Not sure if this is the right forum ??? 

I need some help with sound insulation / sound control. I’m finishing 2 adjacent bedrooms in my basement, which are separated by closets. The closets are framed in with 2x4’s (16” on center). I’d like to put some sort of sound treatment in, but my budget is limited. I want to limit myself to options that are compatible with the existing 16” o.c. 2x4 walls.

Also, I have lots of ½” drywall, and standard thermal fiberglass insulation batts (anywhere from R-11 to R-15).. so using these materials will have preference for me. I was considering putting double layer of ½” drywall inside the closets and putting some sort of batt insulation between the studs.

When digging some more I came across so many options I became confused. For wall cavities there’s…… std fiberglass batts, special “quiet” fiberglass batts, sheep wool batts, rock wool batts, and even some formed cellulose batts. There’s special adhesive, “green glue” which is very expensive but seems very effective from the testing online and reports from happy customers who used it. And there’s some high tech foam/plastic type sheet roll that is said to be “revolutionary” and yet only 1/8” thick (http://www.acoustiblok.com/).
Questions:

1. Anyone heard of the “acoustiblok” 1/8 inch thick blanket at the link above? Anyone have an idea of much it costs. And how it performs?

2. When comparing standard fiberglass thermal insulation, are the R-15 3.5” batts going to be a better sound barrier/absorber than similar thickness R-11 or R-13 batts ?

3. Do fiberglass batts marketed specifically for sound control perform any different than equal size and weight standard (thermal) fiberglass batts?

4. Are rock wool or mineral wool batts going to make a big difference when compared to just standard fiberglass batts (rockwool batts seem to be about 2.5 time the cost of std fiberglass R13, at least locally here in West Michigan) ?

5. Is the green glue damped adhesive going to make a big difference over standard construction adhesive?

6. If I’m going to do dual layers of ½” drywall in the closets. How do I attach the dry wall layers if I’m going to use “green glue” damping adhesive? How should I best do it if I can’t afford the “green glue” ??

Thanks in advance for any help or advice!

In order:

1: Acoustibloc is not a low-cost solution for the budget minded

2: Higher density R15 fiberglass batts are likely to be WORSE than standard/low density batts, due to it's providing better mechanical coupling between the wallboards.

3:  Most sound-deadening batts for 2x4 construction are nearly the same as R13 unfaced batts (and often labeled with an ASTM C 518 rating for R-value.)

4: Rock wool batts will not make a noticeable difference over fiberglass (except about 3x as itchy. )

5: Green glue WILL make a noticeable difference on double-layered wall board compared to standard construction adhesives.

6: Huh? (Read the instructions, maybe?)

Using metal studs is generally better than wooden studs, staggered studwalls are better decoupled than those where the drywall for each side share a stud, etc.  You can really take this to town if you want to:  http://www.nrc-cnrc.gc.ca/obj/irc/d.../ir693.pdf

Pay attention to any acoustic by passing you might be getting in joist-bay channels between the rooms too.

Dana1 that was a great and thorough reply!

You attach drywall with standard drywall screws. Green Glue is not an adhesive.

Thanks for the info....

I'm going to stick with standard R13 fiberglass cavity insulation and single layer drywall on both sides for now.  Later if sound is really an issue I can add a  second layer of drywall with the super expensive "green glue" with minimal impact to the rooms as I can just apply it on the back wall of adjacent closets that separate the rooms.

Consider using 5/8" drywall for the mass

Also, you might consider installing wood or metal furring channel on the walls, perpendicular to the studs at 24" OC. This isn't decoupling but the 24" spacing rather than 16" will allow for more flex, and greater isolation.

Sound is energy that needs to be absorbed to stop it. I filled the space between 2 drywall walls with loose sand. This made it so you did not hear the sound on the other side of the wall. I sealed the outlets with foam and treated the sand with boric acid just in case.

Brian

Different thickness of drywall can also help.  Different frequencies will react with the mass of the wall slightly differently.  Not a good scientific explanation, but it works.  On one side put 2 layers and 1 on the other.  OR 2 and 3 etc.  The additional mass of the second layer alone will make a difference as well.

 

 

s.kelly that ia a very good point and certainly true. Different panels will have different resonance points so mixing thicknesses breaks up the higher (coincidence) resonance points.

This isn't necessary if you are using a damping compound, since damping compounds directly address resonance. If using a damping compound, forget about differing thicknesses aqnd get as much mass on the wall / ceiling as possible. Generally layers of inexpensive 5/8" drywall will work very well.

I did not realize that the damping compounds made different layers irrelevant.  Good info to know! Thanks

 

 My pleasure

Working in Theatre we deal a lot with sound transmission. The simplest thing is to insulate with standard un-batted fiberglass insulation and double layer the sheet rock. Our sheet rock is vertical and the second is hung horizontal overlapping all the joints. We have a section you can get behind and part of it is single layer sheetrock and it is noticeable how much louder, I would guess the double layer passes 6 to 9 db less. In movie theatres they either use poured concrete or block filled with sand, overkill for a house, unless you’re a drummer

While you can go back and add a second layer, it is a lot easier to do it right away without a lot of cost. The electrical will be right and ½ the plastering and painting. But then again insulating might be enough alone.

Fundamentally if you can incorporate decoupling before drywalling, your isolation will soar. Decoupling refers to staggered studs, double stud walls, resilient clips & channels or even resilient channel (not recommended).

A standard wall is coupled with the drywall on either side sharing the same stud.

I worked on a movie theater a couple years ago.  They dealt with the sound by using  nominal 2x6 metal stud wall with fiberglass batts between.  I think I remember 2 decoupled walls,same construction. On either side they used either 2 or 3 layers of rock.  That was all they did, and it was quiet once the walls were up.

I  am sure another benefit of the several layers of rock was that it also handles fire rating concerns.

Honestly, I think your best bang for the buck would simply be to double-stud.
Sheetrock the "back" of the wall with 5/8".
Layer another layer of 5/8" over the first after Green-Glue'ing the back
Insulate.
Finish the front side with 1/2".

In the other room, add the second stud wall, with the studs offset and a quarter inch air gap.
Insulate that as well.
Finish in 5/8ths.

I agree, in 2x4 stud walls, the sound deadening difference between fiberglass and rockwool is pointless.
I also can't really recommend something like Quietrock (sound deadening drywall) either.
5/8" drywall is $7-8 a sheet in bulk. $9-11 if you get the mold resistant stuff.
1/2" Quietrock is $45-50. And I can't see potentially spending $600-800 on drywall for a single wall when you can spend $200-250 and get nominally the same thing.

I think acoustic insulation roll is one of the best option.

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