Adhesive/materials for Constrained Layer Damping

[Paul W]

Need some input on constrained layer damping for a 9'x20' (wall sized) panel...

There are at least two different approaches, one here:
Multi-layer damping
This seems to be similar to the roofing felt approach often mentioned but, since very high sheer strength may be important, what is the best adhesive to use with constrained layer(s) of roofing felt? Contact cement?

and another approach here:
Single component - Green Glue
Easier to implement, but is performance compromised?

For frequencies below 100Hz, which option provides better damping and isolation?

What other alternatives should be considered?

[MaVo]

I second that question, i would really like to learn more about this, as i have been told about this subject by gedlee in another thread. Also, thanks for the links.

[legris00]

I am in the process (testing at the moment) of building some monitors out of steel.
Have used a layer of rubber inside (see pic, only shows when was being fitted). Seems to be working, not sure if used with something else than steel...

Any thoughts or comments?

[c2cthomas]

Paul - you might find this useful - maybe - got $$$$ ?
http://www.soundproofing.org/infopag...FVB1OAodbly3ug

Here is another line to some adhesive http://www.quietsolution.com/html/quietglue.html

and Soundproof wood (along with some articles and tips to read.) http://www.quietsolution.com/html/quietwood.html

Soundproofing drywall - http://www.quietsolution.com/html/quietrock.html

and some information for CLD - Constrained Layer Damping
http://www.audioholics.com/education...-speakers-pt-2

I haven't had a chance to try any of these materials so I can't vouch for them. I did see a submarine that had like about 6 inches of rubber (I'm guessing) coating it's hull - and that was supposed to quiet things down real well!



BTW - almost forgot --- Neoprene rubber - either solid sheets or glued together layers can work well. Grab some old truck or tractor tire inner tubes - cut to fit - glue as required - should work. You can buy the stuff on xbay but it's so darn heavy that the shipping cost will kill ya.

[khush]

Hi Paul,

I have used green glue for a few small scale projects (speaker related)
and feel pretty confident that it is an effective damping solution.
Roofing felt and other materials are often mentioned as constrained layer damping materials but has anyone ever measured their effectiveness?
Green Glue has had plenty of independent tests done to back up their claims. Probably it's main attraction for sound isolation is that it is effective at damping the main resonances of sheet rock walls thereby increasing sound insulation at <100hz.
However it ain't cheap 180 sq ft would take 18 tubes, a couple of hundred bucks.
What is this panel, and what are you trying to achieve?
If it is for sound insulation It would be useful to have a good look around the greenglue site or some of the home studio building sites and forums. sub 100hz sound isolation doesn't come easy and getting small details right is essential.
good luck
Khush
http://forum.studiotips.com/viewforum.php?f=1
http://www.johnlsayers.com/phpBB2/index.php

[sreten]

Originally posted by Paul W

Need some input on constrained layer damping for a 9'x20' (wall sized) panel...

For frequencies below 100Hz, which option provides better damping and isolation?

What other alternatives should be considered?

Hi,

It is not obvious at all what you are trying to do. If you want acoustic
absorbtion or acoustic isolation are two entirely different matters.

At frequencies below 100Hz its hard to see the relevance
of constrained (or for that matter restrained) damping.

/sreten.

[MaVo]

Hi sreten, do you mind to explain?

To my small understanding, the CLD walls absorb low frequency energy, so they stop the waves from going through and from reflecting back into the room. That would mean, that absorption of waves in the room and isolation for waves out of the room are both achieved.

[sreten]

Originally posted by MaVo
Hi sreten, do you mind to explain?

To my small understanding, the CLD walls absorb low frequency energy, so they stop the waves from going through and from reflecting back into the room. That would mean, that absorption of waves in the room and isolation for waves out of the room are both achieved.

Hi,

For soundproofing a wall CLD has some advantages but this will barely
affect the acoustics inside the room. If anything for example damping
a drywall that has absorption in the bass will reduce this absorption.

However what does a 9' x 20' panel actually mean ? free standing ?
on a wall ? what type of wall etc. and what is it wanted to do ?
affect room acoustics ? provide soundproofing ?

/sreten.

[Paul W]

More info... The project is a wall sized baffle for sealed subwoofers, with sub-enclosures for LCR main speakers. The objective is to help reduce stored energy radiated into the room to an absolute minimum.

Building the baffle to be very stiff is no problem as extensive bracing will be implemented, including bracing directly to a solid concrete back wall. The current plan is to build the subwoofer portion of the baffle without damping, but make it stiff enough to ensure baffle resonances are well above the subwoofer range. The LCR sub-enclosures are more likely candidates for CLD, but I thought the subwoofer portion of the baffle should be considered while in the planning phase.

The main subwoofer baffle will likely be used for at least 10 years, so I want to build it correctly, and build it only once .

The test phase will be short so I want to limit sample testing to those most likely to succeed...which is why I need to know the proper adhesive for the roofing felt approach.
Thanks,
Paul

[sreten]

Hi,

I still not sure what you have got in mind - how far from the rear wall ?

/sreten.