New graphical room mode calculator

Ethan Winer

Ethan Winer

Acoustics Expert
Folks,

There are many freeware and web-based room mode calculators, but all the ones I've seen just list a table of the modes, so you still have to plot them by hand on semi-log graph paper to see how even they are. Or they require you to own Excel. Here is a link to a room mode calculator I wrote (only 36 KB to download):

www.ethanwiner.com/MODECALC.EXE

It runs in DOS and it's not fancy, but it plots the first ten primary room modes graphically so you can easily see how the modes are distributed and how they relate to one another. Instructions at the top of the screen explain how to use it - enter the Length, Width, and Height using the Tab key to go between fields, then hit Enter to see the result. The modes for each dimension are displayed in a different color, and when two or more modes occur near the same frequency the duplicates are shown on a separate line so one does not hide the other. It also lists the three ratios commonly accepted as "ideal" along with the ratio for the dimensions entered, for easy comparison.

--Ethan
 
HD,

> Can't get it to run on Win2K <

What happens when you run it? Any error messages?

I was careful to stick with the most basic programming commands, just to avoid problems with newer versions of Windows.

--Ethan
 
dumb question?

What does this accomplish? What is a room mode?

Daf (napping the day this got covered in class, I guess)
 
Re: dumb question?

Daf,

> What does this accomplish? What is a room mode? <

It's never dumb to ask a question. Here's the short answer:

Room modes are natural resonances that occur in a room, and whose frequencies depend on the distances between the sets of parallel walls, and the floor to ceiling distance. A "good" room has ratios of length, width, and height that spread these resonances around evenly. A bad room has large gaps between frequencies, and/or has multiple resonances clustered at the same or nearby frequencies.

My ModeCalc program displays the mode distribution graphically, so you can easily see how close or far apart the resonances are in any regular rectangular room.

--Ethan
 
Folks,

The final version of my Graphical Room Mode Calculator is now on my site:

www.ethanwiner.com/MODECALC.EXE

Several people have suggested improvements, which I have incorporated, and instructions are now included along with a tutorial explaining room modes.

--Ethan
 
...if you had a "rough opening", in other words bare concrete walls 28' wide by 26' long by 9' high, what size live room would you build inside of that space that would be optimal reflection wise?...
 
Fonts,

> what size live room would you build <

Given that much space to start with I'd make it as big as possible. The largest recommended ratio is 1: 1.50 : 2.50 so using 9 feet for the height "1" you get Length = 22.5 and Width = 13.5.

If you don't want to give up that much of the total space for the live room, do the same thing using the smaller recommended ratios. But if you go much smaller you'll lose the acoustical benefits of having a large room. If it were me I'd use the one large room as a combination live room and control room, and maybe put a vocal booth in the remaining space.

--Ethan
 
question for Ethan ...

for my home studio, I had a gambrel style second floor put on my 24 x 24 garage. At this point, I have the entire area open, as this is just a personal project, and I don't expect to ever go into having clients, I was not planning to do a seperate control room.

MY question - being a gambrel shape, the front wall and back wall are parallel, but both side walls slope in - the outer steep portion of the gambrel comes in for 4 ft on each side, then breaks over at 7 ft height to the upper roof section slope, and the ceiling is raised up into that, so that I have 2 seperate angles on the side walls, and I have about 12 ft width of 9 ft high ceiling running front to back.

Will your Mode calculator run on this?

thanks

b-h
 
Re: question for Ethan ...

B-H,

> Will your Mode calculator run on this? <

No mode calculator that I know of can give useful info with so many angles. One good thing about a room shaped like that is the angles greatly reduce echo problems, and probably reduce modal problems generally. Though the 24x24 dimensions are a problem.

As I explain in the summary at the end of the Help file, calculating modes is useful mainly when designing a new space. Your space is what it is, so don't obsess over what it could be. Just treat it as best you can manage. With enough treatment a room that large can give fine results.

--Ethan
 
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