John Sayers' Design Forum

John Sayers' Recording Studio Design Forum

A World of Experience
Click Here for Information on John's Services
It is currently Wed Jun 16, 2021 5:08 pm

All times are UTC + 10 hours




Post new topic Reply to topic  [ 52 posts ]  Go to page Previous  1, 2, 3, 4  Next
Author Message
PostPosted: Sat Mar 07, 2020 3:43 am 
Offline

Joined: Wed Jun 30, 2004 2:53 am
Posts: 154
Location: Achterhoek, Netherlands
Bastiaan wrote:
bert Stoltenborg wrote:
How is that second wall constructed?\
OSB-gap-brick with what dimensions?


Its two times 18mm OSB on a 2x4 wood stud frame, with the gap between the frame and the brick being 16 cm filled with insulation


That gives you if it's all decoupled something like:

25 - 21.2
31.5 - 18.5
40 - 26
50 - 27.9
63 - 41.2
80 - 45.6
100 - 46.8
125 - 49.1
160 - 48.7
200 - 56.7
250 - 59.8
315 - 63.5
400 - 69
500 - 75.3
630 - 78.2
800 - 82
1000 - 83
1250 - 90
1600 - 93
2000 - 98

Limestone wall 100 mm, 160 mm Rockwool 204 filled gap, 2 x 12,5 mm sheetrock on studs.


Report this post
Top
 Profile  
 
PostPosted: Sun Mar 08, 2020 9:24 pm 
Offline

Joined: Sun Mar 01, 2020 1:04 am
Posts: 24
Location: The Netherlands
Hi guys,

Bert provided some TL numbers which should be representative for one of my design options which are much less pleasing than the numbers from the MSM TL calculator V2.03. As a reference, I have a document with empirical data from the BBC about brick partition walls, which show a ~30dB TL at LF for a double brick wall. It was too large to attach it, but you can download it here: http://downloads.bbc.co.uk/rd/pubs/arch ... itions.pdf

I took the effort to model the TL formula's in excel. I used an extract from the book "Architectural Acoustics by Marshall Long".
It can be downloaded here: https://ocw.upj.ac.id/files/Textbook-AR ... NGUNAN.pdf

These are the results I get:
Attachment:
TL calc BPE.jpg


The formulas model ideal panels with no connections, flanking, etc, and ideal damping, so the output should be considered the maximum you can achieve. So a real world design will be worse than what the calculations predict.

The MSM TL calculator 2.03 is more optimistic in the LF part than the formulas predict and the empirical BBC data shows for double brick walls:
Attachment:
TL calc stone.jpg


Is it possible that there is a coding error in the LF part of the MSM TL Calculator v2.03? Or did I not fill it in correctly?
I have attached my excel file in case anyone is interested.


You do not have the required permissions to view the files attached to this post.


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 09, 2020 5:19 am 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1501
Location: St. Albert, Alberta, Canada
Quote:
The formulas model ideal panels with no connections, flanking, etc, and ideal damping, so the output should be considered the maximum you can achieve. So a real world design will be worse than what the calculations predict.

The MSM TL calculator 2.03 is more optimistic in the LF part than the formulas predict and the empirical BBC data shows for double brick walls

Exactly, the formulas in the calculator are based on 3 frequency bands as you can see in the formulas at the bottom of the calculator. Feel free to open up the data tab an check through it yourself if you'd like. The BBC document is showing real life builds and those are obviously closer to results forum members would experience as builds are never absolutely perfect and things like HVAC, doors and windows can really screw up isolation.

Quote:
Is it possible that there is a coding error in the LF part of the MSM TL Calculator v2.03? Or did I not fill it in correctly?

I have checked the formula entries countless times and am 99.9% confident in it calculating those formulas correctly.

Quote:
I have attached my excel file in case anyone is interested.

This is great! It makes me question if I should exchange the formulas in my calculator for the Marshall Long formulas. Thanks!

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 09, 2020 6:41 am 
Offline

Joined: Wed Jun 30, 2004 2:53 am
Posts: 154
Location: Achterhoek, Netherlands
Gregwor wrote:
Quote:

Quote:
Is it possible that there is a coding error in the LF part of the MSM TL Calculator v2.03? Or did I not fill it in correctly?

I have checked the formula entries countless times and am 99.9% confident in it calculating those formulas correctly.



Greg


Come on, dude, get a life.
Where the f*ck is Stewie?


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 09, 2020 8:35 am 
Offline

Joined: Sun Mar 01, 2020 1:04 am
Posts: 24
Location: The Netherlands
Hi Greg,

Glad you are not offended by my question :)

I think I found the difference.

Attachment:
TL_calc_coding.jpg


In the formulas in the C and D column, you add the transmission loss of each leaf (R1 + R2) + some frequency dependent term, according to the formulas on the first page. The issue is that R1 and R2 themselves are also frequency dependent, but you refer to a fixed value which is on the first page.

Kind regards,

Bastiaan


You do not have the required permissions to view the files attached to this post.


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 09, 2020 8:57 am 
Offline

Joined: Sun Mar 01, 2020 1:04 am
Posts: 24
Location: The Netherlands
I have been thinking about a good floor this weekend.

I still intend to use a floor like this:

Attachment:
Broodjesvloer.png


The easiest way to have the studiofloor decoupled from the rest of the building would be like this:

Attachment:
fundering gezamenlijk forum.jpg


This comes with no cost adder. However, the foundations are shared, and therefore there is a flanking path from one floor to another: floor1 surface -> Tbeam floor 1 -> common foundation Tbeam floor 2 -> floor 2 surface. This technique is used for townhouses/terraced houses.

Bert suggested earlier that a decent floor should have a separate foundation. So the second option is this:

Attachment:
fundering gescheiden forum.jpg


This option comes with a cost adder in additional concrete for the foundation beams, and some additional piles. Also, it is a bit more difficult to build. I have limited real estate, so the distance between the foundations must be very small, I took 4 cm in the drawing. Therefore I think I cannot pour both foundations in one go. On the other hand, I like engineering challenges :D

Is there any way to predict the difference in TL with the two options? I think option 2 will cost me about 2k euro's more, so it would be nice if I could justify this cost.


You do not have the required permissions to view the files attached to this post.


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 09, 2020 9:33 am 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1501
Location: St. Albert, Alberta, Canada
Quote:
Hi Greg,

Glad you are not offended by my question :)

I think I found the difference.

Thanks for the time you've put in to everything man. I will try to find some time to dig into this further. I'm not sure why Bert is so butt hurt. We are a community trying to help one another and it's extra effort like you've put in that makes everyone prosper. So again, thank you!

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 09, 2020 9:38 am 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1501
Location: St. Albert, Alberta, Canada
Quote:
Come on, dude, get a life.

What are you referring to? Myself and others tested the calculator for weeks before releasing it.

Quote:
Where the f*ck is Stewie?

Running his own forum.

Please be respectful from here on out.

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 09, 2020 11:16 am 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1501
Location: St. Albert, Alberta, Canada
UPDATE:

I have fixed the calculator but have 2 small items I'm waiting for my partner audiomutt to address for me. Hopefully I will have the updated version posted soon.

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
PostPosted: Mon Mar 09, 2020 11:55 pm 
Offline

Joined: Wed Jun 30, 2004 2:53 am
Posts: 154
Location: Achterhoek, Netherlands
Gregwor wrote:
Quote:
Come on, dude, get a life.

What are you referring to? Myself and others tested the calculator for weeks before releasing it.

Quote:
Where the f*ck is Stewie?

Running his own forum.

Please be respectful from here on out.

Greg


Sorry, I should have used a smiley.
But a calculator that calculates such numbers should really not be on a respectable forum.


Report this post
Top
 Profile  
 
PostPosted: Tue Mar 10, 2020 12:01 am 
Offline

Joined: Wed Jun 30, 2004 2:53 am
Posts: 154
Location: Achterhoek, Netherlands
Bastiaan wrote:
I have been thinking about a good floor this weekend.

I still intend to use a floor like this:

Attachment:
Broodjesvloer.png


The easiest way to have the studiofloor decoupled from the rest of the building would be like this:

Attachment:
fundering gezamenlijk forum.jpg


This comes with no cost adder. However, the foundations are shared, and therefore there is a flanking path from one floor to another: floor1 surface -> Tbeam floor 1 -> common foundation Tbeam floor 2 -> floor 2 surface. This technique is used for townhouses/terraced houses.

Bert suggested earlier that a decent floor should have a separate foundation. So the second option is this:

Attachment:
fundering gescheiden forum.jpg


This option comes with a cost adder in additional concrete for the foundation beams, and some additional piles. Also, it is a bit more difficult to build. I have limited real estate, so the distance between the foundations must be very small, I took 4 cm in the drawing. Therefore I think I cannot pour both foundations in one go. On the other hand, I like engineering challenges :D

Is there any way to predict the difference in TL with the two options? I think option 2 will cost me about 2k euro's more, so it would be nice if I could justify this cost.


Didn't I post the differences? :-)


Report this post
Top
 Profile  
 
 Post subject: Reality
PostPosted: Tue Mar 10, 2020 2:52 am 
Offline
Senior Member

Joined: Tue Mar 25, 2008 3:31 am
Posts: 521
Location: Cork Ireland
Almost all of my work is remedial or treating existing structures. For one green field build I ticked every box possible, with approval from all 4 Criteria in ModeWiz. I optimised to within centimetres of the planning limits. Modal pattern of the finished space bore no relationship with the predicted.
Pondering this I note probable systemic errors in other predictors/calculators.
For example:-
Sound travels on average 20% slower through fibre, but this has a spectrum and some see it as low as 80m/S at some frequencies.
So the modal pattern of a strongly treated room will be quite different to that of a concrete shoebox.

Porous absorption calculators do not deal with the corner situation, which if we extrapolate from speakers, can be a x8 factor.
Same calculators treat a layer as infinite or full surface. I do not believe the theoretical quarter wave absorption peak will hold up when a fibre trap is tiny compared to the boundary.
And what happens when we distribute such tiny traps, do we bunch them together to form a bigger sheet, or strategically gap them?
And how does this interact with the air gap to boundary distance?

At studiotips we see a Corner Straddling batt of 703. Touching the wall it has a pretty massive absorption peak around 80Hz or so.
Moved out a bit from the wall about 2 inches this collapses? Was this a fully sealed straddler, floor to ceiling? Or do single traps benefit this much in this position.
Again, full surface/corner or gaps between panels?

IMO, it is audible, denser fibres have a damped resonant effect. Calculators frequently predict little or no LF absorption as they use GFR only.
Different types of fibre appear more damped e.g. Fibreglass 705 is quite ringy while Rockwool not.
Also and by all means correct me if I am wrong, but some fibres appear to have vastly different absorption, not so related to GFR only.
e.g. Caruso Isobond, Autex.

Lastly, and maybe on point here.....

A large surface area, even concrete, will flex a whole lot more than a smaller one. Do our TL predictors take this into account?

_________________
DanDan FitzGerald MIOA MAES
http://www.irishacoustics.com
http://www.soundsound.ie


Report this post
Top
 Profile  
 
PostPosted: Tue Mar 10, 2020 5:09 am 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1501
Location: St. Albert, Alberta, Canada
Dan, you're awesome.

Quote:
But a calculator that calculates such numbers should really not be on a respectable forum.

Bert, the calculator uses basic well known formulas that any forum member here would have to do by hand in order to figure out what materials to use in their builds. It was built so that people could spend 20 seconds calculating different scenarios. The drop down boxes and conversion section make it easy to use. It takes out the research time a person would spend looking up the density of their materials. With all of that said, I'm not sure why you're so concerned with it being on here. If you build a better one that is as easy to understand and use for newcomers and post it for free, I'll gladly remove mine and sticky yours.

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
PostPosted: Tue Mar 10, 2020 6:38 am 
Offline

Joined: Wed Jun 30, 2004 2:53 am
Posts: 154
Location: Achterhoek, Netherlands
Gregwor wrote:
Dan, you're awesome.

Quote:
But a calculator that calculates such numbers should really not be on a respectable forum.

Bert, the calculator uses basic well known formulas that any forum member here would have to do by hand in order to figure out what materials to use in their builds. It was built so that people could spend 20 seconds calculating different scenarios. The drop down boxes and conversion section make it easy to use. It takes out the research time a person would spend looking up the density of their materials. With all of that said, I'm not sure why you're so concerned with it being on here. If you build a better one that is as easy to understand and use for newcomers and post it for free, I'll gladly remove mine and sticky yours.

Greg

What are you talking about?
73 dB @ 20 Hz is ridiculous.


Report this post
Top
 Profile  
 
PostPosted: Tue Mar 10, 2020 6:47 am 
Offline
Moderator
User avatar

Joined: Wed Feb 01, 2017 6:03 pm
Posts: 1501
Location: St. Albert, Alberta, Canada
Quote:
What are you talking about?
73 dB @ 20 Hz is ridiculous.

I've stated that the calculator 2.04 is fixed and releasing soon. It has taken a year and a half of version 2 out for this to come to fruition.

Greg

_________________
It appears that you've made the mistake most people do. You started building without consulting this forum.


Report this post
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 52 posts ]  Go to page Previous  1, 2, 3, 4  Next

All times are UTC + 10 hours


Who is online

Users browsing this forum: No registered users and 25 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
Powered by phpBB® Forum Software © phpBB Group