[schw06]

I have 2 walls to my listening room that were left without sheetrock on the back side so I could place power outlets and run cables as I see fit. I have that accomplished and I am going to sheetrock the outside of those 2 walls. Is there any significant sonic advantage to put insulation between the studs prior to sheetrock? The other 2 walls do not have insulation. If so, what rating would you recommend. Also, is there any sonic advantage of putting 5/8 inch sheetrock on the outside rather than 3/8's?
David

[bpape]

Absolutely insulate the walls.  The idea is to damp them so they don't ring like big drums.  It also allows them to function as a minimal bass absorber. 

Thicker drywall will provide better isolation as well as lowering the resonant frequency of the wall - hence, lower absorption range.

Bryan

[schw06]

Bryan,
   Thanks for the recommendations. What R rating do you recommend for the insulation?
David
P.S.- I have a room full of GIK panels and absolutely love them(thanks for all your assistance getting them)

[BobRex]

Consider each empty (uninsulated) stud bay as a resonant chamber.  Stuffing the bays will change the resonant frequency and amplitude, and more than likely sound better.  It will also help to isolate the room from the rest of the house.   Another trick would be to install crippler studs / fire blocks in the wall cavity.  That also reduces the size of the chambers and stiffens the wall.  Stagger the blocks so that you don't have uniform sized chambers.

As far as how much insulation,  I'd overstuff the bays.  If you have standard 2x4 walls, use 6 inch (R19) batts (or more if you are willing to splurge.)  The compressed fiberglass will act as a bass trap.

Heavier drywall is also a good idea.  Once again it makes for a stiffer wall, thereby raising the resonant frequency.  In this case, mass is your friend.

Ultimately, while you probaby won't eliminate bass issues, you will reduce their effects.

[bpape]

How much insulation is a point of contention. Once you get beyond the standard R-13, you're actually hurting isolation.  You're also further restricting the ability of the drywall to freely vibrate and therefore absorb bass.  My advice is to just stick to R-13.  Good performance, no isolation loss, less money.

Bryan

[schw06]

Thank you guys for the advice!
David

[Nyal Mellor]

Have a look at the Green Glue website if you get a chance. They have TONS of great educational material. You want the wall to be as good a bass absorber as possible, nice and flexible but well damped. Too solid a wall is a lost opportunity and may cause problems with lack of damping of room modes.

[pslate]

Mineral wool is great if it's in your budget http://www.thermafiber.com/
Small gaps can kill STC values. Avoid the gypsum board that has the gel interlayer. It's cheaper just to double up the gyp board.

USG has great resources
http://www.usg.com/documents/courses/02JuneUnderstandingAcoustics.pdf
http://www.usg.com/sheetrock-acoustical-sealant.html

[geezer]

How much insulation is a point of contention. Once you get beyond the standard R-13, you're actually hurting isolation.  You're also further restricting the ability of the drywall to freely vibrate and therefore absorb bass.  My advice is to just stick to R-13.  Good performance, no isolation loss, less money.

Bryan

That's true for thermal resistance, but for audio purposes, the more the merrier.

[JLM]

STC = sound transmission coefficient (measured in decibels of sound reduction).  You should be able to google/bing to find the STC of different "wall assembles" (description of the entire wall - for instance studs, insulation, drywall, finishes).

Yes two factors, insulation (lack of sound transmission in and out) and sound attenuation (echo/resonance).  One of best/easiest stud wall designs to reduce sound transmission is to use staggered stud wall designs (for instance 2x6 top/bottom plates with two sets of 2x4 studs that are flush mounted to each edge of the plates and staggered from each other).  The cavity is loose insulated (batts or blown).  In this way there is no solid connection between inside and out (except for the plates).

Varying the stud spacing, going with 5/8 inch drywall, and/or using 2x6 studs are other ways to improve the sound attenuation.  As geezer mentioned overstuffing is good for attenuation, bad for transmission.

[AUDFILE74]

Have a look at the Green Glue website if you get a chance. They have TONS of great educational material. You want the wall to be as good a bass absorber as possible, nice and flexible but well damped. Too solid a wall is a lost opportunity and may cause problems with lack of damping of room modes.

http://www.greengluecompany.com/technicallibrary.php

http://www.greengluecompany.com/

[jimdgoulding]

Excellent responses.  Glad to be keeping your company .