Acoustic batt instalation Help

[mrad68]

Hi guys, I am new to the forum and was hoping to get some advice on installing acoustic insulation batts in my walls.
I have a dedicated home theatre room which measures 5.6mts x 4.2mts. After years of listening in this room I have decided to do some treatment in my walls, as I was never happy with the sound and vibrations coming from the walls. I am at the stage where I have removed all the internal plaster and have the studs exposed. My studs are 90mm deep, and I have managed to get my hands on some rockwool acoustic insulation rated at 60kg which are 50mm thick. If I was to place these batts in, it would give me an air space of 40mm, is this ok. Or I could putt a double layer in and widen my stud to accommodate, Would this option be better. Basically my Question is how much air space,if any do I leave between the plaster and batts. I hope this makes sense but it is to my understanding that there should be an air gap to reduce vibration going through the wall.
Cheers guys any thought and feedback would be appreciated.

 

[JohnnieB]

If this is on any exterior wall, don't forget your moisture barrier. In order to reduce vibration transferrence, use a foam board between the stud and drywall. I wouldn't worry about the dead air space.

 

[GO-NAD!]

Do you want to reduce sound transmission to other rooms, or just attenuate the vibration of the walls inside the room? Since you say that you have "batt" insulation, I assume it's the soft compressable kind and not the rigid kind? If that's the case, I would fill the wall cavities completely. I don't think squeezing 100mm of insulation into a 90mm space will be of great detriment to its acoustic properties - but I'm not an expert, so don't take that as gospel.

If your walls were vibrating badly, I would do a thorough inspection of the studding to ensure they're all tightly secured in place. If you're walls were covered with plaster, I assume the studs also had lathes attached? That could be a source of the vibration as well. Will you be using sheet drywall to cover your studs? If so, that may stiffen things up. You could even put a double layer of drywall on, separated by acoustic adhesive, like Green Glue.

 

[psbfan9]

Hi Mrad68, Welcome to the forum.

Are you using floor standing speakers? Are you using a sub woofer? What type of flooring do you have in the room? You may want to consider decoupling the speakers from the floor with pads or cups to reduce/remove vibrations from the floor. There are a numerous pads and cup type things you can try. Aurelex may be the best known brand for pads.

Auralex

Here's an article that may help.

http://www.genesisloudspeakers.com/whitepaper/Genesis_Loudspeaker_Coupling_Decoupling.pdf

 

[mrad68]

Hi Johnnieb, my room has two external walls and two internal walls. I have a foil type insulation for moister barrier .The foam sounds like a good idea I will defiantly look into it, thanks for the tip.

 

[mrad68]

Hi Go-nad thanks for your response, My first priority was to reduce the vibration inside the room and hopefully improve sound quality within the room, As my walls were hollow and not much glue was used on the dry wall to stud as I found this out when removing it. It virtually fall of the studs. I’m hoping with a more dense solid wall things will improve. The batts I will be using are a very good quality, rated at 60kg and are quite dense which should also help reduce sound transmission to other rooms which is an added bonus. Once the room is complete I will be looking into some bass traps and wall panels.

 

[mrad68]

Hi psbfan thanks for your reply, yes I’m using mirage om7 floor standing and 2 om200 subs and the floor is a concrete slab. I have a raised rear seating which I built out of timber framing and chipboard flooring. The mistake I made is I left it hollow. But I will be filling it with some acoustic batts . My local hifi store suggested I fill it with sand which I think would be the best filling for it but I don’t like the idea of bringing to meters of sand into my house.