how many layers of drywall?

[arjan]

hi guys,

i am building a studio in my shed.
there are three separate rooms: control, live room and a booth.
framing done, insulation and 2 layers of gypsum in place.
next is flooring and doors and windows.
i have some gypsum left, enough to do the live room once more.
i cannot test the isolation yet, as there are no windows and doors in it.

my question is, should i put another layer of gyp in the live room or not?
will it make a difference?
i read that doubling of mass gives you 6db more of isolation.
but only half the mass more? does that give any difference?
and i'm also sick and tired of gypsum...

[Weasel9992]

Originally Posted by arjan

hi guys,

i am building a studio in my shed.
there are three separate rooms: control, live room and a booth.
framing done, insulation and 2 layers of gypsum in place.
next is flooring and doors and windows.
i have some gypsum left, enough to do the live room once more.
i cannot test the isolation yet, as there are no windows and doors in it.

my question is, should i put another layer of gyp in the live room or not?
will it make a difference?
i read that doubling of mass gives you 6db more of isolation.
but only half the mass more? does that give any difference?
and i'm also sick and tired of gypsum...

Here...look at these wall assemblies. That'll give you a good idea of what to expect as you add mass.

Frank

[arjan]

ok, but that document only talks about 2 sheets on each side of the wall.
will adding a third sheet to only one side matter much?

[gn87berner]

go for it. it can only help.

[Weasel9992]

Originally Posted by arjan

ok, but that document only talks about 2 sheets on each side of the wall.
will adding a third sheet to only one side matter much?

It's more mass.

Frank

[Smithcok]

EDIT: Rod = smart, listen to him below.

[nosebleedaudio]

Originally Posted by Smithcok

Just remember that according to the mass Law, you are really only going to get another 6 dB of isolation per doubling of mass.

If you already have two sheets on there, you'd need two more to get 6 more dB. It may or may not be worth your while.

And the 6dB is the Best, most of the time it will be less than that..

[Bob Olhsson]

Adding a layer of fiber board and then a third layer of gypsum can make quite an improvement because it damps the gypsum.

[nosebleedaudio]

Originally Posted by Bob Olhsson

Adding a layer of fiber board and then a third layer of gypsum can make quite an improvement because it damps the gypsum.

I use it all the time, works good...

[Rod Gervais]

Originally Posted by Smithcok

Just remember that according to the mass Law, you are really only going to get another 6 dB of isolation per doubling of mass.

If you already have two sheets on there, you'd need two more to get 6 more dB. It may or may not be worth your while.

Funny the way you present this - ONLY another 6 dB..

6 dB is a doubling (or cutting in 1/2) the total sound pressure......... so if by doubling the mass you could add 6 db of isolation - that would be a tremendous help........

Next - it is the mass on the assembly that has to be doubled - not on a face....... so he would not need to add 2 more layers - but rather 4 more layers to get an additional 6 dB reduction,

Rod

[Smithcok]

Yeah perhaps only wasn't the correct choice of words there...
In retrospect, I should have read the whole thread too.

[arjan]

so adding only one layer to one side does more or less nothing?

[Weasel9992]

Originally Posted by arjan

so adding only one layer to one side does more or less nothing?

That's pretty much the case, yes. If you're looking for significant reduction you'll need to follow Rod's instructions.

Frank