Soundproofing expectations below 80hz - AVS Forum
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post #1 of 21 Old 08-20-2014, 06:45 AM - Thread Starter
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Soundproofing expectations below 80hz

Hello all ... I am in the process of framing out a theater room in the basement.

Room is currently about 15'6" x 22'. Current height of the room is 92 inches (distance between concrete floor and framed ceiling).

Distance between the basement framed ceiling and the sub-flooring for the floor above is about 2 1/2 feet.

I was planning to do furring channel, clips, Green Glue, and double 5/8 drywall for the ceiling. This should bring my ceiling height down to about 89 inches.

I was also planning to do just Green Glue and double 5/8 drywall for the walls (along with sealed doors and dead vents and such)

I have gone through a lot of the Lab Test Reports regarding STC ratings. I have been unsuccessful in finding a test that states the decibel reduction for the proposed ceiling configuration for sound between 10 and 80hz. Does anyone know if such a test exists that has actual numbers vs theoretical? Or does anyone have any experience or tests of their own they can share?

I've attached some rough design images for those that like construction and design pictures.

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post #2 of 21 Old 08-20-2014, 08:09 AM
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You won't find that data ... STC does not consider frequencies that low. You'll have to find products/test reports using TL (transmission loss). Also note no two assemblies are identical and you cannot add the values together to determine the total performance of a barrier.

Dennis Erskine CFI, CFII, MEI
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post #3 of 21 Old 08-20-2014, 08:15 AM - Thread Starter
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Quote:
Originally Posted by Dennis Erskine View Post
You won't find that data ... STC does not consider frequencies that low. You'll have to find products/test reports using TL (transmission loss). Also note no two assemblies are identical and you cannot add the values together to determine the total performance of a barrier.

Thanks Dennis. I am just trying to see if the money to be spent will be worth it. I am by no means expecting to stop the low frequencies, but I was hoping they could be reduced by 15 to 20 dBs. I am beginning to think that this is not possible with what I have to work with here.
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post #4 of 21 Old 08-20-2014, 08:18 AM
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You will also want to decouple your walls which it doesn't appear you are currently planning for. These should be decoupled just like the ceiling. There are other methods to do so but since your walls are already in place then clips and channel should be added to your list too.
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post #5 of 21 Old 08-20-2014, 08:37 AM - Thread Starter
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Originally Posted by vanice View Post
You will also want to decouple your walls which it doesn't appear you are currently planning for. These should be decoupled just like the ceiling. There are other methods to do so but since your walls are already in place then clips and channel should be added to your list too.
vanice,

The walls are currently decoupled from any existing stairs/walls. I was planning to double stud the walls wherever there is no concrete foundation wall behind it.

I was assuming I would not need to be worried much about flanking or sound transfer where the walls are against the foam and concrete foundation. Is this an incorrect assumption? If so, then I might as well just go the clip route everywhere vs double studs as you've suggested.
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post #6 of 21 Old 08-20-2014, 08:57 AM
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Am I missing something in your picture? It looks like the walls are rigidly connected to the ceiling supports which are rigidly connected to the floor joists above.
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post #7 of 21 Old 08-20-2014, 09:25 AM - Thread Starter
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Quote:
Originally Posted by vanice View Post
Am I missing something in your picture? It looks like the walls are rigidly connected to the ceiling supports which are rigidly connected to the floor joists above.
You are missing nothing ... I made a bad assumption about transfer loss up the walls across the ceiling and to the supports to the joists.

Thanks for pointing that out vanice.
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post #8 of 21 Old 08-20-2014, 09:51 AM
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Sure thing. I would hate to see you go through the hassle of green glue and double drywall and not see the full benefit because your shell was not decoupled from the surrounding structure.
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post #9 of 21 Old 08-20-2014, 01:53 PM - Thread Starter
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Quote:
Originally Posted by vanice View Post
Sure thing. I would hate to see you go through the hassle of green glue and double drywall and not see the full benefit because your shell was not decoupled from the surrounding structure.
I perused through your build thread. VERY NICE!

I had ordered ~60 feet 600 LEDs which just arrived (planning to use them in the theater, but these were for an area under the deck) ... about how many feet of LED strip did you end up using?

I really like the cove lighted ceiling you did ... I don't think I have enough height in the room to do that design though
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post #10 of 21 Old 08-21-2014, 05:10 AM
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Thanks klipsch. Are you asking for everything in the room or just the soffit lighting? For the soffit I used about (3 1/2) 16ft strips. For the columns I used about (3 1/2) 16ft strips. For the riser I used (1) 16ft strip.

It would probably be pretty tight to fit a soffit in around the room with an 89" finished ceiling height but I know others on here have done it. I think mine is about 11" deep so that would put you at about 78" clr. Depending on how tall you are this may be ok. Just know that you won't be able to walk under the soffit on the riser because it will be in the neighborhood of 5'-6". Since you have some good room width (which I don't) this probably wouldn't be an issue.
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post #11 of 21 Old 08-21-2014, 05:58 AM - Thread Starter
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Quote:
Originally Posted by vanice View Post
Thanks klipsch. Are you asking for everything in the room or just the soffit lighting? For the soffit I used about (3 1/2) 16ft strips. For the columns I used about (3 1/2) 16ft strips. For the riser I used (1) 16ft strip.

It would probably be pretty tight to fit a soffit in around the room with an 89" finished ceiling height but I know others on here have done it. I think mine is about 11" deep so that would put you at about 78" clr. Depending on how tall you are this may be ok. Just know that you won't be able to walk under the soffit on the riser because it will be in the neighborhood of 5'-6". Since you have some good room width (which I don't) this probably wouldn't be an issue.
Total room lighting is what I was looking for ... thanks for all the details.

I believe you had multiple controllers with several power supplies ... does one remote work with all controllers or are they different IR receivers/remote pairs?


I will have to play around with designs to see if the cove can work ... might try to go around 4-6" in height but come out about a 12-16" ... flat and wide ... not sure what else I can do other than experiment
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post #12 of 21 Old 08-21-2014, 06:10 AM
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I bought the remote/controller combo every time I needed a controller just in case. What I found out was that I now have a bunch of extra remotes lying around because one remote will control all of the controllers without issue. They didn't cost much extra so it was cheap insurance. The only drawback is if you want to have different settings for different controllers. You need to make sure the receivers are far enough apart that they won't pick up the signal to another controller. Right now I have four receivers behind my screen. My plan is to wire them together so that I don't have to worry about hitting four locations with the remote.

The soffit is nice to be able to hide HVAC and wiring inside your soundproofed shell. Definitely look at all options before you get too far along.
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post #13 of 21 Old 08-21-2014, 06:44 AM
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Without a proper box-in-box decoupled construction, which deals not only with walls and ceiling but with the floor also, soundproofing will always be flawed I'm afraid. Low frequencies go through about anything.
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post #14 of 21 Old 08-21-2014, 07:45 AM - Thread Starter
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Quote:
Originally Posted by vanice View Post
Thanks klipsch. Are you asking for everything in the room or just the soffit lighting? For the soffit I used about (3 1/2) 16ft strips. For the columns I used about (3 1/2) 16ft strips. For the riser I used (1) 16ft strip.

It would probably be pretty tight to fit a soffit in around the room with an 89" finished ceiling height but I know others on here have done it. I think mine is about 11" deep so that would put you at about 78" clr. Depending on how tall you are this may be ok. Just know that you won't be able to walk under the soffit on the riser because it will be in the neighborhood of 5'-6". Since you have some good room width (which I don't) this probably wouldn't be an issue.
Total room lighting is what I was looking for ... thanks for all the details.

I believe you had multiple controllers with several power supplies ... does one remote work with all controllers or are they different IR receivers/remote pairs?


I will have to play around with designs to see if the cove can work ... might try to go around 4-6" in height but come out about a 12-16" ... flat and wide ... not sure what else I can do other than experiment
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post #15 of 21 Old 08-21-2014, 08:03 AM
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Here is some comments I made on my theater that might be of interest.
I can't test ceiling capability stuff though as mine is single-floor, detached.

Quote:
Here's some noise measurements of my current soundproofing (at LP unless otherwise specified).

Wall construction is:
Double 5/8's GreenGlued with soundboard, on Hat Channel, double studded, double insulated with R20 & Roxul, Double 5/8's OSB, hermetically sealed with no compromises. eek.gifbiggrin.gif

Train going by @ 1/4 mile away:

Ambient noise at outside entrance: ~55dbA, ~65dbC

Inside theater, with doors open:
~35dbA
~54dbC
Reduction: 20dbA, 11dbC

with outer door shut:
<29dbA
~50dbC
Reduction Improvement: 5dbA, 4dbC
Total Reduction: 26dbA (or better), 15dbC

with Inner door also shut:
<29dbA
<42dbC
Reduction Improvement: 0-3dbA, 8dbC
Total Reduction: 26dbA (or better), 23dbC


Normal Street traffic going by:

Ambient noise at outside entrance: 50dbA, 57dbC

Inside theater, with doors open:
~33dbA
~38dbC
Reduction: 17dbA, 19dbC

with outer door shut:
<29dbA
~38dbC
Reduction Improvement: 5dbA, 0dbC
Total Reduction: 22dbA (or better), 19dbC

with Inner door also shut:
<29dbA
<37dbC
Reduction Improvement: 0-3dbA (or better), 1dbC
Total Reduction: 23dbA (or better), 20dbC



In summary:
1) My walls usually exceed the noisefloor of the measuring gear, and equipment fans are otherwise the limiting factor.
2) You can never have too much "doorness!" biggrin.gif It's always the weakest spot.
3) Unless something LOUD is happening outside, you ain't gonna hear it, and only then it will be greatly muffled.
Quote:
So I finally got around to retesting this with 90db-A and 95db-C of fullbandwidth pinknoise inside.
Ambient noise outside was 36db-A, and 53db-C.

However, not only do I have the GG and second layer of DW added, I also have a second layer of OSB on the outside so take that into consideration.


I got 38db-A outside; that's a 52db-A reduction in noise and an increase of only 2db-A. Which is a 20db-A improvement with the GG/DW/OSB added. An nearly inaudible increase. and that's a foot away from the door!
It was 70db-C outside so that's 25db-C of fullbandwidth noise-reduction, and an increase of 17db-C (at the door again, which is the weakest spot).

I also tried shaped-noise, -3db @ 100hz, but the house next door was mowing grass so I couldn't get an accurate measurement but it was 4db better even with his noise added. So (at least) 6db of my noise is coming from frequencies below 100hz.

I also tried music at 100db-C, and got 72db at the outside door with his mowing noise added (which has louder than my system), which is still 8db better than before even with the mowing noise removed.

I was only raising the ambient 3db-C at the property line with 100db-C of music before, so it could only be even lower now, so only at the highest levels of playback would sound escaping be an issue.
I'll have to try that measurement once the mowing stops.
So up to 52db-A reduction and 25db-C reduction on music outgoing, and roughly 23dbA/C reduction of background noise incoming.

With 75ft of air (distance), a 44dbC combined total reduction.

That's about the best you can expect with a structure made of wood and drywall. (i.e. not cement / brick / underground on springs)

Last edited by BassThatHz; 08-21-2014 at 08:23 AM.
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post #16 of 21 Old 08-21-2014, 08:20 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
Here is some comments I made on my theater that might be of interest.
I can't test ceiling capability stuff though as mine is single-floor, detached.
Thanks BassThatHz ... that actually is helpful info ... I won't nearly be able to do that many layers of drywall, double stud, and osb with the ceiling, but those results are excellent!

What is the "full" in "full bandwidth" pink noise ... 20hz-20KHz?

The main goal is to try and limit the noise going to the other rooms in the house ... maybe 20db reduction C weighted is not out of the question with just clips, GG, and double drywall throughout (assuming the rest of the room is done right).
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post #17 of 21 Old 08-21-2014, 08:26 AM
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Full is 1hz to 22.05khz digitally, but what comes out the actual speakers is more like 7hz to 19khz.

You can expect good results above 200hz. Below that, only god knows until you measure the final product real-world...
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post #18 of 21 Old 08-21-2014, 10:11 AM
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Quote:
Originally Posted by klipsch View Post
Hello all ... I am in the process of framing out a theater room in the basement.

Room is currently about 15'6" x 22'. Current height of the room is 92 inches (distance between concrete floor and framed ceiling).

Distance between the basement framed ceiling and the sub-flooring for the floor above is about 2 1/2 feet.

I was planning to do furring channel, clips, Green Glue, and double 5/8 drywall for the ceiling. This should bring my ceiling height down to about 89 inches.

I was also planning to do just Green Glue and double 5/8 drywall for the walls (along with sealed doors and dead vents and such)

I have gone through a lot of the Lab Test Reports regarding STC ratings. I have been unsuccessful in finding a test that states the decibel reduction for the proposed ceiling configuration for sound between 10 and 80hz. Does anyone know if such a test exists that has actual numbers vs theoretical? Or does anyone have any experience or tests of their own they can share?

I've attached some rough design images for those that like construction and design pictures.

Attachment 220602
Attachment 220610
Attachment 220618
Attachment 220626
Hi Klipsch,

I recorded a video response with my views to the issues you raised. You can see it here:

Hope it helps.

Thanks
Dennis

Chief Acoustic Engineer at Acousticfields.com. Listen to your music...without hearing your room!
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post #19 of 21 Old 08-21-2014, 10:30 AM
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BassthatHZ

"Double 5/8's GreenGlued with soundboard, on Hat Channel, double studded, double insulated with R20 & Roxul"

I've looked at your build thread and my conclusion is that you did not decouple your double drywall walls from the structures framing. It appears that you screwed your channels directly to the studs which makes firm connections at each stud and the stud walls appear be firmly connected at the ceiling joist locations. This is not room within a room isolation. It is good you got benefit from your design, it could have been better.


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post #20 of 21 Old 08-21-2014, 10:44 AM
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Dennis isn't the only one that can make a video, I made one a couple years back showing the spring action of a truly decoupled drywall assembly. This is a clips, hat channel and two layers of 5/8 design.

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post #21 of 21 Old 08-21-2014, 11:17 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
Full is 1hz to 22.05khz digitally, but what comes out the actual speakers is more like 7hz to 19khz.



You can expect good results above 200hz. Below that, only god knows until you measure the final product real-world...
Thanks BassThatHz. I really appreciate your real world numbers and experiences.



Quote:
Originally Posted by dennisfoley View Post
Hi Klipsch,



I recorded a video response with my views to the issues you raised. You can see it here:

http://youtu.be/RFPQbJaC-fo



Hope it helps.



Thanks

Dennis
Thank you Dennis. As I previously mentioned, I am interested in real world results of "sub" frequency attentuation to mitigate those sounds in the rest of the house. Low frequencies getting out to the top story of the house is a larger concern than sounds coming in to the room from a neighbor's lawn mower or HVAC unit. I was hoping to see what could be acheived in test labs or the real world (what BassThatHz shared)



Quote:
Originally Posted by BIGmouthinDC View Post
Dennis isn't the only one that can make a video, I made one a couple years back showing the spring action of a truly decoupled drywall assembly. This is a clips, hat channel and two layers of 5/8 design.



Wow! Thanks for sharing that. Very interesting to watch.

Does that flexion/movement of the channel in the clips help attentuate the frequencies via heat conversion or by increasing reflection or other?
I always assumed the channel did the flexing, not that the channel actually moved and flexed in the clips themselves ...
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