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Author Topic: RT60 calculator  (Read 5361 times)

jimmyjazz

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RT60 calculator
« on: March 26, 2010, 09:25:40 pm »

I have just now recovered from an insidious virus that eventually crippled my XP box to the point where it wouldn't even boot.  No problem, I just wiped the drive and installed Windows 7.  I had Norton 360 backups of everything.

No, I didn't.  It didn't do a complete backup (unbeknownst to me).

So now I have a client needing some simple RT60 calcs by Monday, and I'd rather not code them myself, as simple as they might be.  Any hints on a website or downloadable Excel spreadsheet (virus alert!) that might have a good selection of standard absorption materials available in library format, as well as RT60 calcs based on geometric inputs (surface area and volume)?

Thanks,

ja
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Ethan Winer

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jimmyjazz

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Re: RT60 calculator
« Reply #2 on: March 27, 2010, 09:09:26 pm »

Close . . . doesn't look like I can input my own absorption data.  Thanks, though, it's a start.
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martindale

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Re: RT60 calculator
« Reply #3 on: March 27, 2010, 11:27:17 pm »

Jimmy,
I don't know an internet site that has this info because many years ago I first learned about it and did computations from a book: Master Handbook of Acoustics by Everest. The Sabine equation is in there (and many other places), and the Appendix has absorption coefficients of many common construction and acoustic materials...that's all you need to compute R60 times. I set up spreadsheets that do these calcs by inputting these coefficients and sq ft coverage.---although, it will never be exactly as you might measure in "the real world" because of several factors; such as the additional "absorbers and resonators" which will be in any studio room: such as speaker cabinets; closets; furniture and people; irregular geometries and room shell construction; all which will effect nominal R60, at different frequencies.

Everest's book does appear to be in several places on the net. You can find absorption coefficients of almost any material if you dig hard enough on the net.
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jimmyjazz

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Re: RT60 calculator
« Reply #4 on: March 28, 2010, 12:22:12 am »

Sure, I can (and have) set up a spreadsheet.  I was just being lazy.

I thought I recalled an Excel spreadsheet that has hundreds of lines of octave-band absorption data for all kinds of materials, but I can't find it.  Frustrating.
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martindale

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Re: RT60 calculator
« Reply #5 on: March 28, 2010, 11:28:36 am »

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jimmyjazz

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Re: RT60 calculator
« Reply #6 on: March 28, 2010, 04:47:42 pm »

That's it!  Thanks.  Notice the link on the Bob Gold site to Chris Whealy's website, which is where I saw some decent room acoustics spreadsheets.
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franman

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Re: RT60 calculator
« Reply #7 on: April 01, 2010, 07:39:26 pm »

Thanks for the great link Mark.. that RT60 calc (at the top) is whack... no way is it giving any reasonable results for an empty box.. Something wrong there IMO

FM
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Francis Manzella - President, FM Design Ltd.
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fmdesign.com
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jimmyjazz

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Re: RT60 calculator
« Reply #8 on: April 01, 2010, 11:15:02 pm »

Fran, which link are you referring to?  Ethan posted one up above, but I haven't checked it out to see if it passes the "sniff" test.

In my experience, it seems the Sabine equation (0.049*V/Sa) estimates an unrealistically long RT60 for larger, empty rooms, and as a practical matter, either air absorption or that of people & furniture must be brought into the calculations to get a better read on things.  What do you think?
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franman

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Re: RT60 calculator
« Reply #9 on: April 01, 2010, 11:28:57 pm »

It's the calculator on some other designer's site I'm referring to... Yes, I agree that sabine calcs of empty rooms can seem long, but this java script seems very short to me..hmmmm??
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Francis Manzella - President, FM Design Ltd.
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