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Author Topic: understanding room modes in non rectengular rooms  (Read 4755 times)

Constantin

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understanding room modes in non rectengular rooms
« on: April 13, 2009, 08:23:03 am »

Hi.  Smile

Since i am knocked out because of a "Sehenenscheidentz

Thomas Jouanjean

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Re: understanding room modes in non rectengular rooms
« Reply #1 on: April 13, 2009, 01:16:52 pm »

Those are big questions you're asking us to answer there, it's a long subject.

If your room is acoustically symetrical, then you'll have a symetrical response. There are no standard diagrams for cockpit rooms.

The rest will need a longer post. I'll give it a shot when I have some time.


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Thomas Jouanjean
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Constantin

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Re: understanding room modes in non rectengular rooms
« Reply #2 on: April 13, 2009, 02:36:09 pm »

edit: doublepost  Embarassed

Constantin

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Re: understanding room modes in non rectengular rooms
« Reply #3 on: April 13, 2009, 02:37:33 pm »

Thanks for reply Thomas  Smile

it would be great to learn more about these subject.
Maybe Francis is not as busy as you, and can give his point of view. Very Happy


cheers

Ethan Winer

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Re: understanding room modes in non rectengular rooms
« Reply #4 on: April 13, 2009, 03:49:29 pm »

I'm not Fran Laughing but one thing missing from those pressure graphs is the location of the sound source - the loudspeakers. That has a very large influence on where the peaks and nulls exist and how strong they are! Bear in mind that the response for any given point in a room is the sum of the modal response, plus peaks and nulls due to non-modal comb filtering from proximity of the speakers and the listener to room boundaries.

--Ethan

Constantin

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Re: understanding room modes in non rectengular rooms
« Reply #5 on: April 13, 2009, 04:10:25 pm »

Quote:

I'm not Fran

Yes, i Know you   Very Happy

http://xs138.xs.to/xs138/09161/ethan964.png

Very Happy  Shocked


I know what you want to say, but i`m intrested in only the modal acitivitys without SBIR, reflecions, ...........

For sure a mode has to be stimulated by a surce, but there are still some points were i can find a pressure maximum or minimum, which are caused only by roomdimensions, and shape.

cheers
Constantin

Ethan Winer

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Re: understanding room modes in non rectengular rooms
« Reply #6 on: April 14, 2009, 02:36:45 pm »

Wow, that's a nice pair of, er, diffusors!

Constantin wrote on Mon, 13 April 2009 16:10

i`m intrested in only the modal acitivitys without SBIR, reflecions


Okay, fair enough.

I'd love to invent a type of smoke like they use in dance clubs, but that would show sound pressure as different colors or whatever. Then you could play pink noise in a room and see where the peaks and nulls are located.

--Ethan

Thomas Jouanjean

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Re: understanding room modes in non rectengular rooms
« Reply #7 on: April 19, 2009, 07:55:57 am »

"are there any axial modes in a non rectangular room with no parallel surfaces?"

In short (I had no time to type anything):

Walls that aren't parallel do affect modal response, but they don't supress it. That would be nice though. But a good combination of geometry and treatment allows you to "clean up" the room and you can really redirect the energy where you want it to be. The complex modal response of these rooms is such that there is a "constant shift".

All those modes actually combine, whatever the room.

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Thomas Jouanjean
Northward Acoustics - Engineering and Designs
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Bruno Gouveia

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Re: understanding room modes in non rectengular rooms
« Reply #8 on: April 23, 2009, 01:52:24 pm »

Geometry is crucial not only for a better modal response, but also for the quality of reflections.

Any geometry that escapes much a shoe box shape it's going to get problems...

And no dead rooms please!

franman

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Re: understanding room modes in non rectengular rooms
« Reply #9 on: April 27, 2009, 10:52:12 pm »

There are axial modes in non-rectangular rooms...

Symmetrical room generally=symmetrical response....

Yes,  you could calculate the Axial mode front to back as you describe.....

SBI is equally in play with modal response. To ignore one is to ignore half of the picture.... just move around your small monitors in any room and see how much difference it makes!!

FM
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avare

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Re: understanding room modes in non rectengular rooms
« Reply #10 on: May 02, 2009, 02:14:48 pm »

Ethan Winer wrote on Mon, 13 April 2009 15:49

I'm not Fran Laughing but one thing missing from those pressure graphs is the location of the sound source - the loudspeakers.


It was in the corner.

Andre
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J.F.Oros

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Re: understanding room modes in non rectengular rooms
« Reply #11 on: May 06, 2009, 02:35:03 pm »

You can see what WSDG thinks about room modes in non rectangular rooms, in this movie, from their site :
http://old.wsdg.com/data/edithtml/resources/Files//clip-2008 -10-04%2012;00;14.wmv

It doesn't have naked chicks in it, but there are a lot of sexy studio pictures  Very Happy

By the way, you can also see there the software used by them to predict sound pressure maps inside this kind of rooms, a BEM tool that seems to be very interesting, if you can get over the very unfriendly interface. Bonus point, its a free software!
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Constantin

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Re: understanding room modes in non rectengular rooms
« Reply #12 on: May 06, 2009, 03:58:23 pm »

Hi Flaviu
Thanks for your reply  Smile
I cant watch this video since my internet connection is not made for download or streming big files (web and walk stick)

This Boundary Element methof sounds intressting, but i cant find a downloadsource for this freeware tool.
What is the  exact name of the tool, and do you know a downloadsource?

cheers
mika

J.F.Oros

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Re: understanding room modes in non rectengular rooms
« Reply #13 on: May 06, 2009, 06:34:12 pm »

Hi Mika

The software is called ABEC (http://www.randteam.de/Abec/Index.html) and its free for now because it's still in a testing stage.
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Constantin

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Re: understanding room modes in non rectengular rooms
« Reply #14 on: May 06, 2009, 08:21:01 pm »

Hey Smile
Thanks alot  Smile
I think i have something to read for the next days to understand this tool, but i think it will be a useful one.

good night
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