effect of the extra absorber layer - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 8 Old 12-02-2011, 08:07 AM - Thread Starter
Member
 
manusha's Avatar
 
Join Date: Mar 2011
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 10
What kind of sound attenuation improvement at low/mid/high frequency ranges can be expected when adding a 2"-3" thick absorber material such as owens 703 or roxul safe 'n' sound in between two 4" thick brick walls separated by a 6" air gap? (so the final air gap reduces to 4"-3" after adding the absorber layer).
manusha is offline  
Sponsored Links
Advertisement
 
post #2 of 8 Old 12-02-2011, 08:56 AM
AVS Special Member
 
stockmonkey2000's Avatar
 
Join Date: Nov 2005
Location: Utah County
Posts: 1,710
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 25
OC 703 would be a waste of money in that application. Use that on the inside of the room for acoustic panels. Cheap fluffy insulation is generally recommended. The safe and sound is not that expensive but more than fluffy fiberglass and you would not notice any difference. Here is a chart showing the STC of various materials. Double brick is not shown so I'm not sure how well the entire assembly would do.

http://www.sae.edu/reference_materia...TC%20Chart.htm
stockmonkey2000 is offline  
post #3 of 8 Old 12-02-2011, 09:12 AM
AVS Special Member
 
Ted White's Avatar
 
Join Date: May 1999
Location: Michigan, USA
Posts: 8,187
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 35
Exactly. Just throw some R13 in there. The insulation will not make a big deal in any event.

__________________

Ted



The Soundproofing Company
Ted White is offline  
post #4 of 8 Old 12-17-2011, 08:18 AM - Thread Starter
Member
 
manusha's Avatar
 
Join Date: Mar 2011
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 10
Is it possible to get similar insulation if i reduce the air gap to 2" and fill it with 2" 703?
manusha is offline  
post #5 of 8 Old 12-17-2011, 08:57 AM
AVS Special Member
 
Ted White's Avatar
 
Join Date: May 1999
Location: Michigan, USA
Posts: 8,187
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 35
No. The air volume is a factor in the calculation of the resonance point of the partition. Reducing the air volume will raise the resonance frequency of the wall, and in any event 703 is too dense.

We want the resonance point as low as possible in the walls and ceiling. The lower it is, the lower the frequencies we're isolating. That's an admittedly broad statement, but a good rule of thumb.

Assuming the system is decoupled, the two factors that define the resonance point is the mas and the air cavity volume. Mass is a much bigger driver, so a smaller air cavity is more than offset by an increase in the mass.

The foundation wall, due to the mass of the foundation, will tend to define a pretty low resonance point, so if you were needing closer clearance on the foundation walls, I'd consider using clips and channels and attach to wood furring secured to the foundation.

__________________

Ted



The Soundproofing Company
Ted White is offline  
post #6 of 8 Old 12-19-2011, 10:12 PM - Thread Starter
Member
 
manusha's Avatar
 
Join Date: Mar 2011
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 10
Little bit of clarification..

This is what i understood from your post.

The contribution from mass is a much bigger driver for resonance frequency. In that case, if i reduce the air gap to 2" and do not fill anything inside, the resonance frequency (and hence the sound insulation) will not change much. Any small change can be offset by using clips and channels attached to wood furring rather than filling 703.

Is that what your are suggesting?

Thanks
manusha is offline  
post #7 of 8 Old 12-20-2011, 06:41 AM
AVS Special Member
 
Ted White's Avatar
 
Join Date: May 1999
Location: Michigan, USA
Posts: 8,187
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 35
A reduction or increase in cavity volume will reduce or increase the resonance frequency of the wall. Big drum vs. little drum sort of thing.

A reduction or increase in mass on the decoupled framing will reduce or increase the resonance frequency of the wall also.

Of the two, the mass will have a bigger effect on the ultimate frequency.

Any hollow cavity will require insulation to deal with cavity resonance.

703 is too dense to use in walls / ceiling.

__________________

Ted



The Soundproofing Company
Ted White is offline  
post #8 of 8 Old 01-07-2012, 06:59 AM - Thread Starter
Member
 
manusha's Avatar
 
Join Date: Mar 2011
Posts: 18
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 10
Later realized that having a 6" space would not be practical as it will reduce the room space quite a lot. However i still need a pretty good isolation. My plan is to reduce the fap to 3" and put Roxul's Safe'n'Sound 2" between the walls which will result in a 1" air gap. Appreciate if some one can help me in finding sound attenuation at low frequencies for such a setup.
manusha is offline  
Reply Dedicated Theater Design & Construction

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off