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 Sun Mar 07, 2021 3:00 am

All times are UTC + 10 hours




Post new topic Reply to topic  [ 6 posts ] 
Author Message
PostPosted: Mon Jan 04, 2021 10:57 am 
Offline
User avatar

Joined: Sat Aug 21, 2004 6:17 am
Posts: 198
Location: Montreal, Quebec, Canada
Hi everyone!, It's my first post here in more than ten years...that's a loooong time. I have a question that remains unanswered, after a some research, i thought maybe someone here could have the answer. My apologies if this has already been covered before. Here it goes. When i compare the results of a pourous material ( say 3" of Roxul Safe'n sound) using the online porous absorber calculator ( and entering all the material parameters) and the published absorption value from the manufacturer spec sheet, the results don't match. There are substantial differences mainly in the low end region. That raise the question: Who's right? The calculator or the manufacturer?

any hints welcome
regards

_________________
Eric
Orange Numerik
Montreal

Technology is just faster ways to do things we didn't have to do before !


Report this post
Top
 Profile  
 
PostPosted: Tue Jan 05, 2021 3:50 am 
Offline
Senior Member

Joined: Tue Mar 25, 2008 3:31 am
Posts: 445
Location: Cork Ireland
The Calculator/Predictor has various Models. Also try different angles of incidence. Around 70 degrees may show results closer to the measured and 'optimistic' ones.

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


Report this post
Top
 Profile  
 
PostPosted: Tue Jan 05, 2021 5:15 am 
Online
Moderator
User avatar

Joined: Wed Jul 13, 2005 3:55 am
Posts: 4772
Location: Old Tappan, NJ USA
also, bear in mind, the manufacturer is using tests based on certain industry standards - thickness, air temp, backing, humidity, etc so the results are measured to that/those specs. how that translates into performance in a given situation: best guess using a model, or empirical testing to optimize. so the published specs are just that, and they should reference the standard their testing to which usually includes fire safety, health warnings, temperature insulation, acoustics, etc etc so check their spec sheet. likely to find acoustics testing is limited down to 125hz and 1 or 2 mounting options.

_________________
Glenn


Report this post
Top
 Profile  
 
PostPosted: Tue Jan 05, 2021 8:35 am 
Offline
User avatar

Joined: Sat Aug 21, 2004 6:17 am
Posts: 198
Location: Montreal, Quebec, Canada
Dan and gulfo thank for the answer.

_________________
Eric
Orange Numerik
Montreal

Technology is just faster ways to do things we didn't have to do before !


Report this post
Top
 Profile  
 
PostPosted: Wed Jan 06, 2021 5:51 am 
Offline

Joined: Tue Sep 15, 2020 7:52 am
Posts: 4
DanDan wrote:
The Calculator/Predictor has various Models. Also try different angles of incidence. Around 70 degrees may show results closer to the measured and 'optimistic' ones.


When you say "measured" are you talking about in practice or in the labs?

Which is the best for predicting real world outcomes?


Report this post
Top
 Profile  
 
PostPosted: Wed Jan 06, 2021 10:11 am 
Offline
Senior Member

Joined: Tue Mar 25, 2008 3:31 am
Posts: 445
Location: Cork Ireland
Measured in the Labs. I also think 70 degress is quite representative quite a bit of the real world incidence.
Lab tests are typically done to standards which are not optimised to represent our use. They typically don't include an airgap. The area of tested absorber is typically contiguous, omitting the effect of multiple exposed edges in our word. Finally we avail of the vast magnification of corner placement. Labs stay away from corners.

The models used in the online predictor are from Lab Testing afaik.

Over time one gets to see manufacturers claims, studio build results ongoing, etc. etc. One gets an averaged sense.
I would trust the predictor to select the optimum GFR for the varous thicknesses. But also remember the 'drumhead' damped membrane effect of corner staddling rigid fibre.
And the lack of it with fluffy deep traps.

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


Report this post
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC + 10 hours


Who is online

Users browsing this forum: No registered users and 37 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