Does impedance mismatching apply to multiple layers of drywall?

BCNinternational · 10th July 2008, 07:41 PM

Dear Friends,

Will varying the thickness of subsequent layers of drywall benefit a wall system in a similar manner to mismatching the size of each pane of glass in a double glass window construction?

SYSTEM #1
Floor-to-Ceiling 2x6 stud frame with 5/8" drywall (1st layer) then 1/2" drywall (2nd layer) or vice versa (any reason one way is better?)

SYSTEM #2
Floor-to-Ceiling 2x6 stud frame with 5/8" drywall (1st layer) then 5/8" drywall (2nd layer)

Which is the superior wall system when ISOLATION is the primary concern?
I assume #2 but want to know your thoughts.

Thanks!

lakeshorephatty · 10th July 2008, 07:44 PM

The two choices have positives and negatives to them but the mismatched will be better over a broader range i think. Don't quote me, instead go here for all your acoustics and building questions:

John Sayers Productions find the forum on that site. its gold.

Ethan Winer · 10th July 2008, 09:59 PM

If by "layers" you mean the two pieces of drywall are adjacent and touching and screwed together etc, I believe all that matters is the total thickness. And of course thicker is always better. This is not the same as two panes of glass, because in that case there's a space between the panes.

--Ethan

avare · 10th July 2008, 10:22 PM

There is no simple answer to a simplistic question. With studio isolation, the biggest problem is low frequency isolation. When two layers of a leaf are made of the same material and thickness, the coincidence frequency where isolation reduces is the same so the reduction at that frequency is greater. However this is at such a high frequency that the advantages of greater low frequency isolation are greater than the loss at high frequencies.

With all the above taken into consideration, SYSTEM #2 is better for studio isolation.

Andre

divingduck · 11th July 2008, 12:13 AM

And don't forget Green Glue between the layers.... pricey, but the reports seem to be good. (what does Ethan think?).

[I don't sell it. I'm buying a load for my room, so I want it to work!]

BCNinternational · 11th July 2008, 03:31 AM

lakeshorephatty - true; John Sayers forum

Ethan Winer - your opinion and input are always appreciated

Avare - informative and to the point; your input has greatly influenced my project twice now

DivingDuck - I am mid build so it is too late for green glue, good luck with your build.

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10th July 2008, 09:59 PM	#3
Ethan Winer Lives for gear Join Date: Oct 2002 Location: New Milford, CT, USA Posts: 4,834	If by "layers" you mean the two pieces of drywall are adjacent and touching and screwed together etc, I believe all that matters is the total thickness. And of course thicker is always better. This is not the same as two panes of glass, because in that case there's a space between the panes. --Ethan __________________ www.realtraps.com The acoustic treatment experts ----------------------- Amazing Telecaster guitar video

11th July 2008, 03:31 AM	#6
BCNinternational Gear nut Join Date: Sep 2007 Location: Virginia, USA Posts: 75	Thanks! lakeshorephatty - true; John Sayers forum Ethan Winer - your opinion and input are always appreciated Avare - informative and to the point; your input has greatly influenced my project twice now DivingDuck - I am mid build so it is too late for green glue, good luck with your build. __________________ Respect and God Bless, Dan BCNiSS

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10th July 2008, 07:41 PM	#1
BCNinternational Gear nut Join Date: Sep 2007 Location: Virginia, USA Posts: 75	Does impedance mismatching apply to multiple layers of drywall? Dear Friends, Will varying the thickness of subsequent layers of drywall benefit a wall system in a similar manner to mismatching the size of each pane of glass in a double glass window construction? SYSTEM #1 Floor-to-Ceiling 2x6 stud frame with 5/8" drywall (1st layer) then 1/2" drywall (2nd layer) or vice versa (any reason one way is better?) SYSTEM #2 Floor-to-Ceiling 2x6 stud frame with 5/8" drywall (1st layer) then 5/8" drywall (2nd layer) Which is the superior wall system when ISOLATION is the primary concern? I assume #2 but want to know your thoughts. Thanks! __________________ Respect and God Bless, Dan BCNiSS

10th July 2008, 07:44 PM	#2
lakeshorephatty Gear addict Join Date: Dec 2005 Posts: 308	The two choices have positives and negatives to them but the mismatched will be better over a broader range i think. Don't quote me, instead go here for all your acoustics and building questions: John Sayers Productions find the forum on that site. its gold.

10th July 2008, 10:22 PM	#4
avare Lives for gear Join Date: May 2004 Location: Hamilton, On Canada Posts: 948	There is no simple answer to a simplistic question. With studio isolation, the biggest problem is low frequency isolation. When two layers of a leaf are made of the same material and thickness, the coincidence frequency where isolation reduces is the same so the reduction at that frequency is greater. However this is at such a high frequency that the advantages of greater low frequency isolation are greater than the loss at high frequencies. With all the above taken into consideration, SYSTEM #2 is better for studio isolation. Andre

11th July 2008, 12:13 AM	#5
divingduck Gear nut Join Date: Jun 2006 Location: London Posts: 100	And don't forget Green Glue between the layers.... pricey, but the reports seem to be good. (what does Ethan think?). [I don't sell it. I'm buying a load for my room, so I want it to work!]