I am currently looking into solutions for Sound Classification, and I came across Ludvigsen's methodology (if anyone wishes to refer to it).
The problem is that a sample graph of amplitudes in one of his demos shows only positive amplitudes, while Sound Waves have both negative and positive amplitudes.
I have arrived to a point to know that positives are compression, while negative are rarefaction, but I still cannot quite comprehend the difference (and the importance of that difference) between the two.
- Would it, perhaps, make sense to handle only the absolute values (distance from zero) of either? Or would that lose properties defining a Sound Wave through rarefaction?
- Most importantly, how do some Software show Sound Waves (if they even are Sound Waves) with positive values only? Such as: Virtual DJ, most Equalizers.
PS: The values I am hoping to achieve are similar to the first figure on page 21 (Page 9 in the header) of this paper https://www.google.com.mt/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CDIQFjAC&url=https%3A%2F%2Fwww.uzh.ch%2Forl%2Fdiss_michael_buechler.pdf&ei=MaK6U43pIa3B7AbJgIHYCQ&usg=AFQjCNHqqOwIamFVMTul8h6f2z9J4fD2gA&bvm=bv.70138588,d.bGE&cad=rja .
I am still in progress of identifying what the Envelope Level (dB) axis represent.