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Posted to rec.audio.tech
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subtract one WAV file
wrote:
When I invert a WAV and mix it with itself, I don't get silence.
Anyone know why?
Sure.
Unless the inverted copy is EXACTLY in sync and EXACTLY the
same, sample-for-sample, you WON'T get silence.
From your original post:
"What is the easiest way to subtract one WAV file
from another? I want to compute the amount of
noise over a comm system."
Unless those two WAVE files are matched, time wise, to EXACTLY
the sample, then you won't get any cancellation.
If you're tlaking about taking a WAVE file and sending it over
a comm channel, recording it at the other side then comparing
the two by inverting one and summing, the difference you get
will be due to (in order of importance):
1. any time delay difference between the two,
2. Any gross gain difference between the two,
3. Any waveform distortion introduced by the comm channel
4. Any noise difference between the two.
Unless you're prepared to deal with #1, 2 and 3, you'll never
find any results due to #4.
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