How to use effect on part of the track without introducing the crack/pop sound?

Question

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

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:

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:

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:

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?

Answer 1

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.

Answer 2

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.