Hi David,
David F. Place wrote:
I heard some acoustical artifacts that I hadn't noticed when I was working in front of my computer listening through speakers. This extra "buzzing" sound is quite annoying. It's hard to imagine how my patches are making it. Does anyone have any wisdom about how to track down and fix these kind of problems? Are there any usual things you check first?
I know you said you checked what happens when you increase the sampling rate, but I would double check and make sure that what you are hearing isn't aliasing. I've found the difference between using an oversampled or otherwise bandwidth-limited oscillator and the normal [phasor~] or a square wave derived from [phasor~] and [expr~ $v1 > 0.5] to be the difference between day and night (or Stockhausen and Donkey Kong). Check 3.audio.examples/J07.oversampling.pd for one anti-aliasing strategy, or better yet compare a normal, ugly, aliased [phasor~] with the anti-aliased one in that example. List archives will turn up loads when you search for "bandwidth limited" as well.
Remember that once aliasing gets into a digital signal, no amount of filtering can remove it!
If aliasing isn't the problem, then you'd do best to tap a [dac~] into each section of your patch one by one and see where the problem is. I don't think anyone on this list is so psychic they can figure out it long-distance ;-)
Other things I would check, however, from experience:
- Any Amplitude Modulation, Frequency Modulation or other changes in
frequency or gain are done with audio signals, or via [pack 0 0] and [line~] with enough interpolation time set on the [pack] to get rid of any "stepping" or "zipper noise". 2) If you are using samples, that you haven't loaded such a large file into a table that the precision drops. You might have to go fishing in the archives to find out exactly how many samples it takes to do this, I can't remember offhand... 3) That you aren't clipping your final levels. Open the file up in a wave editor and see if the peaks hit 0dB. For some CD players even this is too hot, and you might want to aim for something more like -1dB or -3dB. Scout around on the internets for tips on mixing and mastering for CD to get an idea of where people tend to peak their levels.
best, Derek