Modal Calculations in an Asymmetrical Room

Ok, round two: My bad, I just figured the rules would be as generic as any other forum. This, of course, is no one's fault but my own, but thank your pointing out the error. I would have just waited and assumed no one cared or that I was asking a question too stupid to be answered. I've been working on finding the answer to this one: how to calculate the modes in a room that isn't symmetrical. As the normal calculation relies on the length of the room, how does one calculate this with diagonal walls? Attached is a 3d sketchup of the room. Alright, follow up: The dimensions of the room are right but the wall on the lower side is not three ft. but 98 and 1/2 Inches. My bad, I just caught the error.

First resize your pict and edit your profile to Forum standards, see and read the stickies. :wink: and welcome BTW

Yup welcome to the forum... Without going into great detail the answer is: Average out dimensions of the room to calculate the modes in a room that isn't symmetrical OR test the room. A better answer is in the stickies, on the SAE sight or maybe on Ethan's Winners site. I can't remember where I read it. My "bet" is the best explanation calculating I read was from Ethan. Testing is also explained in many threads on this and other web sites. A little searching should find you a well worded answer. If you zone in on Ethan's writings OR buy Rod's book you be set. Sorry to answer your question with a search quest. Marc

Ponch wrote:

how does one calculate this with diagonal walls?

Is this a room that's already built, or a proposed design? If the room is already built, it doesn't matter what a mode calculation says because 1) mode predictions are never 100 percent accurate, and 2) there's nothing you can do about it anyway so just treat the room with as many bass traps as you can manage. Also, as Marc said, a common approach is to average the dimensions. Marc is also correct about measuring the room if it's already built. That's the only way to know what you really have. --Ethan

Thanks for the warm welcome. heh, I have to say at this point I'd never propose a room design like this one, its already built. However, I'll be graduating this year and its a part of my senior project so I need to gather, for the utter sake of gathering, any amount of information possible to prove I've been working, hence the somewhat ridiculous questions/test protocols I've had to ask and find.

Check BBC RD report on low frequency room response, part one. Sory I don'tt he URL handy. Andre

I realize this is late information, but... The only way to calculate mode distribution for a non rectangular room is to use finite element analysis type methods....there is no analytical solution to be had. There is software out there to do it...but it's not cheap. Cheers Kris

In addition to Kris: http://www.interdomain.net.au/~bodzio/ Also look at the PDF documents which are an interesting read.