Sound proofing

[Suzette]

(Yes I have searched - the only help was about sound proofing a pub cellar)

 

The situation is thus : the recording studio is on the top floor (drama school) and the large 'echo filled' movement studio is immediately below.

 

The building is old, using traditional building materials in most places. But recently the ceiling in the movement studio required replacing (many cracks and was about to fall down). I believe the old ceiling was some sort of plaster and lathe (?) material - but anyway it was very thick and caused a lot of dust and mess when it was removed - I'm glad the building manager, and not me, has to deal with things like that!

 

The new ceiling went up and looked lovely - new lighting strips and slightly lower (by about 4') than the old one. The room had a coat of paint and the floor was polished ........ everyone was happy ....... except my sound engineer!

 

The new ceiling is just a suspended ceiling - a thin ceiling tile is all that now separates the movement studio with its associated music , piano playing, a bit of singing and just general students chit-chat from the recording studio. The noise is being recorded with every radio class session at the moment!

 

So we know we need some form of sound proofing between the two spaces - but the question is exactly what and where?

 

I think we have a couple of options, but would be grateful if anyone else can think of any other options and/or give your comments on my thoughts.

 

Option 1 : lay a false floor in the recording studio and fill it with some kind of sound deadening material.

 

Option 2 : fit some sort of sound deadening material in between the suspended ceiling and the original ceiling in the movement studio.

Thoughts :

The recording studio has more accessible time during the day than the movement studio so it would be easier to work in there.

The movement studio ceiling is approx 20' high so we would have height and access problems in there.

The recording studio is half the size of the movement studio so would be cheaper to do - less area to cover.

 

Questions: (As I seem to have persuaded myself that the false floor is the better option)

How thick would I need to have a false floor? It is a normal height room so 2' is out of the question - they would be hitting their heads on the ceiling! Can I do something 6" thick?

Would I need to use proper sound material - rockwool? or can I use other (cheaper) material?

How do I work out how much sound deadening would occur with 6" of rockwool on the floor?

Should I use something other than plywood as the floor base? Is there another material that can be used for flooring that has better acoustic properties than ply but will still be suitable as a floor?

I thought about maybe filling the space with the recycled paper-mush stuff that they now use to fill cavity walls in houses. Is that a viable option do you think?

Studio Spares sells a sound deadening felt underlay - can anyone work out what dB loss a 6" false floor filled with rockwool and then the felt underlay on top would be?

 

As you can see, I'm not really sure where I should be going on this so any advice would be appreciated.

[Brian]

Floor isolation is an interesting problem - one I've had done on a number of occasions. The only way to prevent sound travelling is mass and lots of it. Rockwool is OK but is not very effective, you're better off with a proper sandwich construction using things like plasterboard, ply and gyproc.

[Simon Lewis]

Suzette,

 

You really need to contact a firm that undertakes acoustic work, or at the very least, a builder who can work to Part E - Robust Standard Details.

 

Whoever you take on should guarantee noise isolation to a minimum standard. In your case, you might stipulate that no normal activity in the dance room should be audible in the recording studio, although there are more technical ways of stipulating this.

 

It is entirely possible for you to spend a lot of money (either doing this yourselves or getting a builder without the requisite knowledge) and achieve very little improvement.

 

The money spent in getting someone with expertise will pay for itself through noise isolation that actually works.

 

I, and people like Mr Si (who earns his living in this field), can regale you with stories of inappropriate "noise reduction" schemes that cost thousands and didn't stop the noise nuisance. The moral is, get someone who knows how to do it properly :)

 

Simon Lewis

[Mr.Si]

Suzette, where are you based?

 

Ah Building Acoustics the er... love of my life! (?). And yes, like Simon Lewis said, can tell you about countless pathetic separating floor/ceiling constructions. some are shocking.

I seem to spend most of my life doing sound insulation testing in accordance with Approved Document E 2003 - Resistance to the passage of sound.

 

My boss is also part of the inspectorate team for Robust Standard Details, which is a separate thing to Approved Document E, but is yet the same field of acoustics. Robust Standard Details are constructions that are designed to outperform the requirements of Approved Document E and thus are not required to be tested under part E, but this is only relevant to New Build Houses and Flats. Anyway, that's not the issue here.

 

So...

 

Suspended Ceilings are definitely the way to go in order to combat airborne sound insulation. It does get expensive, but if it's for one room separation from it's pair beneath it only, then that's much nicer than a whole block of flats!

 

The only way to prevent sound travelling is mass and lots of it.

 

Correct. Mass is very important, as is vibration isolation.

 

The best systems when used in timber construction are independly joisted ceilings, with 2 of layers of 12.5mm sound blocking plasterboard or thicker.

2nd to that, and incredibly popular these days is using a Suspended Metal Frame (metal furring grid) ceiling hung from resilient hangers with a couple of layers of 12.5mm soundbloc or thicker. Some people have used a 19mm Plasterboard plank as one layer, with a second layer being 12.5mm or 15mm soudbloc. Dropping the ceiling will create a void - larger voids are better, as you're able to insulate against or even cancel out lower frequencies by playing with 1/4 or 1/2 wavelengths etc.

Each layer of plasterboard would need to be sealed where it abuts the perimeter walls, with a non hardening mastick aka "Acoustic Sealant".

 

The job of the mineral fibre (yes, Rockwool is mineral fibre) within the void is to stop reverbant energy building up within the void, by acting as anABSORBER. It is not an insulator, just an absorber, there is a difference which is commonly misunderstood as all the builders I've ever dealt with have called it insulation. It's good for thermal insulation, which is partly the confusion there.

 

 

There aren't many floor constructions which will cut it for airborne sound insulation they tend to help much more with "Impact" sound insulation (sound of footsteps upstairs, things falling on the floor etc being transmitted via the structure.

There's only one type of floor system that I'd ever really recommend, but it is an awkward thing to lay and you'd have to re-do all the door thresholds and skirting etc.

 

Suzette, could you give more information on the ceiling tiles you have in place?

I'm presuming they're just a lay-in grid type of mineral tile as commonly found in schools...

 

Download British Gypsum's "School Spec" document here - it has information on suspended ceilings which may be of use to you.

 

Alternatively, try just the British Gypsum Home Page

 

Hope this helps,

 

Si

[errol]

Hi,

 

The link below is a dealer in sound proofing material. If you click on to "Help Articals" there is a fair bit of information on various types of sound proofing and other information.

 

Custom Audio Designs

 

Direct links to what you may want to know.

 

Floor sound proofing

 

Ceiling sound proofing

 

Hope these may be of some use.

 

Errol.

[Mr.Si]

Custom Audio Designs are good people. Our company has had talks with Gary from there. They've passed us work, and I'd like to return that compliment.

 

They have some very useful How-to's and some good sound absorbing tiles, should anyone need acoustic absorption within a room or a common part of a block of flats.

[Jivemaster]

The void between the new suspended ceiling is "free space" in which to work, and you will be attenuating the sound at source, topping it getting inti the structure. Also politically the problem lies with a job done there not you needing to fully refit your recording studio. - Raising the floor, rehanging all the doors and windows etc would be a massive task and be seen as a total refit on your budget. Completing an inadequately done job in another room, should be seen as an over-run on their project. Unless of course you are responsible for both spaces.

[Suzette]

Thank you everyone for all the replies and helpful info.....

 

Mr Si - I am based in South West London (clapham area) and yes the tiles are your normal thin ceiling tiles dropped in on top of a suspended thin metal grid.

Jivemaster - I'm only responsible for what happens in the recording studio, but from what I can gather the company who replaced the ceiling did exactly what they were asked to do - unfortunately the building manager did not consider sound travelling when he spec'ed the job, and I was unaware of the situation until after I returned from holiday. So not really a project over-run.....

 

I will now pass all the info over to the relevant people up the chain to sort it out and find the money!

 

Many thanks

[paulears]

One thought - you mentioned they can hear people just speaking. While loud sounds and lower frequencies are normally the snags, as had been mentioned - maybe one problem is a failure of sealing around pipes, ducts etc. If they removed lathe and plaster and replaced it with simple tile, then that's a fairly high density barrier that has been removed. While you are waiting for real consultants to come and sort this out, a directional mic (video type) and a pair of sealed headphones in your recording area may help you work out where the sound is coming from. Probably the entire floor, but could simply be made worse by a direct path from one space through to the other via a hole! I doubt this will help very much as the problem may be entirely due to the ceiling removal, but it could help in the interim.

 

My experience with studio building suggests that many of the problems are due to penetration of what would be quite acceptable walls - my favourite was a 300mm sandwich type wall, on neoprene seals - with a 50mm hole drilled straight through by the fire alarm company who had to fit a strobe due to the fire alarm being inaudible in the studio! Or at least until the hole appeared.

[Suzette]

Thanks for all the help ... all the info has been passed to the building manager to try and get it sorted out! I'll let you know how we go on....

[DJUnreal]

My experience with studio building suggests that many of the problems are due to penetration of what would be quite acceptable walls - my favourite was a 300mm sandwich type wall, on neoprene seals - with a 50mm hole drilled straight through by the fire alarm company who had to fit a strobe due to the fire alarm being inaudible in the studio! Or at least until the hole appeared.

 

Sounds just about typical of afterthought add-ons doesn't it! makes me think of a lot of other things that happen the same way!