I have a sound effect (bell ring) and I would like to increase the speed at which it decays:

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The change I want is not linear though. I would only like to speed up the last two thirds of the sound's duration. I can use change tempo effect:

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But this causes an audible "crack" in the sound at the border of the selection, because the effect only processed the selected sound, so the waveform now doesn't fit together. Here's a close look:

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In the past, I already encountered this issue. I usually used the draw tool to manually change the waves so that they - more or less - fit together:

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Needless to say, this only helps sometimes and basically, I don't even know what exactly am I doing when editing sound like that.

I also tried to start the selection at the point where the wave goes through zero - that doesn't seem to help.

I tried to use the "Remove click" audacity effect - it only made things worse. I need to prevent the click from appearing in the first place.

What's the correct way to apply sound effects on part of the sound?

  • In this particular case, you might just want to fade out the last half of the effect using some kind of volume automation (not exactly sure what Audacity offers, look for "Fade out" somewhere).
    – Linuxios
    Apr 29, 2016 at 16:34
  • It has Fade out effect but that has the same flaw when used on selection. All effects in the effect menu seem to have this problem. Apr 29, 2016 at 17:03
  • 1
    Works fine for me on a crash sound. How exactly are you using Fade Out?
    – Linuxios
    Apr 29, 2016 at 17:10
  • Isn't there some kind of cross-fade tool? I'm a Pro Tools user, and that's all I would do, create a crossfade and make sure it's not phase shifting between regions. Is this possible in the program you are using?
    – Utopia
    Apr 29, 2016 at 19:32

2 Answers 2


It is a work around, but you could dupöicate the sound, tempo change the whole file and blend in and out both files to get a smooth transition.


The popping sound comes from the sudden jump in level at the transition. The zero-crossing selection is what you should do before applying the effect.

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