meaning to document my project with some pictures and design artifacts - I'll take you up on your suggestion and post in a few days.

I think I'm going to go forth with an incremental approach (driven primarily by cash flow), beginning with the cement board siding. I'm also going to get an SPL meter so that I can assess my progress and determine when I hit the point of diminishing return, as well as document where I am with regard to local ordinance limits.

If only my bank account was large enough to satisfy my engineering curiousity! Definitely an interesting challenge.

Thanks for your help.