Me and my noob questions

Hi I am making an effect for voice microphone. Hopefully I won’t be asking dumb questions that have already been answered, but I’ll try to google my questions first…

Currently I’m trying to figure out how to subtract one sound from another. I take audio from the mic in, and duplicate it (A and B). On B, I filter out all the high frequencies. Then, I want to subtract B from A so that A no longer has the frequencies that are in B (which also means B won’t have the frequencies in A)

I tried the simple expression: a - b, but it don’t sound like it’s doing what I want.

Hey! From what I understand you try to high-pass your signal? Why not simply using a high-pass filter? You could also use a filter with 2 outputs, LP and HP.

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Do you want to make a frequency splitter?

I’m not that good with filter stuff but as far as I know, if you subtract anything but a 1 pole filter, you won’t get what you expect from a frequency split.

I think Frequency splitting for multi band processing is usually done with separate high- and lowpass filters.

Keep in mind, Im just guessing this based on the results i goth while experimenting around with no education in this field.

Almost all filters introduce frequency dependent phase shifts into the audio they are processing. After passing through the low pass filter, signal B has had phase shifts introduced. When you subtract it from A these phase shifts introduce peaks and lows in the frequencies that result. You would be better off using a pair of filters or a multimode filter that has both a low-pass and high pass output.

This is a state variable filter design that has a low-pass, high pass, band pass and band reject (notch) output.
Screen Shot 2021-03-14 at 6.34.07 PM
SVF Model 1.audulus (23.7 KB)

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