Quick REW question - why is smoothing necessary? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 02-23-2020, 07:00 AM - Thread Starter
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Quick REW question - why is smoothing necessary?

TLDR - one would expect an output LIKE after smoothing, but why is smoothing even needed? Why is the 'real result' so crazily noisy with literally 20dB differences between one frequency and the next>

Details:
Here is a few screenshots that I struggle with after measuring with REW/UMIK1 of a Ken Kreisel Q125:

nosmoothavg is the average of 3 recordings, but no smoothing.
It looks VERY fuzzy. zooming (to one actually, not to the curve) in is the 'screenshot' upload.
smoothavg is turning on the var smoothing on the average

After smoothing everything looks swell (and given that these are only sattelites, rated for 80-20,000 I'm not unhappy)

But why is smoothing necessary?

Why the noise?
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post #2 of 5 Old 02-23-2020, 03:05 PM
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Quote:
Originally Posted by puntloos View Post
TLDR - one would expect an output LIKE after smoothing, but why is smoothing even needed? Why is the 'real result' so crazily noisy with literally 20dB differences between one frequency and the next>
The sound from your speaker is bouncing off everything in the room, so what arrives at the microphone is the combination of the direct path plus the myriad reflections that arrive at various times shortly thereafter. They add constructively and destructively to cause variations in level at the mic. That's the "noise" in the data.

Smoothing helps mitigate those variations so you can see the underlying trend of the response more easily.

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post #3 of 5 Old 02-23-2020, 04:40 PM
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Smoothing makes it easier to read and easier to conceptualize.
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post #4 of 5 Old 02-24-2020, 01:31 AM
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It’s not “noise.” It’s what’s known as comb filtering, caused by (as Roger explained) the signal reaching the mic at different times, because of room reflections. A well-dampened room such as a recording studio will display minimal comb filtering, but it will be more prominent in a residential setting.

Smoothing (I like 1/3-octave) will get you a graph that looks more like what you’re actually hearing.

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Wayne A. Pflughaupt
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post #5 of 5 Old 02-24-2020, 02:35 AM
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I was wondering the exact same thing today when I was doing some measurements.
Thanks for the question and the responses
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