ZERO CROSSING POINT EDITS

Zero Crossing Point Edits in Soundtrack Pro
By Steve Martin

When working in the waveform editor in Soundtrack Pro, it is important to understand the concept of Zero Crossing Points. When performing audio edits such as cuts, you want to make sure your edits begin and end on a zero crossing points otherwise you will hear an audible click when you play back your sound. So that begs the question – what is a zero crossing point?

Look at any audio waveform in Final Cut or Soundtrack Pro. Zero crossing is the dead center point of the waveform at 0 dB on the horizontal axis. To make your edits sound “clean” your edits should happen directly on this axis.

A selection has already been made on this sound effect using the selection tool. At this zoom level, it’s hard to see if the selection starts at the zero crossing. If you zoom into the waveform using the zoom tool or pressing your up arrow key, you can clearly see the “peaks” of the waveform extending above and below the zero crossing axis.

Notice that the current selection’s in point (the darker green region) begins in the middle of a peak. Making a cut here would produce the unwanted click.

1. To ensure that the selection is made at the zero crossing, choose Adjust Selection to Zero Crossing from the Edit menu. You have a few options here. You can adjust the in point, the out point, or both the in and out point together (either inward or outward). Here, I’m choosing to adjust the in point to the left.

If you look at the adjusted selection in the wavefrom you will see that the in point is now sitting squarely at the zero crossing point. You will need to adjust the out point if necessary.

Keyboard Shortcuts

If you do a lot of audio editing, you’ll quickly find learning the keyboard shortcuts is well worth your time. Here are the my favorite ones.

Adjust Selection to Zero Crossing