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Originally Posted by DanDan  The moving mic is intended to spatially average. If done correctly, with multiple locations and enough samples, and averaging, the result should be the same every time. Statistics. |
For absorption measuring the tests I've seen are run 100 times and averaged. This gives high accuracy, but not necessarily high repeatability. This is why they have to run so many tests! (I'm kidding - the microphone is moving, so of course each run varies.)
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individual sweeps at the same location, with nothing else changing, give different results. I can see that you have some difficulty believing this Ethan, but surely you have noticed the problems with ETF and achieving Decay measurements?
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I have gotten lousy data from ETF (and R+D) when measuring reverb, but that's because the software is buggy in that regard. Again, successive tests with REW do not have that problem. When I get a chance later I'll run five tests in a row in my large home studio, with the microphone way back in the middle of the room, and post the results here. Again, the issue is repeatability, not absolute accuracy for an RT60 measurement.
--Ethan