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[Stephen Swaffer]

Thinking on my keyboard here-so what you are saying Ivan is that a change in media affects the sound more? or is just the mass of the wall that absorbs the sound energy?  Sound travels through solids better than air-so at first glance it seems contradictory that placing a solid in the path would reduce the sound level-though through experience we all know it does.

I guess the actual mechanism is irrelevant to the discussion.-since the method obviously is effective.

[Mac Kerr]

Sound travels through solids better than air-so at first glance it seems contradictory that placing a solid in the path would reduce the sound level-though through experience we all know it does.

Sound travels faster in solids than in air, I'm not sure that equates to "better". Sound is attenuated somewhat any time it crosses a barrier. From air to a heavy solid barrier will have greater attenuation than from air to a thin film membrane. Heavy walls provide better isolation than thin walls, and a double heavy wall where the two walls are isolated from each other so there are multiple barrier transitions to make is better still.

Mac

[Nathan Riddle]

What constitutes as a 'heavy' wall?

More mass? Concrete, steel, lots of wood?

Isn't that what Ivan is saying NOT to do? "limp" walls with space (air) between them.

Attached is my current understanding of an easy to create, cheap, very good acoustic barrier.

[Ivan Beaver]

What constitutes as a 'heavy' wall?

More mass? Concrete, steel, lots of wood?

Isn't that what Ivan is saying NOT to do? "limp" walls with space (air) between them.

Attached is my current understanding of an easy to create, cheap, very good acoustic barrier.

Sheets of lead make a great wall.  They are heavy and limp.

If you can't do that, then double or triple thick sheet rock is a cheap way to do it.  Glue them together.  5/8" is better.

As per your drawing, you DO NOT want the studs to share the outside walls.

You can LIGHTLY fill the wall with LOOSE fiberglass.  DO NOT put it in tight-it will act as a "conductor".

But when loose-the actual air paths from wall to wall are longer-so it acts like a larger air gap.  Not huge-but a little bit.

[Dave Garoutte]

Non-rigid materials, by nature absorb energy: steel bad, rubber good.
Making the walls air-tight is important; No leaks.

Track down this book online:
SoundProofingSecrets By Craig Williams

[Jean-Pierre Coetzee]

From my research I have done:

Two walls using wooden studs(don't use metal studs of any kind), there are "things" that exist, can't remember the name but the idea is to decouple the gypsum from the studs, you also want two layers of gypsum one laid horizontally one vertically. Complete air between the two walls, fill the walls with rock wool or fiberglass. From what I remember there is no real reason to put gypsum on the insides of the walls.

LINK

(Sorry can't remember how to make the link clickable, will edit right)

I would as I said put the "thingys" between the gypsum and the studs as well, can't for the life of me remember what they are called, idea is to space the gypsum off the studs just barely.

[Mac Kerr]

(Sorry can't remember how to make the link clickable, will edit right)

There are instructions in the top post in the "read before posting" forum.

Mac

[Ivan Beaver]

From my research I have done:

Two walls using wooden studs(don't use metal studs of any kind), there are "things" that exist, can't remember the name but the idea is to decouple the gypsum from the studs, you also want two layers of gypsum one laid horizontally one vertically. Complete air between the two walls, fill the walls with rock wool or fiberglass. From what I remember there is no real reason to put gypsum on the insides of the walls.

LINK

(Sorry can't remember how to make the link clickable, will edit right)

I would as I said put the "thingys" between the gypsum and the studs as well, can't for the life of me remember what they are called, idea is to space the gypsum off the studs just barely.

Yes it is better to put 2 layers of sheetrock on the outside of the studs vs 1 layer on either side of the stud.

The single layers can tend to "re-transmit" the sound, while a double layer provides a better "mass barrier".

DO NOT stuff the walls with tight fiberglass or wool.  LIGHTLY put some in.

BE SURE to completely seal all outlets, switches and any other penetrations in the wall.   Use acoustic caulk.  It will stay flexible longer.

Even a very small hole can let A LOT of sound through.

When placing outlets or switches, be SURE to stagger them on opposite sides of the walls.

This way there is not a direct path through the outlet boxes.

It is often the little things and the quality of the job that makes a bigger difference than some actual materials.

[John Rutirasiri]

Non-rigid materials, by nature absorb energy: steel bad, rubber good.

I thought the denser fire-rated (type X) drywall would perform better than regular drywall, no?  What about Durock?

[Lee Douglas]

there are "things" that exist, can't remember the name but the idea is to decouple the gypsum from the studs...

I would as I said put the "thingys" between the gypsum and the studs as well, can't for the life of me remember what they are called, idea is to space the gypsum off the studs just barely.

Jean-Pierre's "thingys" aka resilient channel:

http://www.auralex.com/product/rc-8-resilient-channel/

[ProSoundWeb Community]