Pops in audio when cutting and pasting
I’m getting pops whenever I cut and paste any audio track. I read that the pops would not be there after mix down, but they are. Can anyone help me out?
Wes
Pops are caused by two different things. They can be cause by audio drop outs when your hard disk can’t keep up. This indeed is fixed usually with an offline mixdown. However, this is not your issue. You issue is becuase you are cutting and pasting audio without being mindful of zero crossings. Zero crossings are where the wave form crosses the Y axis. If you cut and paste with out thinking about the zero crossing, you will get clicks every time no matter the program you use. It’s just physics. If you are spicing tracks together back to back like a loop, you can drag the edges together. N-track will show a little purple circle where the parts meet. When the purple cirle is there, N track automatically compensates for bad zero crossings. Otherwise, you’ll want to create a very short fade in/out and the beginning and end of the file in a wav editor (like 5 or six samples is enough) to create artificial zero crossings.
As usual, Bubba’s on the mark but there’s one more trick I use to solve the problem when there’s a gap between the sections of a track.
Expand the view out to maximum horizontal and full screen for the track vertical. You will now be seeing the waveform completely stretched out. At the end of the track section you’ll see a little square. Move the end of the section so that the waveform ends in that little square. That’s the zero point. You shouldn’t have a click if you hit it right.
The only thing to add, is that if the end of your first section has the waveform at the zero crossing point heading negative-wards, then ensure that at the start of the next section, it is also heading negative-wards, (or vice versa).
That way you minimise the amplitudes of the partials that are generated by the sharp change in direction of the final waveform, (and that’s the “click” you hear).
Of course, if you have a good wave editor, you can apply a low pass filter just in the immediate vicinity of the cross-over point to ensure the transition is smooth.
I think n-track sort of does some of that automatically anyway, but it’s never a bad idea it help it out a wee bit. 
Ali
Thanks alot guys! I’ll give it a shot.
Wes
another strategy is to expand the view out horizontally as far as possible and draw a short volume fade in/out right at the start/end of the part. this is a trick acid does to avoid clicks. may or may not work for you. just thought i’d mention it.
later…
I do all of the above.
Another trick that I sometimes use is zooming in a lot and then actually having a slight space in between the 2 parts so that they don’t actually join.
Sometimes this will get rid of any noise and if it’s small enough and the sound on each side right then you don’t hear any gap.
Especially if there are other things going on in the mix.
It’s like your brain won’t notice there is a gap or just fills it in but if there is a pop it stands out.
Rich
Don’t let the purple box fool you. That is there when the parts are linked – no gaps and no overlap – but it doesn’t guarantee no pops and clicks. To solve that you’ll have to zoom all the way in experiment to find a splice point that doesn’t pop. It can be very difficult sometime. Overlapping and crossfading is suppose to be one way to avoid the problem, but I haven’t had much luck with for my purposes.
Right, phoo.
Also, it isn’t really important whether the waves start and stop at a zero crossing – that’s just a trick to help make it easier. But it’s neither necessary or sufficient.
What you want is a joint that looks relatively smooth (no jump in level, and no sharp angle) where the two parts meet. That means that the level needs to be close, and the angle (slope) needs to be close as well. Ali mentioned that the slopes have to have the same sign (both crossing going positive or both going negative) and that’s good but not close enough.
A gap of silence between the two also isn’t good enough. That only works if the two ends slope slowly enough to zero, or if the loundess of the track is low.
Despite all the concerns I’ve added above, I do splicing all the time and can usually do it very quickly. Just zoom all the way in, drag the end-handles (little squares) around, and find a place where the two waveforms can meet at the same level, without any sharp angles.
Note that vertical zoom is important, too – if the track is too skinny, you can have a big level jump and not see it (big enough to hear quite clearly). If the waveform is two or three inches tall (peak to peak) on your screen, then you should be able to easily see any level jump that would be audible.
One more caution. When dragging the end handles, if you end up with a purple “joint circle”, and you move the handle again, it will move the right-hand waveform. Usually (if you’re cutting/pasting correctly, keeping things lined up to the click), you don’t want this to happen. So, if you see that circle, drag the right-hand wave’s end handle right a bit first to unjoin them. I wish it didn’t do this!
Huh… Never knew that the purple circle was just a junction. I thought it actually created a zero crossing for you. Ya learn something new everyday.