[Rashiki]

I was thinking about tearing out the drywall in my audio room so I can fill the empty space between walls with something to absorb sound. Would fiberglass insulation help with soundproofing or are there better options? And, should I put drywall back up afterwards or replace the drywall with something else? I also plan on applying acoustic treatments afterward -- is there something I could do while the drywall is off to help with that? Or should I simply apply the treatments to the bare studs?

Thanks for your advice.

 -Rob

[Ethan Winer]

Rob,

It's not clear if by "soundproof" you mean you want to reduce sound transmission. That's the correct definition, but many people use that word to mean acoustically treat a room. The reason I ask you to clarify is because things that increase isolation between rooms make the acoustics inside the room worse. So one or the other is easier and cheaper than both.

> Would fiberglass insulation help with soundproofing <

Yes, in this one case fiberglass inside the wall helps both isolation and acoustics.

I can't help with the rest of your questions until I know how important isolation is.

--Ethan

[Captain Humble]

When I was a kid, my fender princeton reverb practice amp didn't have overdrive so the only way to get distortion was to drive it to levels that created it.  So...I played very loud.

My dad was and engineer and a DYI kind of guy.  Had his own tube tester and tweeked everything from motorcycles to electronics. When my parents built their last home, they insulated all of the walls in my room with the same rolls of fiberglass insulation used on the outside walls. My door wasn't the same as the other inside doors either.  Don't know what he had done to it but it was much heavier.

There may be better solutions, but they were very pleased with the results.
Jeff

[Rashiki]

Hi Ethan,

It's not clear if by "soundproof" you mean you want to reduce sound transmission. ...

My motivation for removing the drywall is for isolation -- I want to cut down on noise from outside and the rest of the house from entering the room, as well as cut down on "leakage" of the music in the room to elsewhere in the house. However, my primary goal with this room is to transform it into a decent listening room. I would like to improve the isolation while treating the room for acoustics, but if these are conflicting goals, then I'll pick acoustics over isolation.

From your and Jeff's comments, it would appear that putting some fiberglass between the walls would help to isolate the room, but once I have the drywall off, should I put new drywall back on and then apply acoustic treatments on top of the drywall or are there better choices for improving the acoustics of the room? Here are some options that I have come up with:
1. finish wall with new drywall
2. finish wall with wood panels or strips
3. finish wall with fabric, foam or some other material

Any suggestions?

 -Rob

[John Ashman]

Rob,
    After insulation, I put 1/2" sheetrock on the wall, then glued (liquid nails, smeared) celotex panels on, then glued 5/8" sheetrock on top of that and screwed the hell out of it, then used heavy, hand-trowled venetian style (ish) plaster on top of that.  There may be better ways of stopping sound, but this does pretty darn well.  I haven't done the ceiling yet, so when the guys at Subway are moving their mop bucket across the tile floor, it doesn't come through the wall, it goes OVER it and it freaks people out because it sounds like a herd of squirrels running across the roof

[Curt]

I was thinking about tearing out the drywall in my audio room so I can fill the empty space between walls with something to absorb sound. Would fiberglass insulation help with soundproofing or are there better options? And, should I put drywall back up afterwards or replace the drywall with something else? I also plan on applying acoustic treatments afterward -- is there something I could do while the drywall is off to help with that? Or should I simply apply the treatments to the bare studs?

Thanks for your advice.

 -Rob

Rob,

To "soundproof" a room I like to use 90Lb tar paper (the kind used for roofing) cut and glued inside the wall (on the inside of the outside piece drywall) then fill between the studs with fiberglass, then reinstall the new room drywall (put some caulk on the studs first).

When you have the walls apart you can caulk the outside piece of drywall to the studs to avoid vibration noise. Drywall screws, not nails, work best to fasten the drywall to the studs.

The room's interior drywall finish should be planned together with the room treatments, listening position, and the desired reverberation time.

A good book to read about some of these things is:
"Master Handbook of Acoustics" by F. Alton Everest.

That said, a lot of experimenting will also be required. Have fun.

[John Ashman]

Oh, yeah, and I liquid nail the hell out of the studs before I put the sheetrock on so that it not only acts as a buffer, but it keeps it from vibrating against the wood.  Liquid Nails is your friend

[bpape]

To best balance isolation from the outside while retaining the positive acoustical benefit INSIDE the space, put in the insulation and then double the drywall on the OUTSIDE of the wall.

This allows the drywall inside to act as a resonant panel trap for bass while still providing some isolation to/from the outside.  If you double the inside, be prepared to deal with extra bass absorbtion needs INSIDE the room as the walls will no longer provide much in the way of bass control.

[John Ashman]

What if you put grills in the wall in various places?  Could you, at that point, use the internal spaces as a bass trap?  Defeats the isolation thing, but...........

[Ethan Winer]

Rob,

> if these are conflicting goals, then I'll pick acoustics over isolation. <

Bryan Pape's wall suggestion is excellent because it gives you the best of both. Whatever you do, don't waste your money on those sheet vinyl products. Sheet rock is the cheapest and most effective mass you can buy.

So build the wall as Bryan described, then treat the inside of the room. For my best advice on that, see the Acoustics FAQ:

www.ethanwiner.com/acoustics.html

It's a lot to read (but read it anyway), and here's the one sentence summary: Bass traps straddling as many corners as you can manage, including the wall-ceiling corners, and mid/high frequency absorbers at the first reflection points on the side walls and ceiling.

--Ethan

[bpape]

I guess I should qualify what I said a little bit as doing doubles on the outside may not be feasible.

The other option is to use RSIC clips and hat channel on the inside (NOT RC).  It allows the drywall to absorb but also provides some good isolation.   It's MUCH more predictable than RC in terms of what it's going to do inside the room.

[Rashiki]

I guess I should qualify what I said a little bit as doing doubles on the outside may not be feasible.

Agreed. I was actually thinking about putting strips of drywall on the inside part of the outer wall. The strips would have to fit between the studs, so I'm not sure that they would be as effective as large pieces. I guess I would have to secure them carefully to get any benefit. I'd rather not build on the inside of the wall because the room is already small enough.

Going back to Ethan's comment about sheet rock beign the cheapest and most effective mass -- I really hate working with the stuff, so I 'm wondering if wood would be as effective. I'm thinking about either sheets of plywood or 1x4 or 1x6 boards. Is wood as effective, or are there other materials that are just as good or better than sheet rock? I have a farily small room, so a 2x or even 3x increase in cost per square foot would still be within my budget.

 -Rob

[ScottMayo]

Going back to Ethan's comment about sheet rock beign the cheapest and most effective mass -- I really hate working with the stuff  ...

Sheetrock is likely to be cheaper and heavier than wood, as well as more fireproof and dimensionally stable and other good things. Use 5/8th thick gypsum, unless someone makes something thicker. And mud is good. More mud is better.

3/8th gypsum passes a fair amount of low frequency sound - so it's possible to make a sort of basstrap out of your walls, by having a thick layer of gypsum outside, some air space, some insulation, and then the thin gypsum on the inside. It's not a complete solution to bass control, but it helps some, and it also provides good attenuation.

Keep in mind that any hole you put in the gypsum - light switches, heating pipes, wiring - amounts to a highway for sound. You'll be amazed at how much leaks out, if you don't design to minimise holes. Air conditioning ducts are nightmares. Use sillicone caulk by the handful to seal up holes and gaps, and to keep wall materials "floating" as much as possible.

The moral is soft, heavy, squishy. That's what stops sound.

[bpape]

1/2" and 5/8" also make good bass absorbers from walls that are insulated - though at different frequency ranges.

Even double drywall will act as a bass absorber.

It's not so much what it passes as what it's mass is coupled with the depth of the cavity and amount of insulation inside the cavity that determine the frequency range of absorbtion and the width of same.

From a purely soundproofing standpoint, it's tough to beat layers of drywall for the buck.

[JLM]

My new listening room (Cardas proportioned 8 ft x 13 ft x 21 ft) has drywall on insulated staggered double stud walls, so the only sound transmission is via top and bottom plates.  Also using insulated flexible duct for supply and return ventilation (that won't vibrate or transmit sounds like sheet metal ductwork).  The room will also have a weather sealed insulated exterior door and sits on a concrete basement slab.  Electrically I have three dedicated 20 amp circuits running to single Hubbell hospital grade 20 amp cryo'd duplex convenience receptacles that are dedicated to audio (and I'm running battery powered amp and DAC).

Unfortunately the contractor refused to hang the ceiling drywall from metal furring strips, so its directly screwed to the wooden floor trusses above.  I did not have the dedicated circuits wired to the top of the panel as some suggest.  The house is a new build with underground service and its own transformer.

When done initially the extra cost was minimal (door = $50, insulation = $40, additional studs = $90, ductwork = $0, wiring/receptacles = $90).

[lcrim]

Because I own a townhouse and share a wall in one of my listening rooms I faced the soundproofing issue and talked about it on this forum.  
What I ended up doing was having a contractor cover the wall with a composite material that was a fibrous material that was absorptive and had fire retardant properties, I believe it was called Quiet board .  Then a metal channel was run lengthwise and another layer of 5/8 sheetrock was screwed to the metal channel.  The edges were sealed w/ an acoustic caulking compound.  In essence the wall floats and transmission of noise from my space to my neighbor's space is drastically reduced.  
Unfortunately I would need to do the same thing on my neighbor's side to prevent hearing her noise but I can always put on some music.