Author Topic: Floor Joist Cavity Sound Dampening Suggestions  (Read 16222 times)

Randy S

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #15 on: January 06, 2012, 12:52:57 AM »
well thats not to bad considering the materials and cost...Good job...
I would add up the cost of the styro foam and sound board and see if it came out more than MLV or a second layer of 5/8" sheetrock...just curious.
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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #16 on: January 06, 2012, 02:28:21 AM »
Way less than the MLV prices I've seen and for that matter also Greenglue and Resilient Channel but drywall's cheap and so was the styrofoam and soundboard. I can always add another layer of SB and DW for about $60 though. I may change up the configuration a bit in the master bedroom or just add a few more alternating layers of the soundboard and drywall also since it is the noisier of the two rooms.

I don't think the flanking noise is too much of a factor but that is part of what I am evaluating first before and if I proceed any further in second room.

I'll keep you posted.


Randy S

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #17 on: January 06, 2012, 04:01:10 PM »
Stick with double layer drywall, drywall is a better STC than sound board and if the cavity is filled with insulation you dont need double absorption layers...more mass=more blocking. ;)

Randy Sieg

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #18 on: January 07, 2012, 12:10:25 AM »
Prior to doing any work as a test I place a piece of drywall on the existing wall the put my ear to it and it basically sounded about the same as the original wall. Then a piece of styrofoam and then the drywall on top of that which produced a more noticable difference. It may only matter if you have your ear directly on the wall but seems like the vibrations are going to be more easily transmitted through the same type materials. My thinking is the styrofoam or soundboard are light and soft so that would help break the connection so to speak.

Also I drilled what I would call relief holes (about half dozen 3/8" size) in the ceiling drywall between the existing drywall and the new finish layer of drywall to insure that the wall wasn't completely airtight since both layers of drywall are sealed and not wanting it to act like a speaker box in a way.

All speculation on my part though ... ;D



Randy S

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #19 on: January 07, 2012, 04:09:20 PM »
hmm, you want air tight to achieve maximum reduction...I can see a value change with the sandwich (drywall/foam/drywall)..

well what I can say is, no matter what you do it will make changes in reduction. Some of the best cost effective systems have come from"out of the box" thinking....and using standard building materials have performed nicely when used in the right order.
It is very difficult to determine diminishing factors this way because the changes are not dramatic.
So, since your getting continuous reduction than you are doing it right.
Keep me posted on the noise reduction value as you proceed, it will be nice to know what total value you achieve.
 
Randy Sieg

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #20 on: January 07, 2012, 09:49:52 PM »
I knew that it was suppose to be airtight but I got it in my head in this configuration that the small amount of air could be more of a factor than a larger air cavity. The best improvements were with the tv, microwave oven, cupboards and the ac unit (which is literally less than 15' and level with that room). TV and microwave are for the most part inaudible now. The cupboard noise is not as intrusive and is exceptable as is the ac unit also now. Voices are in the good range but could be better, dog barking could use improvement for sure but is ok but still not to the level I would prefer.

What I am trying to determine is if the added layers would be of benefit or if it is flanking noise. I may have to install another layer to find out and I can always take it down and use it in the master bedroom if it has no affect.

I will keep you posted.

 

ArminRU

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #21 on: January 08, 2012, 12:10:42 AM »
Our view points on insulation:

1) cotton fiber insulation (recycled blue jeans)
2) mineral wool

better than nothing in the cavity

3)fiberglass
4) blown in

And tst me, I have had clients see a value of noise reduction in all the types of insulation it really comes down to how much vs. cost.

Randy, do you have any stats to back up your ranking?  I've always heard that R19 pink fiberglass insulation is just as good as mineral wool and anything else.  Do you have first hand experience comparing the same wall setups and just different insulation?

Randy S

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #22 on: January 09, 2012, 11:03:12 PM »
you can always review the NRC data provided by the manufacturers,
just remember that field results and lab testing is  different end results.
Ex: cotton fiber has a NRC of 1.15 and an astm e90 test result of 57 for R19.
However, in the field you should only use the value of .95 max and true STC rating would be determined by assembly being decoupled or coupled.
The statement I made in my post is purely off of a field evaluation in noise reduction.
Feel free to contact me directly if you would like to discuss real world reductions based on materials vs. assembly.
Randy Sieg

Super Soundproofing Co
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888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #23 on: January 22, 2012, 06:43:11 AM »
Have been looking at the test result charts at the Greenglue site, I was interested in the soundboard and drywall results which are not being compared with each other on the same chart but was easy enough to print and combine the two into one. Interestingly enough the soundboard and drywall have very similar results except in the 800-2500 Hz the soundboard actually out performs the drywall up to about 5 dBs as far as sound isolation. Anyway I think my original configuration of existing drywall /styrofoam/soundboard/styrofoam/drywall is probably a good way to go in the Masterbedroom also when I get to it.

Nothing much more to add other than I feel for the same money as I spent in the small bathroom using the Greenglue I was able to do the bedroom for and the results were much more impressive in the bedroom.

Probably be awhile before I do anything else but will post then.

Randy S

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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #24 on: January 23, 2012, 01:45:38 AM »
so based on what you have learned would you say the value of vibration absorption in a material with in contact to the studs, including the amount of hard connections are what actually delivered your sound reduction value?
In the end, what you are seeing as the primary value is decoupling....break or reduce the amount of hard surface or direct connection to the surface that is vibrating...
also as a side note..the frequency you mention happens to be human speech frequency which is the best data across most test specimens..
wave length  1/4" to 1/2" max...(frequency / 1129 fps.)= wave length.
..

it is a pleasure having your input and feed back!
Thank You Condo...Keep it coming my friend.

Randy Sieg

Super Soundproofing Co
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888-942-7723
Ph. 760-752-3030
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Re: Floor Joist Cavity Sound Dampening Seggestions
« Reply #25 on: January 23, 2012, 04:57:04 AM »
That is a good question and it's hard for me to say which one is most responsible for the sound reduction. The materials all conduct sound by themselves when I use a small sample on the wall to test but I would say the styrofoam is the poorest sound conducter then the soundboard with the drywall seemingly to produce the clearest sound of the bunch. As far as using different combinations of the materials the best test results are ones that include the styrofoam so I do feel some decoupling affect is being achieved by it's use though hard connections have to play some role in the final results, also if I stack drywall on soundboard as a test the improvement is only a little better than each by itself. Pretty primitive method so take it with a grain of salt. The master bedroom will be a better indication of the materials effectiveness though so we will see.

Thanks for the side note I'll probably double the soundboard in the Master Bedroom for that reason.

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Re: Floor Joist Cavity Sound Dampening Suggestions
« Reply #26 on: March 09, 2012, 11:09:23 PM »
Haven't got to the Master Bedroom yet because I wanted to be sure I had done all that I could in the other room before proceeding and after some time I feel the flankinging noise is louder that the wall I worked on so it wouldn't make sense to do more in that particular room. Textured today will paint and finish up this weekend probably ...

2-1/4" was all I lost in that room but I most likely will double that in the master since it is much louder in that room still not bad for the cost comparitively ...