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measuring in long reverb room
PostPosted: Tue Mar 23, 2010 8:00 pm Reply with quote
Jack
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Joined: 18 May 2008
Posts: 9




HI,I would like to measure polar data in a Gymnasium with long
reverb time (maybe 1 or 2 seconds I didn't measure yet) and would like
to know if this long reverb time will pollute my measurement and if
I have to get a measurement time longer than the reverb time for a
valid measurement and if it's the case,how long must be the measurement
time vs the reverb time.I will measure with easera standard and sweep
transfer measurement. Thanks
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PostPosted: Wed Mar 24, 2010 1:18 pm Reply with quote
Charlie
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Joined: 28 Apr 2005
Posts: 51
Location: Charlotte, NC USA




Hi Jack,
If I understand correctly you want to measure the polar (directivity) response of a loudspeaker in a gymnasium. The long reverb time of the gym will not pollute the measurements as long as you use a window on the measurements to eliminate not only the reverb but the first reflection from the closest surface. Usually this is from the floor.

The sweep time you will need for your measurement does not need to be any longer than the time when this first reflection arrives at the measurement mic. This is because all of the information in the impulse response arriving later than this time will be attenuated to zero by the window.

Hope this helps.

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Charlie Hughes
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PostPosted: Wed Mar 24, 2010 7:28 pm Reply with quote
Jack
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Joined: 18 May 2008
Posts: 9




You understand correctly Charlie ,I will measure at 10 feet high so
the ceiling is at 20 feets and the walls more than 40 feets apart
so I will measure with a window maybe a little less thans 10 ms so
I can be confident now that my measurement be valid to about 100hz.
thanks very much for your fast answer.
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measuring in long reverb room
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