Change Tempo noise

[SAJ]

Using 1.2.6 on XP SP2, I've noticed that sometimes when I use the Change Tempo effect, it creates a click or pop at the beginning or end of the selected region. I haven't been able to pin down what the occurrences had in common. I now try to set the end points in regions of silence (I've never seen it happen there), but that isn't always possible. Is this a bug? If so, is it fixed in 1.3? If not, if it's just a fact of life when editing digital recordings, what can I do to avoid it?

[alatham]

It's not a bug, it's a limitation of the way Audacity currently handles effects. What you're doing is creating a non-continuous waveform at the point that the editing starts (and stops). The reason you don't hear anything during silent parts is that the waveform is already floating around near zero, so any discontinuities will be just as quiet as the rest of the signal.

You have three options, either set the stop and start points during silent portions.

Or you can select the part you want and press "z" on your keyboard, this will shift the selection just a little bit to the nearest zero crossings, so the likelihood of any discontinuities is very small. Hopefully it won't shift the selection too far.

Finally, you can zoom way in and use the Pencil Tool to re-draw the waveform where the continuities appear (this doesn't always work well).