Acoustic Drywall Sound Absorption vs. Transmission

Robert · Apr 1, 2016

Hi,

Any dry wall products or installation techniques to reduce sound reflections?

I have a detached home, so sound transmission is not an issue.

It would seem that the material in front and behind the drywall would have the greatest effect because of their thickness.

But what about using isolation channels with resilient sound clips to decouple the panels from the studs. Would that have much impact on reducing reflections?

Thank you

Steve Williams · Apr 1, 2016

Robert said:
Hi,

Any dry wall products or installation techniques to reduce sound reflections?

I have a detached home, so sound transmission is not an issue.

It would seem that the material in front and behind the drywall would have the greatest effect because of their thickness.

But what about using isolation channels with resilient sound clips to decouple the panels from the studs. Would that have much impact on reducing reflections?

Thank you

I did a double layer wherein I used Quiet Rock glued and screwed onto the underlying drywall. I also used a special calking that decoupled the corners

Bruce B · Apr 1, 2016

Robert said:
Hi,

Any dry wall products or installation techniques to reduce sound reflections?

I have a detached home, so sound transmission is not an issue.

It would seem that the material in front and behind the drywall would have the greatest effect because of their thickness.

But what about using isolation channels with resilient sound clips to decouple the panels from the studs. Would that have much impact on reducing reflections?

Thank you

Nothing is going to stop reflections off bare drywall. You need something on top of the drywall to do that. I used Snap-tex, which is 1-2" 703 rigid fiberglass with Guilford of Maine fabric covering. Another thing you can use is products from ASC, Kinetics Noise Control and others (whose names escape me now)

Using resilient channel and double layer drywall helps in decoupling and sound resistance from outside sound and sound leaving the room.

I used dRC from ASC (http://www.asc-soundproof.com/iso-wall/system-diagrams/), then used double layer drywall with Green Glue inbetween. The second layer of drywall is at a 90 degree angle with overlapping seams.
The corners and junctions were filled with acoustical caulking. You want a caulking that never hardens.

Steve Williams · Apr 1, 2016

You want a caulking that never hardens.

That's what I used

LenWhite · Apr 1, 2016

Robert said:
Hi,

Any dry wall products or installation techniques to reduce sound reflections?

I have a detached home, so sound transmission is not an issue.

It would seem that the material in front and behind the drywall would have the greatest effect because of their thickness.

But what about using isolation channels with resilient sound clips to decouple the panels from the studs. Would that have much impact on reducing reflections?

Thank you

Acoustic Frontiers (Nyal Mellor) designed my medium sized room acoustics and provided optimum inside wall dimensions. The finished room dimensions are 19'-6"L x 15'-3"W x 11'H.
The media room acoustic "foundation" consists of an isolated wall system comprised of 130 Kinetics IsoMax clips attached to 1-1/2" furring strips nailed to CBS blocks on all four walls. 440 linear feet of 25mm hat channel is supported by the isolation clips. R-11 open faced fiberglass (3-1/2" thickness) fills the empty areas between the CBS walls and drywall. Soundboard XP damped drywall is attached to the hat channel. Acoustic sealant seals the areas between the top, bottom, corner areas of the damped drywall. The ceiling utilizes Soundboard XP attached to the ceiling joists. The media room attic has R-38 fiberglass insulation. A knee-wall with attached R30 fiberglass insulation separates the media room attic and the original structure interior attic area.

Acoustic Frontiers also incorporated my existing Rives Audio ceiling RPG BAD panel "clouds" and using room dimensions and frequency measurements specified the interior walls RPG modex plates, RPG BAD panels, and Listen Audio diffusers. The acoustic design creates a flatter frequency response; lowers the room reverberation time; and provides bass trapping. Clarity, soundstaging, and imaging are all improved while keeping the room as live as possible.
Nyal Mellor says if you build the room from scratch you can use the structure (walls, ceiling) as a bass trap. That's what he did in my room.

If you would like to see pictures and a more detailed description of my room look here https://systems.audiogon.com/systems/5013

Steve Williams · Apr 1, 2016

Nyal Mellor says if you build the room from scratch you can use the structure (walls, ceiling) as a bass trap. That's what he did in my room.

I agree Len

My walls and floors behave as bass traps

rockitman · Apr 1, 2016

Great looking room you have there Len.

treitz3 · Apr 1, 2016

I will ditto what Christian said. Extremely well executed!

Hello Robert, have you given any thought to bull nosing the corners of the room?

Tom

Rodney Gold · Apr 1, 2016

I used slotted and pierced wood paneling , on battens with medium density rockwool/uthermo between it and the walls as the entire skin to my room , I can play as loud as I like with minimal sound transmission
its also a sort of diffuser and absorber
Im sure you could get the same in the USA

Here is the stuff that went in the gaps .. bales
My room walls are about 560 sq ft....

Steve Williams · Apr 1, 2016

That is a very interesting technique Rodney

Rodney Gold · Apr 1, 2016

wow , you went to town on that room, over here in SA I'm classed as lunatic fringe cos of my treated room..
well done , hope the sound paid off big time...
Im totally converted as to how important the room is if you want best sq from wot u got...

LenWhite · Apr 1, 2016

rockitman said:
Great looking room you have there Len.

Thank you Christian. I watched your AVShowrooms video for the first time - your audio system and music collection is awesome!

LenWhite · Apr 1, 2016

treitz3 said:
I will ditto what Christian said. Extremely well executed!

Tom

Thanks Tom. A lot of planning and execution went into this room. I use the room almost daily and enjoy listening to music immensely.

rockitman · Apr 1, 2016

LenWhite said:
Thank you Christian. I watched your AVShowrooms video for the first time - your audio system and music collection is awesome!

I just need your room now. Thanks.

amirm · Apr 1, 2016

Robert said:
Hi,

Any dry wall products or installation techniques to reduce sound reflections?

I have a detached home, so sound transmission is not an issue.

It would seem that the material in front and behind the drywall would have the greatest effect because of their thickness.

But what about using isolation channels with resilient sound clips to decouple the panels from the studs. Would that have much impact on reducing reflections?

Thank you

Since you don't need sound isolation, you want the floppies, softest walls you can get. Such walls then will absorb low frequency waves which is very difficult to do otherwise. The massive total surface area of the wall do a good job there. Stay with a single layer of drywall as it will provide the most flex.

Iso channel is for reducing transmitted noise which you don't need. It is also easily screwed up in installation. So you don't need to go there.

As Don correctly noted, above low frequencies the surface of drywall becomes a great reflector. Nothing you put in the wall or behind it will help although you should put some insulation behind the walls so that the cavity does not resonate.

Nyal Mellor · Apr 13, 2016

amirm said:
Since you don't need sound isolation, you want the floppies, softest walls you can get. Such walls then will absorb low frequency waves which is very difficult to do otherwise. The massive total surface area of the wall do a good job there. Stay with a single layer of drywall as it will provide the most flex.

Iso channel is for reducing transmitted noise which you don't need. It is also easily screwed up in installation. So you don't need to go there.

Yes, single layer, but IT MUST BE DAMPED!!! Otherwise it resonates at a few frequencies, ringing on after the excitation has stopped, screwing up your bass.

The hat channel and clips actually makes the wall even floppier, as it reduce the number of anchoring points, and those anchoring points also have compliance. Another technique is using steel studs 24" on center.

JackD201 · Apr 13, 2016

ST not an issue at my place either. My room is a mix. Like Rodney I have walls with labyrinths backed with rock wool. Also a few fiberglass panels likewise built on and attached with velcro to some of teh gypsum. Some walls are gypsum, damped with silicon crosshatching on the back and cavities likewise stuffed with rock wool. Then there are a bunch of tuned resonators of different frequencies and almute columns and clouds. Lastly the rear is handled with diffusors. Like Bruce I use Guilford fabrics to cover the resonators and the rear diffusor for looks and the fact that they are safer because they don't ignite. The required finishing for the diffusors would have cost a bundle so I covered it up instead. Space frame throughout. Old (pre-basement leak) studs were wood. I can't say that I actually picked up on any difference. It was quite a few months between renovation and the system sources changed substantially in the interim making comparisons difficult if not impossible. Final finish on the gypsum walls also to protect it from dents and scratches and to make the transition from wall to resonators seamless is a type of wallpaper that is rubberized and sturdy. I don't think this does anything to the sound.

So far no ringing except for some of the lighting fixtures which do rattle when I'm being stupid. This is not done often but knowing it can bothers me. Any suggestions for SPL immune recessed light mounting guys?

Robert · Apr 13, 2016

Nyal Mellor said:
Yes, single layer, but IT MUST BE DAMPED!!! Otherwise it resonates at a few frequencies, ringing on after the excitation has stopped, screwing up your bass.

The hat channel and clips actually makes the wall even floppier, as it reduce the number of anchoring points, and those anchoring points also have compliance. Another technique is using steel studs 24" on center.

Thanks for the tip. Seems like there are several styles of channels and clips? Any recommendations on gauge and clips? I was looking at http://www.soundproofingcompany.com/soundproofing101/furring-channel-with-resilient-sound-clips/

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