Pops at edit points

I’m new to Audacity. Every time I do an edit, I get a pop. I use “Command X” and get a pop. When I cut and paste, I get a pop at the beginning and end of the new section. I just tried the “Change Pitch” effect for one note, and I get a pop at the beginning of the note and at the end of the note.
What am I doing wrong?

It’s almost certain you have one or more sound clips with “DC Offset.” Any time you edit between different clips, it’s going to pop or click. It really sends new users for a loop because if you edit between two clips from the same job, it mysteriously doesn’t do it.


The solution for old work is to Effect > Normalize > Remove DC (don’t let it do anything else) BEFORE you start editing. After you edit with damaged clips it’s too late past surgically removing the DC manually and that drives most people barking mad.

The long term solution is to fix the broken soundcard. Producing sound like that is not normal and as you’re finding, makes editing a nightmare and may cause other problems as well.


Try and make edits at “zero crossing points” (see here: http://manual.audacityteam.org/o/man/edit_menu.html#zero )

Write back when you find it. It’s my opinion that waveform cross is almost never serious and DC offset is far more likely to cause problems. DC will cause a robust pop or thunk in the show whereas a waveform cross error at best produces a very brief, tiny “tick” and if the show is loud enough, you just don’t hear it.

The top edit is bad. You would be able to hear this one because I used laboratory test tones, but for Trance or Electronica, it’s a waste of time.


Strictly speaking, that one’s not a zero crossing problem, that’s a waveform direction problem. You should try to match those, too. Zero Crossing would be joining the larger wave after it already started to rise.


Thanks so much for the replies. As to the sound card being bad, I’m using a 2 year old iMac, running 10.6.8. I will remember to run the “remove DC” before editing new stuff and hope that cures the problem. As to the “zero crossing points” edits, that is a tough one for me to understand at the moment. I need to study this more.

I did a quick test on a new file with the DC offset removed. I recorded myself with one note out of tune and in tune on the next measure. I copied the “good” note and pasted it over the “bad” note and got a pop at both ends of the edit. I also tried raising the pitch of the out of tune note by 1% and got pops at both ends. I would describe the pop as more of a tick but definitely noticeable. However, when I edit out a few silences, the ticks seem to be gone now. This is at least better than before.

If there are any other ideas, I would welcome them.

I’ll try to explain:
Here I have zoomed in very close on a recording and selected a tiny section.
If I delete this section it will produce a click at the edit point. Perhaps you can see, where the cursor line is, the waveform suddenly drops down to a different level - the waveform before the edit point does not match up with the waveform immediately after the edit point:
Now if I had made the selection slightly different, so that the selection starts and ends where the waveform crosses the centre “zero” line …
(here I pressed the “Z” key to make the selection snap to the zero crossing points)
Now when I delete the selection, the audio before the edit point matches up with the audio immediately after the edit point.

Clicks can usually be avoided at edit points by (1) correcting any DC offset before you start, and (2) choosing edit points carefully.

If I try to edit this selection, there is likely to be a click, pop or noticeable “discontinuity” at the start/end of the edited section.
By extending the selection a little I can make the audio to be edited start and end close to silence, so there is little chance of clicks at the start/end of the edit:

Always good practice to use Find Zero Crossings in my experience, unless it’s a very loud genre of music. Find Zero Crossings now works very well on mono tracks.


So each edit is an exercise in splitting the track into two monos and then recombining into stereo?

Video editors have no control over the edit point. They have to edit on television frame boundaries. They get around this by doing a very rapid dissolve at the cut point. Most people don’t notice that.

Saurnote should post a short WAV with one of the pops in the middle on the forum.



No. There is sometimes a problem finding zero crossing points on stereo tracks because zero crossing points may be in a different place on the left channel to the position in the right channel. Splitting a stereo track first will not help because you need the same selection in both channels, otherwise the channels will become out of synch.

The solution is to take care where edit points are positioned.
For cut/paste editing of mono tracks it is usually adequate to select zero crossing points (this usually works very well).
Other helpful techniques are to make the selection start and end at positions close to silence (which avoids clicks), or immediately on the onset of a strong beat (which hides clicks).
If none of these options are available, then the edit will need to be “fixed”, either by using the repair tool on the edit boundary, or editing a duplicate of the original and cross-fading from one to the other.

This was available as an option in Cool Edit Pro. It is a nice feature for “rough and ready” editing, but it is not suitable for very precise editing. Also it would be difficult to implement for anything other than Cut/Paste editing so the problem is likely to remain when glitches result from applying an effect to a selection.

A possible way round this would be to have an option/function to automatically apply “Repair” to edit points (to each end of the selection).
(this would be a “feature request” should you want to support it).

Here is a screen shot (if I’ve done it right). The pops are at about 6.50 and 7.20. I tried to raise the pitch of this note by 2%.
ScreenShot.tiff (164 KB)

Most web browsers do not display TIFF images, so I’ve converted it to a .PNG image.
That looks like a continuous sound with no gaps (silences) or beats to hide the “join”, which makes it tricky to apply effects that change the waveform without creating clicks.

What you will probably need to do is to duplicate the selection to a new track, apply the effect to the duplicate, then crossfade from the original to the duplicate and back again at the end.

A simpler method that may work (it’s difficult to tell just by looking) is that you may be able to use the Repair effect to smooth out the clicks http://manual.audacityteam.org/o/man/repair.html

OK I’ll support that… Find Zero Crossings seems tedious but doesn’t stop me recommending it as one of the tools for the job.


+1 I’d support that as a FR too.