Rational Acoustics

September 9th, 2009, 08:03 PM
Does anyone have any advice for getting good usable low frequency data in a dome situation with long decay times?

Arthur Skudra
September 9th, 2009, 08:24 PM
In the IR window, set your FFT size to the largest setting. Use a swept sine wave for stimulous. Perhaps increase the number of averages as well. And yes, this makes for a lengthy measurement time!

November 15th, 2009, 09:14 PM

As you heard from Arthur, use a LARGE FFT size. What you're doing there is taking alot of information into the computer before it makes any measurements. It's like sifting through more evidence before reaching a conclusion. View the resultant info with the ETC view, Energy vs Time. Phase information is disregarded and the peak is easier to spot. Then verify that your measurement is valid by looking at the TF with a phase view on. Flat phase in that area means you have achieved proper timing offset.


Arthur Skudra
November 15th, 2009, 10:03 PM
I should add that moving the measurement microphone around the room should reveal some interesting results...if you put the mic in the middle of the room, you will find significant low end buildup due to focusing effects of the concave surface. If you put your mic along the side wall, you potentially can find some interesting echo effects, dependent on the shape of the walls, especially if the stimulus source is also along the side wall.

Then you have a startling realization that such a room shape is the epitome of "achitorture"!!