REW + UMIK-1 : RTA : erroneous low freq spectrum ?

RKwan

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Nov 30, 2017
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Newbie to this forum ... your enlighten is very much appreciated.

Just got my UMIK-1, and I am not sure why I get so much unexpected spectral reading on low freq ( < 30 Hz ) ?

The test the scenario, runs on a win10 desktop, with crappy speakers ( still betther than those on a laptop )
1) Run the REW tone generator : 1 KHz
2) UMIK-1 is about 4 feet from the speakers ( which are about 4 feet apart ).
3) Run SPL meter, and raise volume to 75dB
4) Run the REW RTA
5) Accumulated spectrum attached.

rew_1kh_7025317_asus.JPG


The RTA clear shows the 1KHz fundamental, and some line-frequency related noise.

What I don't understand is why are there so much energy at the low freq : < 30 Hz ?
- I don't have a sub woofer, thus don't expect much at the low end of the freq
- Can the UMIK-1 pick up at 2 Hz ?

The reason I want clarity on the low freq is that I would like to use REW + UMIK to characterize a hall : 88' x 50' x 30'.
Room of this size would have resonance freq in the single-digit-Hz.

Your enlightenment is much appreciated.
 
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