Axiom Home Page Forums General Discussion Advice from Axiom Owners acustical advise?

I need some advise on acustics and sound proofing. Heres the 411: My HT is in the basement. It is aprox. 14'wide x 36' long ( the theater portion is about 16' long the rest will be a game room) x 7' tall. The two short walls, one long wall, and the floor are concrete. I plan on boxing it all in with 2x4 wall construction, filled with insulation, and coverd with drywall. drywall for the cieling and carpet for the floor. Front projection screen on the short wall, projector 16 to 17' from screen, and couch about 14 to 15' from the screen.

Questions:
How would I go about sound proofing the cieling from the upstairs. If you are downstairs you can hear people walking around upstairs. I thought about geting some styrafoam and puting that between the rafters along with some insulation.

Also thought about haning a sliding curtain with some heavy fabric to seperate the game room from the HT. Not too woried about insulating the sound between them as much, but kinda thought it would help with the acustics.

Last but not least, should I use fabric on the walls and ceiling? I thought I read somewhere that it would help with the acustics and the souround in the room.

Any thoughts would be appriciated.

Timmy

You were in a similar situation to me. For basement insulation questions, I would visit http://www.buildingscience.com/resources/homeowner.htm
They seem to have approached the issue scientifically if you can imagine that!

As for acoustics, there is a lot out there explaining how you can install metal channels that keep your drywall away from the studs. I went lower tech. First, for my concrete walls, I followed the advice of the Building Science guys. I put rigid pink foam against the concrete. Then, I installed 2x4 studs (lying flat) against the concrete so that the wood studs do not touch the concrete. They are attached with Tapcon screws through the pink foam. In addition, between the studs, I installed more rigid pink foam. On top of all that I installed 5/8" drywall. The result is very solid feeling outer walls (i.e. if you pound on them, they sound solid and not hollow).

The left wall separates my basement into two halves. On the other side of the wall from my HT, are all my utilities, furnace, blower, etc. I built that wall as a standard 2x4 frame. Between the studs, I stuffed fiberglass insulation (but with NO paper backing because it is not necessary because it is not an outside wall). I used 5/8" drywall on both sides of this wall.

For the ceiling, with only a 7' ceiling to work with, you'll probably have to go with drywall (as opposed to a hanging ceiling) like I did to meet local minimum height codes. Again you can use metal acoustic channels to keep the drywall from the joists. Instead, I went with a product called Homeosote between my joists and 5/8" drywall. I was able to get Homeosote at HomeDepot. Its a lightweight fiberboard type material that is supposed to be good for that. Its a pain in the a** to work with and you must use a mask or something.

How does it all work???

Well, overall, I would say the room is somewhat 'bright' in that it doesn't absorb the higher frequency sounds. It is still smooth, flat drywall all around afterall. I would like to try some acoustic panels (e.g., simple fabric covered material) on the walls to try and decrease the brightness sometime but that's down the road.

The wall between my HT and furnace area works great! I can barely hear the furnace and blower which are less than 10' from my HT sweet spot.

The ceiling works ok as far as I can tell too. You can certainly hear loud low frequency sounds upstairs but its not that bad.

This is a quick summary and I'm sure I'm forgetting some things but I'm busy listening to the Cleveland Browns loose again.

Good luck and let me know you have any more questions...

Here is a link to a pdf from a site that pushes its own products, but it is still informative otherwise.

http://www.quietsolution.com/Home_Theater_v5.pdf

psychobabble,
Thanks for your reply. I checked out the links you refered me to. The first site building science was for weatherproofing and insulation. The second site, quiet solutions had some interesting products but were out of my price range! If I were to go with a standard 2x4 wall construction on the two concrete walls would the sound be affected by the hollowness of the walls, I mean the sound would go through the sheetrock, through the insulation, and hit the concreate. Would it resonate off the concrete back into the room? I may be worried about nothing here, I mean, I don't know if this would create a problem I could hear or not. (I am just an average person who problably couldn't tell the difrence between a 10,000 dollar speaker and a 100.00 one.) I guess I was more concerned with the ceiling. The floor joist's in my house are 2x12 which gives me more air space between them. If I put regular batting insulation in I still have air space. You mentioned metal chanels to seperate the sheetrock from the 2x4's and the rafters, what do you mean by this? What does the space between the sheetrock and 2x4's do for you?
I know I am not going to be able to completly sound proof the room because it is not completely enclosed. I mainly want to try and control the sound between floors.

Any cheap and inexpensive tips and tricks to acomplish this?
Anybody got anymore links to sites other than the ones already mentioned?

timmy

Yea, the first site is mainly for thermal insulation. I live in the Chicago area and insulating the outside walls for warmth is a must.

If I remember correctly (anyone else can chime in) what you DON'T want is completely hollow walls, including the outside concrete walls. So, if you put 2x4 studs on the outside walls, you probably want to fill it with something, either fiberglass insulation or, like I did, ridgid pink insulation (for reasons listed on the first site).

For inside walls (and ceiling), sound is transmitted in at least two ways. First, it is transmitted by the actual building materials (ceiling drywall, wood joists, plywood floors,etc.) The metal strips (I think the second site mentioned them) are to dampen the transmission of sound from the drywall on your HT's ceiling to your floor joists. The metal strips are V-shaped and flexible and so absorb some of the sound energy from the ceiling (kinda like springs). Is the floor of your upstairs carpeted? The carpet will help absorb some of the energy from your floors -- mine is hardwood

The second way sound is transmitted is through air spaces between your HT ceiling and the upstairs floor. This is where the fiberglass insulations helps. If you do use it, make sure you use the kind that has NO paper (vapor barrier) on either side. The paper vapor barrier is only when you are using to actually insulate (for warmth) between a living (climate controlled) space and an uncontrolled space. I'm assuming you'll heat/cool your HT.

The Homeosote material I used was supposed to help dampen BOTH sound transmission methods but only A LITTLE BIT for both. I didn't want to use fiberglass to create a thermal barrier between the basement and upstairs. I forget why I didn't go with the metal channels, maybe it was simply cost?

I measured sound levels in my furnace room (furnace on) and it registered about 75 dB. In my HT (furnace on), it was at or below 50 dB depending on where I was standing -- note, besides the walls and spaces between the walls, in an actual house, sound is also transmitted via other means, e.g. through heating ducts. I then turned on my system's pink noise to about 80 dB and took my SPL upstairs, directly above it (hardwood floors remember). It was also at or below 50 dB. It was not surprisinglingly a little higher (but still less than 60 dB when I used my sub only). Again, sound was coming up through the metal heating ducts more than anything. In the room directly above my HT system, I can definately hear the sounds but they sound a little muffled (I would probably get annoyed if I were trying to read in there or something).

Note also that my thermal insulation on my outside walls works very well! I have to keep the heating ducts in the HT room closed or it gets way too hot. (in case you have to worry about that too)

I am an architect. Here is what I would recomend: Walls: 2x4 studs 1/2" for concrete walls. Insulate with fiberglass batts with paper vapor barrier & sheet rock. The suface of the finished sheet rock will be what affects the sound reflections far more that anything else. Fiberglass batts behind will more than deal with any other sound issues inside the walls. The insulation is more for comfort in heating the room but will inhibit sound transmission in the house somewhat.
Ceiling:
The real issue is the ceiling. Go to a good building supply business one for contractors rather than home onwners. 1)Buy accoustical caulk and seal all cracks and joints in the subloor you see above you. Assuming the subfloor is plywood this is feasible. Run beads in the corners where the floor joists and subfloor meet and at any other joints. 2) Get some "rebond" type carpet padding, the type made from little chuncks of dense foam rubber bonded together. You can buy this new from carpet supply house or flooring company. You can also probably get it free used from carpet installers when they do carpet replacements. Cut it into strips about 6" wider that the overhead joist bays. Staple it up against the subfloor and wrapping down about 3" on the sides of the floor joists. 3) Fill the joist bays with 12" high density fiberglass batts without paper facing. 4) Using drywall screws, fasten sound deadening board to the bottom of the floor joists. Sound-deadening board is 1/2"x4'x8'fibrous material, not very heavy or expensive. 5) The metal strips refered to in other posts are called resilient channels. Screw them 16" on center perpendicular to the floor joists, to the floor joists through the sound-deadening board. 6)Screw 5/8" drywall to the resilient channels. Finnish all the dryall with paper tape & joint compound.

Ceiling drywall should go on before walls are drywalled. After painting you will have moderately reflective standard wall surfaces. At this point you can add whatever other surface treatments you want for esthetics and reflection dampening. Each of these steps is independant and will dampen sound transmission more. They are about as inexpensive methods as you can find. Hanging 5/8" drywall on a ceiling and drywall finishing are the only real challenging parts. Finishing drywall is skilled work but not terribly so. The fewer direct paths through air you leave the less sound leaks you will have. Fiberglass batts come in different thicknesses and densities. Use high density 12" batts in the ceiling. You should go to an insulation company directly for this material.

MD, thanks for stepping in. I wish I had gotten your input before I did my ceiling. I couldn't find acoustical caulk anywhere. I think Homosote is a brand of "sound-deadening board is 1/2"x4'x8'fibrous material" correct? It was the only thing I could find. I was worried about creating a thermal barrier between my basement and upstairs. I guess it wouldn't have been a problem, eh?

One thing I'm curious about is if you took a look at the Building Science pdf about basement insulation. They come out against fiberglass insulation for outside basement walls. (http://www.buildingscience.com/resources/foundations/basement_insulation_systems.pdf) Just wanted your thoughts.

Oh and one useful bit I can still add is that when hanging the drywall on the ceiling go to a local tool rental (Home Depot worked for me) and rent a special contraption that helps lift and hold the drywall in place (forget the name). It is a true blessing and the ONLY way to go!

md55 and phycobabble,
Thanks for all the help, I think I got a handle on it now!

will keep everyone posted on progress and results!

Thanks again!