sound proofing - extra layer vs decoupling

[drambitz]

good morning,

i'm about to try and soundproof a small room in the attic and i'm faced with a dilemma.

considering every cm of space counts which solution would you suggest I go for:

a) decoupling from surfaces and adding 1 layer of reconstituted rubber/drywall

b) no decoupling and adding two layers of reconstituted rubber/drywall in direct contact to surfaces

the decoupling would be done with rubber shocks to which the drywall beams can be mounted minimizing surface contact.

the rubber/drywall sandwich cuts around 35db @ 100hz to 70db+ @ 3k and over

also..

if I decoupled would it be better to:

c) leave the air space between the wall and the sandwich

d) fill the air space with rockwool

i'm going round in circles here..

what would you guys and gals do?

any suggestions would be greatly appreciated

thank you very much.

[jhbrandt]

Hello drambitz,

I really need more information in order to help you;

How much isolation do you require? What are you doing with this room? - Tracking (with drums) or mixing only.. or both?

"rubber/drywall sandwich cuts around 35db @ 100hz to 70db+ @ 3k and over"

Where did you get this information? & is there 'official' independent testing data for this?

I have yet to find anything better than good old gypsum board or cement block for sound-proofing - especially with a MAM system. (Mass-Air-Mass)

So, depending on your use, I would recommend decoupling. But only with quality, tested clip designs. Trust me, they are worth the little extra you might pay. - Especially if you were willing to pay for some gypsum/rubber sandwich.

There are several good links on my publications page with the testing data of wall, ceiling and floor configurations. If you need clips, I highly recommend RISC-01, any Kinetics, and Whisper Clips. There are others that I haven't mentioned that are good too. check em out.. find the ones with testing data and go with them.

-- And just use the fire-rated gypsum board. It's pretty hard to beat.

Cheers,
John

[drambitz]

hi John,

that's correct - i'm looking to use this as a tracking room for drums and amps

naturally i would like to get as much iso as i can without shrinking the room too much - anything that will allow me to get an acceptable monitoring environmet in the control room next door

the room, as it stands is of recent construction and complies to current local (Italy) building code

round here they use blocks/mortar for walls and concrete for floors and i have reason to believe these have a reasonable amout of insulation (heat/noise) bulit in to the structure

how it will handle high SPLs and bass is anybody's guess

the rating of the sandwich is provided by the local seller and i really want to believe it!

2cm rubber + 1.25cm gypsum = 35db cut @ 100hz



link to product: Tecno Rubber | Acustica Isolcentro, shop online

i'll check out the clips you suggested and hopefully i can get them shipped to italy

for convenience (read lazyness) i was going to get the clips from the same guy that sells the sandwich - these:

Fissaggi Fonoisolanti | Acustica Isolcentro, shop online

thanks for the links - will read your stuff very carefully before making any decisions.

so no rookwool in the air space?

thanks so much for helping me out.

[jhbrandt]

That -35db @ 100Hz is most likely marketing CRAP. I seriously question it...

Yes. You DO want rock wool in the air space.

Sent from my GT-S5830 using Gearslutz.com

[PAPAYAMON]

Originally Posted by jhbrandt

That -35db @ 100Hz is most likely marketing CRAP. I seriously question it...

Yes. You DO want rock wool in the air space.

Sent from my GT-S5830 using Gearslutz.com

let's say you've got 7 inches total airspace drywall to drywall. would you be better off with 6 1/2 inches of insulation or two 3 inch layers with a little space left between?

will the insulation itself conduct noise if it touches both pieces of drywall?

i ask this because i'm either buying 2 rolls of 3 inch or 1 roll or 6 inch.

[jhbrandt]

Go with 6 1/2". No worries there. - As long as it is the 'light & fluffy' stuff - regular fiberglass building insulation.
Studies show that coupling due to compression (cellulose fiber) reduces isolation. This can also apply to rock wool when pressed together between decoupled partitions.. .it's a no-no. But Regular building insulation (fiberglass) will do this just fine.
Cheers,
John

[avare]

Originally Posted by jhbrandt

Go with 6 1/2". No worries there. - As long as it is the 'light & fluffy' stuff - regular fiberglass building insulation.
Studies show that coupling due to compression (cellulose fiber) reduces isolation. This can also apply to rock wool when pressed together between decoupled partitions.. .it's a no-no. But Regular building insulation (fiberglass) will do this just fine.

As a clarification, the coupling will occur with any material that compressed against the leafs. It is not exclusive to mineral wool based insulation.

Andre

[jhbrandt]

Originally Posted by avare

As a clarification, the coupling will occur with any material that compressed against the leafs. It is not exclusive to mineral wool based insulation.

Andre

+1

... Again.
John

[drambitz]

Originally Posted by jhbrandt

That -35db @ 100Hz is most likely marketing CRAP. I seriously question it...

too good to be true... :(