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TL through wall then floor...
Old 9th August 2019
  #1
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TL through wall then floor...

This question was on the end of another thread which isn't getting noticed, so I thought I'd re ask here. Please refer to the attached diagram, it shows a Control Room on the left and a floated studio on the right. It is to be built on an upper level with no levels above. I am ONLY concerned with the low frequency (sub 250 hz) TL via the studio through the existing slab floor, both through the floated floor and through the wall to the control room and then through the floor. I'm even concerned with the sound leaking through the gap between the 2 walls and down through the existing slab.

I'd like the studio walls to be clad with 60kg/m2 materials (probably compressed cement sheet) but if it can be shown that 35kg/m2 is sufficient, that will keep my Structural Engineer (and my neighbours below) very happy. My proposed compromise is that these walls might be 35kg/m2 except for the bottom 500mm which might be 60kg/m2. The idea for this comes from the fact that the further away 2 leaves are from from each other, the greater the TL. This is surely why, when considering only TL through a floor, that a wall can be less dense that a floor, and a ceiling can be less dense than a wall. Obviously if we're concerned with TL through the wall, or ceiling, then consistent density is imperative. But as my concern is only regarding TL through the floor, I'd like to know if its true that the bottom part of a wall being heavier than the top part will make a difference to what eventually leaks through the floor on the other side of the wall. The higher up the wall, the greater the distance between said wall section and the floor. If this is true, then maybe I can have the bottom 500mm of the wall at 60kg/m2 in density, and the rest of the wall up to the inner ceiling might be only 35kg/m2.

Does this make sense? Or is there some principle that can demonstrate how this "heavy bottom / light top" wall idea would make little difference. Remember, I'm only concerned about leakage through the floor (loud drums, bass amps etc). I don't mind leakage through to the control room, and leakage elsewhere on my level is also not an issue.

Thanks.
Attached Files
File Type: pdf heavy bottom wall best.pdf (207.4 KB, 26 views)
Old 9th August 2019
  #2
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Either hire a professional or do a lot learning. Study IR-761 all thin wall walls have mediocre low frequency transmission loss.
Old 9th August 2019
  #3
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I hired a professional - he said 35kg would work. People on forums like this one have said I need at least 60kg. Pardon me for being confused... As for reading, I can't find any book that addresses this question. I was hoping that someone on the forum had experience enough to advise.
Old 9th August 2019
  #4
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Quote:
Originally Posted by princeplanet View Post
I hired a professional - he said 35kg would work. People on forums like this one have said I need at least 60kg. Pardon me for being confused... As for reading, I can't find any book that addresses this question. I was hoping that someone on the forum had experience enough to advise.
If there was a simple single book I would have recommended it.

Thanks for the non gratitude for the truth.
Old 10th August 2019
  #5
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Quote:
Originally Posted by avare View Post
If there was a simple single book I would have recommended it.

Thanks for the non gratitude for the truth.
Sorry, certainly wasn't my intention to seem ungrateful! The question was about how sound leaks through a wall, and THEN through the floor on the other side. Reading up on TL through walls only doesn't address this. My acoustician showed me a spreadsheet that tried to explain why 35kg/m2 would be enough and commensurate with the 180kg/m2 for the floated floor, at least as far as TL through the floor on the other side of the wall is concerned. He says he does studios but I think he mainly does industrial work, so I'm not confident I can trust his assessment. I have been working with him for 2 years now, and cannot afford another professional opinion.

I thought this forum might offer some different opinions?
Old 10th August 2019
  #6
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BTW - What do you consider to be a "thin" wall? The best performing wall in the Canadian tables you referred to (which I have studied many times) is attached.
Note that the low frequency TL is reasonable. Also note that the density is only 23kg/m2. I am considering 35kg/m2 to be too light, and am contemplating 60kg/m2 as sufficient. (or maybe 60kg/m2 for the lower part of the wall and 35kg/m2 for the rest?).

Again, if I have a floated floor of 180kg/m2 and a wall on the edge of this floor, what would the density of this wall need to be for it to be commensurate with the T/L of the 180kg/m2 floor? May I remind you that I'm only concerned about the T/L loss through the existing floor slab, not the other side of the wall.

Anyone?
Attached Thumbnails
TL through wall then floor...-tl-walls.jpg  
Old 10th August 2019
  #7
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If you have a construction of 180 kg and a construction of 35 kg and you consider that a chain is as strong as the weakest link, what do you think?
Old 10th August 2019
  #8
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Quote:
Originally Posted by bert stoltenborg View Post
If you have a construction of 180 kg and a construction of 35 kg and you consider that a chain is as strong as the weakest link, what do you think?
+1. So true.

Sort of like building an aquarium with glass on the front, but pegboard on the sides...
Old 10th August 2019
  #9
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Quote:
Originally Posted by bert stoltenborg View Post
If you have a construction of 180 kg and a construction of 35 kg and you consider that a chain is as strong as the weakest link, what do you think?
Well, I happen to agree! So, if you feel 35kg/m2 to be insufficient, what would be your minimum suggested wall density? Or do you think the 180kg/m2 floor is too much?

And do you think that a heavier lower wall (as per the relevant attachment) will make a difference to the low freq TL through the floor?
Old 10th August 2019
  #11
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Quote:
Originally Posted by bert stoltenborg View Post
Thanks! Saves me needing to provide the background (yep, been looking to do this for over 2 years..)

Mind you, things have changed since then, the 7th floor neighbours are no longer an issue, just the 6th. The floating floor density of 180kg/m2 has been okayed by the SE and the location of the proposed walls are now to be resting within 400mm of the structural beams beneath the existing slab. I am about to find out what the max permissible wall density will be and am hoping to have a contingency plan ready to shoot back at the SE before he goes into hiatus again (it seems to take months for him to answer any new questions..)

Attached are 2 mud sketches for the proposed build, one is a close-up of the rooms in question.

I'd sure appreciate some thoughts re the OP.
Attached Thumbnails
TL through wall then floor...-x-send.jpg   TL through wall then floor...-aug-2019-e.jpg  
Old 1st September 2019
  #12
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Turns out that there is a way to predict the answers I was asking, despite the limited information, and I was thankfully given it on another forum by a veteran studio designer.

Just wanted to say thanks to those on this forum that tried to help.
Old 2nd September 2019
  #13
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Quote:
Originally Posted by princeplanet View Post
Turns out that there is a way to predict the answers I was asking, despite the limited information, and I was thankfully given it on another forum by a veteran studio designer.

Just wanted to say thanks to those on this forum that tried to help.
So you are keeping the answer to yourself? That is not the way forums work helping people.
Old 2nd September 2019
  #14
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Northward's Avatar
Quote:
Originally Posted by princeplanet View Post
Turns out that there is a way to predict the answers I was asking, despite the limited information, and I was thankfully given it on another forum by a veteran studio designer.

Just wanted to say thanks to those on this forum that tried to help.
I hope it's not the "answer" I gave you on PRW because as I told you there:

This is totally theoretical and I would not and do not advise using these numbers in a real situation.

Frankly, it would be stupid to use these numbers. They are the bare theoretical minimum.

I'm also a bit disturbed by the way you're shopping around on all forum for "answers" to questions that are way beyond the scope of internet discussion boards and must absolutely be calculated and validated by officially hired professional structural engineers and acousticians as there is a risk to building tenants safety and comfort.

It's not because a beam can withstand such loads that the whole building can. In most our non-ground floor (industrial) projects, the structural issues did not come from the local floor beams but from the girders, load bearing walls and/or foundations that could not sustain such cascaded loads.

As I also told you on PRW: hire someone.
Old 2nd September 2019
  #15
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Quote:
Originally Posted by Northward View Post
I hope it's not the "answer" I gave you on PRW because as I told you there:

This is totally theoretical and I would not and do not advise using these numbers in a real situation.

Frankly, it would be stupid to use these numbers. They are the bare theoretical minimum.

I'm also a bit disturbed by the way you're shopping around on all forum for "answers" to questions that are way beyond the scope of internet discussion boards and must absolutely be calculated and validated by officially hired professional structural engineers and acousticians as there is a risk to building tenants safety and comfort.

It's not because a beam can withstand such loads that the whole building can. In most our non-ground floor (industrial) projects, the structural issues did not come from the local floor beams but from the girders, load bearing walls and/or foundations that could not sustain such cascaded loads.

As I also told you on PRW: hire someone.
Yes of course, totally understood. Will hire a different "expert" this time and report back if I have any more concerns. Thanks again.
Old 2nd September 2019
  #16
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Quote:
Originally Posted by Northward View Post
It's not because a beam can withstand such loads that the whole building can. In most our non-ground floor (industrial) projects, the structural issues did not come from the local floor beams but from the girders, load bearing walls and/or foundations that could not sustain such cascaded loads.
+1
In addition, and I'm not sure what the seismic situation is in Melbourne, but where I live (Chile - earthquake capital of the world) you would never get a building permit for something that involves adding many thousands of kilograms of mass concentrated at the top of a tall building, without getting approval from a seismic engineer as well as a structural engineer. All that extra mass up there in an earthquake, even a relatively small one, could do serious damage to the rest of the structure. A floated floor with dozens of tons of mass resting on springs, is going to be slamming around all over the place in a quake if the frequency is right. Most earthquake vibration frequencies are well below the audio spectrum... often measured in single digits ... perhaps even around what the tuned resonant frequency of the floating system would be. I haven't heard anyone else mention seismic snubbers for this potential build...

Melbourne had a 5.2 quake not that long ago... and has had quite a few 4.x quakes over the last 20 years or so...

- Stuart -
Old 2nd September 2019
  #17
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He's hunting for guys telling him what he wants to hear.
Don't give him attention.
Go give serieus people 3000 word answers or go surfing.
Old 3rd September 2019
  #18
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Quote:
Originally Posted by bert stoltenborg View Post
He's hunting for guys telling him what he wants to hear.
Don't give him attention.
Go give serieus people 3000 word answers or go surfing.
Bert, I think you mean well, but you're out of line here. FWIW, it's because I've been skeptical of professional advice I've had that I visit these forums, and if anything I'm "hunting" for nay sayers more than I am for yay sayers!

But let's just say that some nay sayers are more helpful than others...
Old 3rd September 2019
  #19
Gear Addict
 

You want something that can not be done, done.

But keep us informed.

(I hope I didn't post to much today, or Thomas will consider me a lazy assed ***** ripping the bank account of my girlfriend and being of no use at all )
Old 3rd September 2019
  #20
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Quote:
(I hope I didn't post to much today, or Thomas will consider me a lazy assed...)
I don't think you reach 3000 words yet today, so you should be OK... Unless your quota is smaller than mine!

- Stuart -
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