Trying to come up with a solution for interior soundproofing. I can use batts that are soundproof-rated, or drywall, specifically Quiet-Rock. Anyone used Quiet-Rock? Any cost analysis batts vs. drywall?

Jcampagna:

My understanding of Quite Rock or Quiet Zone drywall is that it's just ordinary drywall with a thin sheet of lead metal inside it. That lead is intended to simply make the drywall heavier. You can accomplish exactly the same result by using two layers of drywall instead of one. Increasing the mass of a wall is highly effective in increasing that walls ability to stop noise.

If you're talking about "batts" as batts of insulation installed in the stud spaces of an ordinary stud wall, then you're following a misconception that batts of insulation in the stud spaces help deaden sound.


Sound passes through a wall by causing the wall to move in response to the changing air pressure caused by the sound wave. The movement of the wall, in turn, creates a new sound wave on the opposite side of the wall. Since the insulation in the stud spaces play no part in that process, it really doesn't matter if you have insulation in the stud spaces or not.

You'd be much better off building two parallel walls and putting two layers of drywall on one side of each wall. Also, stick the two layers of drywall on each wall together with some thing called Green Glue.

Green Glue is a glue that never actually dries solid. It remains a viscous liquid so that it has to distort in shape whenever one sheet of drywall moves relative to the other. The result is that it absorbs energy, thereby reducing the movement of the drywall.

Google the following character strings:

noise transmission through building components Quirt

Green Glue

With the first one, you will get a research paper published by a guy named Quirt who was working for the Canadian National Research Council at the time. The result of his findings was that the two most effective methods of reducing noise transmission through buildings was by either physically uncoupling walls from their supporting structures or by increasing the mass of walls significantly (by, for example, replacing drywall walls with brick walls).

The second character string will give you the company that makes a product you can apply between two sheets of drywall that will absorb energy when the two sheets move with respect to each other.

Also, keep in mind that our hearing isn't linear. We hear quiet sounds much better than we hear loud sounds. So, even if you reduce the sound pressure level by 90 percent, the "apparant" reduction will be closer to 50% because we hear that quieter noise much better than we hear louder noises.

This message has been edited. Last edited by: Nestor,

Also, go to the Windows, Walls and Doors forum and read my post in the thread entitled "Bedroom Door, Sound".

If you just Google sound proofing there's lots of better info and design ideas there.

quote:

Originally posted by joecaption:
If you just Google sound proofing there's lots of better info and design ideas there.

Joe, it looks very unprofessional for the supposed experts in here to be disrespecting each other's responses to questions. If you have better advice to offer, then share it with the poster.

To say: "Go look it up on the internet" is as good as no answer at all. I'm sure the OP would be aware that he/she can do that, but is wanting to avoid having to spend the time learning enough about the topic to decide on a solution themselves.

Nestor is a very helpful contributor to these boards, but there are some misconceptions in his post. I have learned that he knows much more than me when it comes to DIY and home improvement. However, I am a professional acoustical consultant, so I win the experience prize in this discussion.

quote:

Originally posted by Nestor:
My understanding of Quite Rock or Quiet Zone drywall is that it's just ordinary drywall with a thin sheet of lead metal inside it. That lead is intended to simply make the drywall heavier. You can accomplish exactly the same result by using two layers of drywall instead of one. Increasing the mass of a wall is highly effective in increasing that walls ability to stop noise.

It's true that increasing the mass of a wall is the best way to improve its ability to stop noise. No argument there.

I believe only older versions (or the first version) of QuietRock had metal in the material. This material required saw-cutting (i.e. it could not be scored and snapped like regular drywall). This caused a significant backlash in the construction industry. As a result, modern versions of QuietRock come with viscoelastic polymers as an internal layer. QuietRock with this construction can be scored and snapped. The viscoelastic polymers do not add significant mass to the gypsum board; instead, they act as a constrained layer damper and reduce the board's ability to vibrate sympathetically when presented with incident sound.

quote:

If you're talking about "batts" as batts of insulation installed in the stud spaces of an ordinary stud wall, then you're following a misconception that batts of insulation in the stud spaces help deaden sound.


Sound passes through a wall by causing the wall to move in response to the changing air pressure caused by the sound wave. The movement of the wall, in turn, creates a new sound wave on the opposite side of the wall. Since the insulation in the stud spaces play no part in that process, it really doesn't matter if you have insulation in the stud spaces or not.

Completely disagree. First, if you look at acoustical laboratory test reports of walls that are built identically with the exception of batts or no batts, the difference in the STC (sound transmission class) rating is about 3-4 dB on average. Lightweight wall construction (i.e. gypsum on studs) isolates sound better when batts are used in stud cavities - that's a scientific fact. That's not to say that STC is the only metric upon which you should be evaluating your wall's sound-isolating performance, but it is a single-number rating that is a good place to start.

Nestor's description of how sound gets through a wall is only partially accurate. Incident sound sets the gypsum layer on one side of the wall in motion, which in turn sets the studs in motion, which is turn sets the gypsum layer on the other side in motion. But this only describes what happens when the sound is in line with a stud. For the remaining 14.5 inches out of every 16 (i.e. the stud cavity), sound either travels through an empty void (if there are no batts) or through insulation of some sort (if there are batts). The sound in the stud cavity will reflect multiple times off of the internal (stud) sides of the gypsum board. Having insulation in the cavities allows this sound to be absorbed, so each reflection is markedly reduced in sound amplitude, not just minimally.

quote:

Also, keep in mind that our hearing isn't linear. We hear quiet sounds much better than we hear loud sounds. So, even if you reduce the sound pressure level by 90 percent, the "apparant" reduction will be closer to 50% because we hear that quieter noise much better than we hear louder noises.

I'm not sure where you've gotten that information, but it simply isn't true.

No disrespect intended to anyone in this thread, but the internet is full of misconceptions about "sound proofing" (this thread really isn't that bad...). There's really no such thing as sound-proof construction, anyway; all sound isolation is a matter of degree, and there will always be a sound source loud enough that it can't be isolated to inaudibility if the source is placed on one side of the wall and the listener is placed on the other side.

This message has been edited. Last edited by: JKeefe,

used to be a recording engineer (yeah, voice radio, so shoot me) and read the literature generally availiable. I am not a certified acoustic engineer.

however... short of pouring sand in the wall cavities (which requires concrete walls) and pouring 3 foot concrete structures (as one wack did to build a subwoofer in their store), the keys are isolation, decoupling, and attention to detail.

isolation: break the material barrier between the sound source and the quiet zone. making 2x4 walls with a 2x6 cavity between them, with no part of wall A touching wall B, and then filling the cavities with a dampening insulation like rockwool batts is a fine start. acoustic drywall provides some through-material isolation because of its higher density, aka weight, to sound. IIRC they have tried making acoustic drywall with air bubbles in the gypsum, not special.

decoupling: sort of overlaps with isolation, but there are materials such as perforated wave-formed steel panels, soundproof/fireproof acoustic foam, and multipane windows with each glass pane mounted at a different angle in rubber that provide additional isolation from a sound source. most of these are not specific to all frequencies, but have tone (octave) ranges in which they are quite effective. classic RCA live testing in front of an audience with an orchestra to determine whether full-range sound or distorted sound was done in the 30s to determine why audiences hated some electronic products. the modifications were made by rotating in groups of perforated steel panels which selectively dropped out octave ranges of sound.

attention to detail: the ONE stud common to both walls is going to become like a speaker. the gap in batt insulation is going to be an echo chamber. sloppy work can negate everything you've tried.

This message has been edited. Last edited by: swschrad,