Room Mode calculator - HTML only version

[Bob]

http://www.bobgolds.com/Mode/RoomModes.htm

I might add a graph of some sort to this page.

Over at RO, Jeff listed eight calculators and later mentioned that all the easily available tangential mode calculators were dependant upon excel, and recommended a .exe.
I'm not fond of installing nor running internet .exe files, and they don't always run on Mac/Linux. The above is javascript only.

[Scott R. Foster]

OMG Bob!

It includes those pesky non-axial modes... must be one of those "old school acoustics" things [one that uses physics instead of voodoo].

[Brian Dayton]

man, that is as slick as a popsicle stick

did you whip this up just recently?

[Howler]

Hey Bob.... is this just a Mac thing that it didn't do anything when I hit "compute imperial" ?

sf

[Bob]

Brian Dayton
I did it this morning. I have several ideas for improvements.

[Bob]

Howler:
I don't have a Mac to test it on.
But I did it in javascript and not vbscript, so I would have throught that if your browser has javascript turned on it should run.

[David French]

Bob, if you could make some kind of graph, that would really kick ass.

[Dan Nelson]

Very nice. I tested it works fine on a mac. Bob I have some ideas if want try adding some type of graph. Steve Marinick's old filemaker calculator had a nice way of graphing the modes however I don't have filemaker anymore to open it. It would be nice to have screen shot of it.

Dan

[Bob]

I added colour coding if the frequencies are close to each other.

I also made the integer range automatic (a function of frequency and dimensions) to reduce compute time. (push SHOW OPTIONS to see the results).

[Bob]

Dan Nelson:
re a graph.
I was thinking of a simple logarithmic line with dots on it, and a piano keyboard under it, from 20hz to 300h.
i.e. not Eric's two dimensional graph.

Thanks for mac testing.

[Bob]

The page now has a little piano graph.

[Brian Dayton]

Brian Dayton
I did it this morning. I have several ideas for improvements.

i see you got right to work on those improvements.  it occurs to me that you have some skills there, and could probably put a whole lot of things on your site.

[Bob]

Brian Dayton

could probably put a whole lot of things on your site.-

limited by
a) ideas first  :wink:
b) time to implement second  :o
It's probably obvious, but I'm much better at programming than graphic design.  :mrgreen:

[avare]

Caught this on the tail end..

Great stuff Bob!

Andre

[Bob]

Thank's for the kudo's all.

I'm open to suggestions for additional features, or changes in the existing to match some acoustic theory or science.

I'm considering adding:
a) a room ratio calc
b) rotating the piano 90 degrees so that it could be used underneith an ETF5 plot (i.e. to match modes to measured)
c) an automatic room sizing algorithm that'll try a range of room dimensions and chug for a day to find the best 3. To answer the question: what if I made this wall a foot or two or more smaller.

[Bob]

Howler:
In case this wasn't obvious, you were my target audience, because of Studiotips thread Need nodes run ... can't find a calculator for Mac.

[DJ]

Bob,

I hope this doesn't sound stupid, but should all the modes be given equal weighting?  My understanding of Everest (Master Handbook of Acoustics), chapter 15, was that tangential modes have only 1/2 the energy of of axials, and obliques only 1/4.  Would it make sense to make the lines shorter for non-axial modes?

[Bob]

DJ:
I've read that too, but I think wether it's true or not is irrelevent. Everest says it is, and I think Jeff says it isn't, e.g. point 5 here.

The purpose of the tool/page is two-fold:
a) before the room is built to allow you to design a room that is less likely to have overlapping modes. It doesn't matter if one mode is twice as strong as the other for one reason or another, if they're they same frequency they could add up (superposition) into something serious
b) after the room is built and measured, if a troublesome frequency is found, it gives a first hint as to where to place absorbtion to treat it. Sort of a time saver. It may be right or wrong (acoustical room dimensions vs phsycial room dimensions) but it's certainly a place to start, considering how vastly little thought and time it takes to find out which axial or tangental it might be, if any.

Would it make sense to make the lines shorter for non-axial modes?

So I don't think so. A couple of variations on line size/position I was considering were:
a) splitting the lines into three with a column for axial, a column for tangental, a column for oblique -- but I decided it's redundant information on the piano graph and that the list of frequencies on the left does a much better job
b) having thicker or longer lines when two frequencies overlap -- this is a lot of programming and again is redundant because the left list of frequencies has that colour coded information.

[DJ]

Thanks for the info (and the link), Bob.

I've read that too, but I think wether it's true or not is irrelevent. Everest says it is, and I think Jeff says it isn't

What does this forum say?

[Dan Nelson]

I don't think  Everest says it is irrelevent, just lower in most cases. I agree with Jeff at some point you will run into a strange room. How close the modes are and if they are "stacking" is the more important part.

Dan