[behengold]

I’m building a 16x14 theater in my basement with 7’4’’ceiling height. Two walls are exterior. Ceiling options are limited. Should I double sheet rock both sides of interior walls which in effect gives me four layers (2 inside theater,2 outside) or two on one side one on the other. Do I need to do double rock on exterior walls as well. Thanks for your help.




Andy

 

[mchil]

I'm not sure about the drywall question, but I installed QuietZone insulation in my interior walls and ceiling joists... I got it from Home Depot. You may be planning to use insulation already, but I didn't see it mentioned, good luck.

 

[wesM]

do it in this order:


insulation between joists

sound board OR roofing felt attached to joist

resilient steel channel perpendicular to joists direction

drywall

 

[David Luks]

Andy,


You may want to us accoustical insulation like Roxul mineral fiber. Much better properties than regular insulation.

http://199.202.236.133/usa/product_details.asp?id=35

 

[mchil]

Wow Dave, that is some cool stuff, any idea what it costs?

 

[Chris Otto]

Even better, where did YOU get it Dave? You're a hop, skip, and traffic jam away!

 

[behengold]

Thanks for the reponses. It sounds like insulation of some sort in the interior walls is a good ideal. I'm still not certain if this should be done in addition to double sheet rock or will allow me to use a single layer. Also, do the exterior walls require different sound treatments then the interior walls ?



Thanks again,


Andy

 

[settopguy]

You probably should treat all the walls the same way so the sound reflects the same way from all walls. If some are one layer while others are two then the one layer walls are less stiff and have less mass. They will behave differently than the double-layer walls.


Furthermore, the single layer walls would allow more sound to pass through into the cavity between the joists where it will tend to resonate. To reduce the chance of unwanted resonance, a double layer on all walls is preferable.


As for the need for double layers on the other side of an interior wall. It depends on what the other room is used for. If you want a bedroom right next to a home theater, then you may want to do more than just double layers of sheet rock on both sides of the wall. You may want two separate walls that are not touching. Or a poured concrete wall in addition to a wall filled with insuluation and two layers of sheet rock inside the home theater. I would suggest just putting two layers of sheet rock in the home theater, and one layer on the other side of interior walls. If you need to add more layers or walls in the future, then deal with the cost and trouble later.


You also have to think about any path for air to leak out of the room. Sound can be carried through air ducts, metal conduit, pipes, and other rigid parts of the structure of the house. Caulk around every switch plate, electrical outlet, and other hole. Try to make the room air tight, but still allow for a source of fresh air so you won't suffocate.


If you used air ducts for A/C or heating, then it is better to have a separate heating/cooling system for the home theater to reduce the chance of sound reaching other parts of the house through the ducts.

 

[rgladiator]

Home Theater Mag. has a good article on different types of wall construction:

http://www.hometheatermag.com/showarchives.cgi?140:1

 

[CV63]

Remember that while insulation in the joist cavaties is important to avoid the possible resonant cavaties, it wont do much to soundproof the room.


Bass flows through insulation like prune juice thru an old man.


Mass = soundproofing.

De-coupling = soundproofing


So either use a de-coupled wall method ( might not be good with your low ceiling ) or go the mass route.


The extra sheetrock will help and you can use products like this to help add mass without taking up too much space:

http://www.silentsource.com/barriers-soundbarriers.html

 

[mchil]

That's an interesting article, rgladiator. It seems to contradict the general opinions of this board regarding subfloor construction, though..(I know this thread is about walls, but nonetheless)


Most members suggest filling the void between the concrete slab and wood subfloor with a dense material such as sand or insulation? The article suggests that you get better bass response and resonance with this void kept empty. Does this change anyone's thoughts?

 

[usabrian]

I think your mixing up floors and stages. You would not want to fill the floor with sand because it would be as dense as concrete. It would then probably be a waste of time. A stage on the other hand is a potential big bass drum.


Brian

 

[mchil]

Ah, thanks Brian.

 

[BGPGuy]

What is your ceiling going to be? If drop ceiling, not sure how much good the double drywall will be. Some people lay drywall on there drop ceiling tiles to stop rattling. Not sure I would go double drywall on poured concrete walls and other walls if ceiling is just drop tiles. If sound passes up through ceiling....


In mine, 2 walls face foundation, 1 wall basement, and another stairs/basement. I followed the advice of others, and did the floating ceiling, decoupled walls, and double drywall. I even built a second wall in front of my stair/entrance wall, for a totally decoupled room-in-a-room. I don't care if sound in the adjacent basement room is heard, as long as it stays in the basement, so did not double drywall other side.


Double drywall has it's problems, but is worth it. Watch out for outlet boxes, use box extenders if possible instead of blocking behind box (depends on if you go insulshield or not for absorbitive below ear level, 2 1/8" beyond box extender reach I believe). The floating ceiling joists with double drywall made can light insertion difficult as well.


If you need to isolate sound as much as possible, this is the best way. Acoustiblok may be better, but it aint cheap!

 

[BGPGuy]

Good reading here too.

http://www.acoustics101.com/


I wonder how dual drywall layer can be such a small increase in STC value over single layer though. Anyone?

 

[Dennis Erskine]

STC values are a 'weighted average' based from values measured at 1/3 octaves. Thus, the STC value may not be telling the whole story and you're getting more benefit at certain frequencies than the STC delta would lead one to believe. It makes linear comparisons rather suspect.

 

[Chris Otto]

We definitely do NOT live in a linear world. Despite what NASTRAN or other modelling software developers may try to tell you.


Does the acoustiblok/roofing felt provide that much more mass?

 

[Dennis Erskine]

Roofing felt does not add much on the mass side...it serves more as a mechanical isolator...at least until you run nails through it. Acoustiblok is a more dense, non-permeable material, which provides some low frequency absorption. It appears to work best when "draped" through the wall. IE, it can move as a membrane.

 

[mgabbard]

Dennis is right. I think many people confuse 'roofing felt' for 'roofing rubber' when talking about adding mass to their walls.


The felt has really no density whatsoever, but the rubber is extremely dense (read heavy). It's also a good alternative to Acoustiblok type materials and much cheaper. And when applied properly it can help dampen resonating drywall as well as help to create airtight voids behind your wall.


I have done this in my home theater (along with a few other techniques) and have been able to get sound isolation approaching room-within-a-room levels with far less $$$, no double drywall, and much thinner walls. I have been blessed with having my furnace located right behind the wall where the sweet spot in my home theater is and I can be physically less than 3 feet away from the furnace through the wall and have no idea it's on. The motors on my LD and DVD players located further away are more discernable.


...M

 

[shajan]

Mgabbard, is rubber roofing the same as rolled roofing (which I already purchased)? Where did you buy it and what's the cost? Will my asphalt rolled roofing have similar characteristics?


Thanks.