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I'm using digital filters to apply spectral mangling-type special effects to audio.

When using a digital filter (vsts/standalone DSP programs/outboard digital filter, etc.), especially when using narrow transition bands/brickwall filters, are there any effective ways to remove ringing artifacts introduced by the filter? Please bear in mind I am new to DSP and my level of understanding is very basic.

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    $\begingroup$ The short answer is "don't make them brickwall filters". See here for the longer answer- dsp.stackexchange.com/questions/2170/… $\endgroup$ – Jim Clay Apr 26 '12 at 12:55
  • $\begingroup$ Can you hear the ringing? $\endgroup$ – endolith Apr 26 '12 at 16:52
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    $\begingroup$ @DaleNewton Yes, you could do the 180 degrees out of phase thing, but you would be changing the frequency response of the filter in such a way that it would no longer have a sharp transition. $\endgroup$ – Jim Clay Apr 27 '12 at 2:44
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    $\begingroup$ @DaleNewton Some sound examples would really help here. It's hard to tell at the moment whether what you're hearing is an artifact or the natural response of a narrow-band filter. $\endgroup$ – datageist♦ Apr 27 '12 at 2:45
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    $\begingroup$ @DaleNewton Probably not a solution to your problem, but I have some thoughts about ringing in this question: dsp.stackexchange.com/questions/6492/… $\endgroup$ – Mats Granvik Jan 12 '13 at 19:57
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Sticking with linear systems, removing the ringing is nearly the same as adding back some of the spectral content that your really steep transition filters removed. Why use some crazy scheme to add back the stuff in the "softer" transitions that your hard-edged filters cut out? Just use a more reasonable total filter response in the first place.

Going to non-linear systems, you could use some sort of AI pattern matching to determine what kind of sound waveforms would be perceived by a human a ringing, and just gate those waveforms out. But that might just add weird sounding artifacts of its own (as well as also spreading spectral content outside of your really steep filters).

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  • $\begingroup$ The narrow transition bands seem to be the only way to get some of the effects I'm after. The sound is often close to how Id like it, but the ringing is spoiling it. $\endgroup$ – Dale Newton Apr 27 '12 at 0:40
  • $\begingroup$ You might want to specify more precisely the audible result of the "effect you are after" in another new question, and see if it can be implemented without a bad filter. $\endgroup$ – hotpaw2 Apr 27 '12 at 0:49
  • $\begingroup$ Regarding your gating specific waveforms idea, I had no idea that was possible. Could you explain a little how that would be done? Would it be very different from how a regular filter works? Aside from my uses, If its possible to gate specific waveforms by some method other than that used by 'everyday' commercial Equalizers like I use (parametric filters / notch filters etc) I imagine such a filter could be very useful for many applications (removing mains hum, notch filtering, effects) etc. $\endgroup$ – Dale Newton Apr 27 '12 at 0:50
  • $\begingroup$ For example completely removing / augmenting specific frequencies or narrow bands of frequencies in order to change the spectral content / timbre of instruments. $\endgroup$ – Dale Newton Apr 27 '12 at 0:57
  • $\begingroup$ @Dale : if that was a question, you might want to ask it as a question, not make another comment under the current question. $\endgroup$ – hotpaw2 Apr 27 '12 at 13:54

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