Hello there, I am trying to understand filters and have some questions. I’m using window 7, audacity 2.1.2 and used the .exe installer. I’ll preface this by saying I have little to no knowledge of either computer programming or signal processing.
So, as I understand it, this
(lp (hzosc 300) 50)
creates a barrier to any frequency over 50hz. When applied to the 300hz frequency, it lowers but does not silence the tone. Obviously, it is more of a band fade than a strict cut off. Is there any way to adjust how strict the cutoff is? Or how wide that band is? Some examples would be where the filter silences everything from 51hz and above? Or I set the range, so that a range setting of, say, 400hz would progressively quiet everything between 50hz and 450hz then produce silence on any tone over 450hz?
I experimented with higher order filters, and managed to get some response with the Q but nothing I understand. Like this
(highpass2 (hzosc 300) 500 600)
seems to add something, maybe resonance(?), then filter it away on a curve whose length is affected by the Q setting. Now I understand resonance and especially coefficients could be beyond my current comprehension levels, so I was happy that the even higher order filters didn’t have a Q setting.
It seemed to me that the higher the order, the more strict the cutoff setting became. With
(lowpass8 (hzosc 300) 200)
filtering much more than lowpass6 and even more than lowpass4. Now this alone would maybe be enough for me, however, I couldn’t get pwl to work with these.
(lp (hzosc 300) (pwl 0 50 .5 50 .55 1000 1 1000))
works fine but
(lowpass4 (hzosc 300) (pwl 0 50 .5 50 .55 1000 1 1000))
produces no sound. Is there a way to control the higher order filters with piece-wise approximations?
Last question. I can get this to work if I put the same filter on each individual osc but is there a way to apply one filter to all of these at once? I couldn’t figure out the syntax.
(sim (scale 0.2 (hzosc 220)) (scale 0.2 (hzosc 330)) (scale 0.2 (hzosc 440)))
I’d greatly appreciate any help or knowledge in understanding how these things work, but the three basic questions were:
1: Can you adjust specific cutoff settings?
2: Can you use piece-wise approximations on higher order filters?
3: Can you apply one filter on a group of simultaneous oscillators?