Concrete or timber first floor for cinema soundproofing

soldsold

I have read a great deal about soundproofing but there is very little available about hollowcore floors.

I am planning a cinema room over the living room in a new extension, and I know I can get the performance I need from timber first floor with double plasterboard below on resilient channels to block sound, but I cant seem to find out if hollowcore will give better performance, especially keeping subwoofer bass from passing down below.

I like the idea of hollowcore as it feels solid, no creaks, no movement so less plasterboard ceiling cracks, its currently fairly cheap to install (28 euro per m2 or so), it gives a good base to work above when building its and easier to get airtight than timberframe.

But will hollowcore prevent low frequency subwoofer sounds better than timber flooring due to its mass, or will it act like a drum?

Anyone with a scientific, proven reply? ie

Thanks,

Steve

CmX

I'd be interested in finding out more about this myself as I plan to have a recording studio upstairs/attic

spadder

I would suggest open cell foam or rockwoll on the timber frame floor with, insulated plasterboard on the cinema roof. I've see open cell foam pumped into aluminium window frames to reduce road noise in an office block, worked very well.

soldsold

Thanks for the replies.

Here is what I know so far that is proven to work:

Sound travels either through a structure or around a structure. Mass and/ or isolation stops sound from getting through but softer absorbent materials (glass wool) can also stop it bouncing around. Rockwool is good as it absorbs but also has some mass. Concrete and plasterboard also good. Sound gets through the smallest holes so caulking and detailing is very important.

ISOLATION NOTES:

1) Aim for a "room within a room", where the cinema floor is suspended off the first floor - eg using staggered double joists where the cinema floor joists are raised about 2 inches higher and the plasterboard ceiling joists are 2 inches lower.

2) And/or hang the plasterboard off metal furring strips (resilient channels) screwed to the joists at right angles - to isolate the sound from the joists getting to the ceiling.

3) The walls should be of a double skin construction - standard timberframe inner leaf design spaced a few inches apart, both full of rockwool with a clear airspace between them. The floor plates should also be spaced apart so sound cant get through here.

4) The plasterboards for ceiling and floor should not touch in the corners, and should not touch the floor. Leave a small air gap all around and fill this carefully with caulk. Many home cinema builders swear by a product called "green glue", a non-hardening mastic type material that looks like tubes of silicon, squirted on in squiggles at about two tubes per plasterboard sheet on the second sheet that is then screwed to the first, sandwiching the green glue in between the sheets. Apparently it never sets and isolates the plasterboard sheets from each other. Not too cheap but its supposed to be really effective.

5) The cinema ceiling should be suspended/ double joist design also (ie also a "room within a room" design, but its probably not AS important as the sound is only escaping to outside. However some of the sound getting through the first floor ceiling into the roof will get back down if flanking sound control is not detailed in - ie sound will travel around the ceiling/ roof void and look for weaknesses.

6) Joists should be hung off the walls using joist hangers instead of being built into the walls (many sound control issues are the same as air tightness issues!!!)

7) Build a double door ie two doors instead of one - the first attached to one timberframe wall leaf and the other one to the other leaf in the double skin wall design - so there is a gap of a few inches between them. Alternatively a small lobby with a floorspace of about one metre can be built as the entrance to the room.

8) Make sure all air gaps are filled in around the door frame with expanding foam, and weatherstrip the doors around the edges.

MASS:

1) The entry doors into the room should be of a solid, heavy design. Hollowcore doors are good for energy control but bad for sound control. Use a solid exterior door in an interior frame for best results.

2) Concrete is good, double plasterboard on both sides of the walls and under the ceilings is good (make sure its staggered to cover joints in the boards. Rockwool is probably better than fibreglass to fill timber frame walls but some say fibreglass is fine.

3) Hollow core floors are either A very good because... or B very bad because.....:D

Hopefully someone will finish off number 3!

Steve

spadder

soldsold wrote: »

Thanks for the replies.

Here is what I know so far that is proven to work:

Sound travels either through a structure or around a structure. Mass and/ or isolation stops sound from getting through but softer absorbent materials (glass wool) can also stop it bouncing around. Rockwool is good as it absorbs but also has some mass. Concrete and plasterboard also good. Sound gets through the smallest holes so caulking and detailing is very important.

ISOLATION NOTES:

1) Aim for a "room within a room", where the cinema floor is suspended off the first floor - eg using staggered double joists where the cinema floor joists are raised about 2 inches higher and the plasterboard ceiling joists are 2 inches lower.

2) And/or hang the plasterboard off metal furring strips (resilient channels) screwed to the joists at right angles - to isolate the sound from the joists getting to the ceiling.

3) The walls should be of a double skin construction - standard timberframe inner leaf design spaced a few inches apart, both full of rockwool with a clear airspace between them. The floor plates should also be spaced apart so sound cant get through here.

4) The plasterboards for ceiling and floor should not touch in the corners, and should not touch the floor. Leave a small air gap all around and fill this carefully with caulk. Many home cinema builders swear by a product called "green glue", a non-hardening mastic type material that looks like tubes of silicon, squirted on in squiggles at about two tubes per plasterboard sheet on the second sheet that is then screwed to the first, sandwiching the green glue in between the sheets. Apparently it never sets and isolates the plasterboard sheets from each other. Not too cheap but its supposed to be really effective.

5) The cinema ceiling should be suspended/ double joist design also (ie also a "room within a room" design, but its probably not AS important as the sound is only escaping to outside. However some of the sound getting through the first floor ceiling into the roof will get back down if flanking sound control is not detailed in - ie sound will travel around the ceiling/ roof void and look for weaknesses.

6) Joists should be hung off the walls using joist hangers instead of being built into the walls (many sound control issues are the same as air tightness issues!!!)

7) Build a double door ie two doors instead of one - the first attached to one timberframe wall leaf and the other one to the other leaf in the double skin wall design - so there is a gap of a few inches between them. Alternatively a small lobby with a floorspace of about one metre can be built as the entrance to the room.

8) Make sure all air gaps are filled in around the door frame with expanding foam, and weatherstrip the doors around the edges.

MASS:

1) The entry doors into the room should be of a solid, heavy design. Hollowcore doors are good for energy control but bad for sound control. Use a solid exterior door in an interior frame for best results.

2) Concrete is good, double plasterboard on both sides of the walls and under the ceilings is good (make sure its staggered to cover joints in the boards. Rockwool is probably better than fibreglass to fill timber frame walls but some say fibreglass is fine.

3) Hollow core floors are either A very good because... or B very bad because.....:D

Hopefully someone will finish off number 3!

Steve

It might be cheaper to buy headphones:D

gman2k

Folks, I'm about to sound proof my ceiling in my house - Timber frame with 'eco-joists'.
I'm going to pump in insulation, but have two choices
A: Rockwool pumped in €900
B: Cellulose (recycled newspaper & fireproofed) for €2000.

My plasterboard ceilings will be 15mm soundcheck board and std 12.5mm plasterboard staggered and skimmed.
As all lights are down lights, I've created plasterboard boxes around each, and will put in some rockwool above each of these also.
Couple of questions - where can you get the 'green stuff' glue/mastic in Ireland - as I will put this in living room <cough cinema>, and also in the utliity room - to stop noise of washing machine/ dryers spreading too far.
Also, what are the thoughts on the cellulose V rockwool pumped?
Apparently the cellulose when pumped becomes quite dense.

whos_rowan

if you chose to have a suspended ceiling one way of adding sound insulation is to pour sand on top of your suspended ceiling

soldsold

First, note that green glue is not cheap, but it does appear to be effective. A discussion of "is it worth it" by home cinema builders is on: http://www.avsforum.com/avs-vb/archive/index.php/t-735720.html

Website that shows green glue ceiling options (and as many ceiling and wall options as you could want) is: http://www.greengluecompany.com/newConstructionFloors.php

edit: recommendations by pm only...

I dont think pumped insulation is best as you should leave an air gap for isolation - sound is very difficult to control and its not just a case of "put more in for better results". The web link above shows different options and how well they work. Rockwook should be fine, its usually whats recommended.

Note I dont have any affiliation with the green glue company, just from my research I know I'll be using it on my cinema room walls and floors.

Steve

mfceiling

Hi lads,

1st time poster but long time watcher.

I did a recording studio 2 years ago in cherrywood and they built a room within a room to combat the noise. Apparently walls built at right angles will allow sound to bounce around more freely ( contracts manager made us build the walls at alternate angles ). The whole internal room was double slabbed with 15mm soundbloc board as was the outside room - both sides - 8 sheets in total. I would also insulate above the ceiling with something like rockwool.

soldsold

mfceiling wrote: »

I did a recording studio 2 years ago in cherrywood

Cherrywood is not recommended for soundproofing, concrete is better

mfceiling wrote: »

and they built a room within a room to combat the noise.

Room within a room is the best isolation measure you can have. Google "room within a room".

mfceiling wrote: »

Apparently walls built at right angles will allow sound to bounce around more freely ( contracts manager made us build the walls at alternate angles ).

This is a good point. The worst room is a square. There are ideal cinema room dimensions if you search google - 6m x4m x2.4m high for example

mfceiling wrote: »

The whole internal room was double slabbed with 15mm soundbloc board as was the outside room - both sides - 8 sheets in total.

Also good advice. Most soundproofing websites recommend this as a very effective and cheap measure, however normal plasterboard is recommended as its cheaper and "almost" as effective.

mfceiling wrote: »

I would also insulate above the ceiling with something like rockwool.

rockwool is good as its dense, but I would definitely research a tried and trusted system (eg search the green glue website as it has a load of tried and tested solutions using standard building materials) rather than trying what looks good - it might not be...

boss74a

hi im having problem with noisy naibours the wall is concrete but can still hear voises and door slamming any toughts thanks

BryanF

hi this thread is ancient, note the last post was '09, best to start a new thread