Room Mode calculator - HTML only version

Post and discuss acoustic topics, Studio design, construction, and soundproofing here

Postby kg2kg » Mon Apr 18, 2005 3:38 pm

Bob,

Wonderful tool you have built!  I am on a Mac (Safari) it is very nice to use.  Some questions, on the Bonello graph, neither x or y axis title or scale info show up?

I am in Colorado, so there is an altitude effect on how fast sound travels.  You are taking into account temperature (I think from reading your earlier posts), what about adding a elevation option as well!

What about ceiling insulation treatment for 1st reflections affecting the Sabin calculations?

Thanks again for all your effort!

Kevin
kg2kg
 
Posts: 9
Joined: Sat Jan 22, 2005 7:11 pm

Postby Bob » Mon Apr 18, 2005 4:44 pm

kg2kg:

Wonderful tool you have built!  I am on a Mac (Safari) it is very nice to use.  Some questions, on the Bonello graph, neither x or y axis title or scale info show up?

I'm using CSS like HTML style commands in my html to position the scale (absolute position, top,left), which it seems a few browsers don't support.
I had the same problem with the colours on the frequency chart, and had to go to .GIF files instead.
I'm not sure how to solve this just yet.

I am in Colorado, so there is an altitude effect on how fast sound travels.  You are taking into account temperature (I think from reading your earlier posts), what about adding a elevation option as well!

Sounds like it should be an option for you to enter the speed of sound. There's also humidity that affects the speed.

What about ceiling insulation treatment for 1st reflections affecting the Sabin calculations?

What did you have in mind? (words and algebra)
My first instinct is that First Reflections (either ceiling or walls) become a bit tricky to estimate for widly spaced stereo, even more widely spaced 5.1 front 3 speakers, and optimized/quantized for 2'x4' sizes that rigid material seems to come in.

I'm thinking about an 'explanations and references' link, but work is keeping me busy.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby kg2kg » Mon Apr 18, 2005 8:03 pm

Bob,

Sounds like it should be an option for you to enter the speed of sound. There's also humidity that affects the speed.

I see various calculators on the web, at 5500 ft, the sound is about 2% slower?  I also found references that humidity, and pressure tend to cancel out the speed differences? So, it looks like mile high and dry Colorado isn't going to affect it very much!

I did find one mode calculator with the speed in it...  
http://harman.com/wp/index.jsp?articleId=131

What did you have in mind? (words and algebra)
My first instinct is that First Reflections (either ceiling or walls) become a bit tricky to estimate for widly spaced stereo, even more widely spaced 5.1 front 3 speakers, and optimized/quantized for 2'x4' sizes that rigid material seems to come in.


I would agree, it would be different for every room and speaker layout, I guess in your commentary you might talk that adding ceiling insulation does affect the RT60.  I assume it would be in the area of calculation, of Surface Area   (sabins - front wall - carpet - ceiling (%covered x area) ) / Left+Right+Rear wall:  xx%  <- is that correct?

I'm thinking about an 'explanations and references' link, but work is keeping me busy.


That would be great, I like the idea you had in suggesting a bad room (10x10x10) and then a small change really affects the data.  Maybe you could follow it through in explaining the rest.

Great job!  Kevin
kg2kg
 
Posts: 9
Joined: Sat Jan 22, 2005 7:11 pm

Postby Bob » Mon Apr 18, 2005 9:16 pm

kg2kg:

(sabins - front wall - carpet - ceiling (%covered x area) ) / Left+Right+Rear wall:

The line with the 'carpet' was for home theater owners, who tend to cover their floors with carpet no matter what.
If you want to cover the ceiling with stuff, then you can use the existing carpet line, since most rooms ceiling has the same ft^2 as the floor.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby kg2kg » Tue Apr 19, 2005 12:22 am

Bob


The line with the 'carpet' was for home theater owners, who tend to cover their floors with carpet no matter what.
If you want to cover the ceiling with stuff, then you can use the existing carpet line, since most rooms ceiling has the same ft^2 as the floor.


Thanks for the clarification,

Kevin
kg2kg
 
Posts: 9
Joined: Sat Jan 22, 2005 7:11 pm

Postby Bob » Tue Apr 19, 2005 6:56 am

Hello

http://www.bobgolds.com/Mode/RoomModes.htm
I think is just about done now in terms of the features I wanted.
I've added the corresponding link to www.bobgolds.com

Today's improvements.
a) fixed the Walker computation bug
b) added a TextArea with the chart in tab separated text, which is easy to copy/paste into Excel
c) the beginnings of an explanation/notes/references page, but no point in reading it just yet.
d) a few new calculations:

Schroeder Fc: 138hz
Frequency Regions:
- No modal boost: 1hz to 45hz
- Room Modes dominate: 45hz to 138hz
- Diffraction and Diffusion dominate: 138hz to 552hz
- Specular reflections and ray accoustics prevail: 552hz to 20000hz

The Frequency Regions are from Master Handbook Of Acoustics pg 324 figure 15-7
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby Bob » Wed Aug 03, 2005 3:42 pm

Someone PM'ed asking

I was wondering if you gave any thought to making your room mode calculator into a stand alone program so that we could use it when not connected to the web?  There are many times I am at a clients house and take a quick room measurement of a potential room, but have to wait until I get home to see the results of those dimensions.

It would be great if I could do it right there on the spot to let the clients know how their room fares from the start.


Since it's all html/javascript, as long as all the files (.gifs) it needs are cached, a browser (internet explorer etc) should be able to handle it off line.

But just in case it can't, to make sure, you can now download
   http://www.bobgolds.com/Mode/RoomModes.zip
and unzip the files to a directory and open RoomModes.htm
and that definately will work off line.

(I don't know if I'll be keeping the zip file up to date if I spot and fix any bugs in the main source -- certainly I won't keep it up to date on everyone's personal hard disk. )
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby Bob » Thu Aug 04, 2005 11:56 pm

A bug in the Walker calculation has been fixed.
Website and Zip file updated.
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby Bob » Fri Feb 24, 2006 10:11 pm

A bug in the handling of metric has been fixed at jonessy's request.

I also added two buttons "Convert to Metric" and "Convert to Imperial"
The idea is that on forums like this one, some of us think in imperial, and some of us think in metric.
So if someone specifies their room dimensions in either, you can type in the dimensions that they give as stated and run them, and then press the corresponding "Convert to" and run them again in the other system, and suddenly you have cut-and-pasteable both imperial and metric for that room.

http://www.bobgolds.com/Mode/RoomModes.htm
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby jonessy » Sat Feb 25, 2006 12:18 am

Thanks Bob.  :)
jonessy
 
Posts: 580
Joined: Wed Jan 04, 2006 3:39 pm
Location: Israel

Postby Dan Duskin » Sat May 20, 2006 7:10 am

I've been using your Calc a lot Bob, it's been a big help. I also just received RPG's Room Sizer software.

I heard you say you like to use more than one calculation tool for this. Do you have any recommendations? I figure if I can get something that looks good on your calculator, room sizer, and a 3rd calculator I'm probably really on to something. What do you think?
Dan Duskin
 
Posts: 190
Joined: Fri Feb 24, 2006 10:20 am
Location: Near Hollywood, California

Postby Bob » Sat May 20, 2006 8:29 am

Dan Duskin:

Most of the calculators use the same formula that's used on my webpage ( Lord Rayleigh's I think ), and assume (falsely) that the walls are 100% reflective. My page also includes several other formulas (Walker, Bonello, etc)
Room Sizer's 'formula' is quite different.
If you get a match with both of those, that'll do fine.

CARA is a possible third.

Dennis Erskine wrote:With respect to general issue of room size:

If one can build the room avoiding coincident modes, then that is the better choice; however, larger is better than smaller. If when examining the constraints, changing the dimensions makes the room impractical (too narrow, too low a ceiling, too short), then build the room anyway. It is doubtful, or at least questionable, that changing a dimension less than a foot is going to make a real world difference in any case. The actual as built physical characteristics of the walls, the addition of design elements, platforms, seating, and stages are going to throw their two cents into the mix and result in something different than the modal spreadsheet suggests in any case. If, when designing the room, you know in advance that you have a potential coincident modal issue, then within the design you can accommodate, or plan for the use of, any one of several mechanisms to deal with the modal problem. I would suggest an 11' wide room with no coincident modes, is less attractive than either no room, or a 13' wide room (with coincident modes) when all other needs are addressed.

...

Room modes just are. It would be nice to have all the modes equally excited, not audible, perfectly distributed, blah, blah. Sorry, that's not going to happen. You'll have modes, period. Rather you have one, five or ten, the solution set available is still the same. Move the seats, move the speakers, absorb, equalize, or turn off the amp. As I've noted several times, the spreadsheet calculators are interesting but (a) don't tell you all the information you need to know; and, (b) cause alot of arm waving and draw time and attention away from equally (if not more so) problematic (and solvable) acoustic issues during the design. Build the room. Build with some flexibility, measure the room and then fix the problem(s) you really have. Ok, so you're left with a triple coincident mode. So either fix it or have someone fix it for you. That's a far better choice than (a) no room at all; or, (b) wasting a month fretting about it at the expense of forgetting about the long list of other issues.

Layout your room to meet *your* needs of space, seating, picture size, budget, and the like and then move ahead.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby Dan Duskin » Tue May 23, 2006 9:22 am

Thanks Bob!

I'll be checking the numbers with you guys as well :)
Dan Duskin
 
Posts: 190
Joined: Fri Feb 24, 2006 10:20 am
Location: Near Hollywood, California

Postby Dan Duskin » Tue Jun 20, 2006 8:52 am

Question...

I don't quite understand the "%" part. Is that how strong the mode is? i.e., the largest "%" is the most problematic mode?

If that's the case... an option to sort by "%", or to show the top 4 or top 8 "%" in order below would be helpfull.

Cheers,
Dan
Dan Duskin
 
Posts: 190
Joined: Fri Feb 24, 2006 10:20 am
Location: Near Hollywood, California

Postby Dan Duskin » Tue Jun 20, 2006 9:05 am

Also... Just a cool idea...

What if the Tangential modes could show which 4 walls the mode is derived from...?
Dan Duskin
 
Posts: 190
Joined: Fri Feb 24, 2006 10:20 am
Location: Near Hollywood, California

Postby Bob » Tue Jun 20, 2006 2:15 pm

Dan Duskin:

The % is the frequency separation. The further apart the frequencies the worse (more noticiable).

The walls involved can be seen from the mode number. e.g. if (1,1,0) the zero tells you which surface is not used. Since the mode number is arranged as (length, width, height) in this case the tangental mode is a length-width (no height) mode. A (0,3,0) axial mode would not involve length or height (both are zero), so it is a width mode.
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby Bob » Tue Jul 11, 2006 6:48 am

I've made a change to the page.
In addition to the ITU T60, it now also calculates the IEC/AEC T60 based on the N 12-A standard, as shown in this paper
http://www.harman.com/wp/pdf/HarmanWhit ... ingLab.pdf.

RT60 (IEC/AEC N 12-A standard): 350 ms
-  ±50ms from 200Hz to 3.5kHz = 300 to 400ms
-  ±100ms above 3.5kHz = 250 to 450ms
-  <+300ms at 63hz = 650ms
-  300<RT60<600ms
RT60 (ITU/EBU Control Room Recommended): 289 ms
-  ±50ms from 200Hz to 4kHz = 239 to 339ms
-  <+300ms at 63hz = 589ms
-  200<RT60<400ms
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby Bob » Thu Oct 26, 2006 7:56 am

I added
 Critical Distance (direct = reverberant field):
to the calculations,
and fixed the bonello graph overlapping the calculations.
Bob
 
Posts: 4358
Joined: Sun Feb 08, 2004 4:37 am
Location: Oakville, Ontario, Canada

Postby tonio » Thu Oct 26, 2006 5:49 pm

Cool stuff Bob,
I was wondering about the graph covering the calculations.  Glad its fixed. Thanks for your work and contributions to the acoustical world.

T
tonio
 
Posts: 152
Joined: Sat May 29, 2004 11:28 pm
Location: San Diego, CA

Postby Euterpe » Sat Jan 06, 2007 7:02 pm

Hi everybody,

This my first post, I'm located to Quebec-Canada.

I don't be able to open on my Mac OS X, all Excel files, however Office packaging is already done for every Excel files, but not your's :cry:

May be it's because that's Excel PC file?

I must practice my english here, this is not my native language, be indulgent, thank you.
webzine for audiophile & music lover
www.magazine-audio.com
Euterpe
 
Posts: 1
Joined: Sat Jan 06, 2007 12:50 am
Location: Canada

PreviousNext

Return to Discussion

Who is online

Users browsing this forum: Yahoo [Bot] and 3 guests