Apple Final Cut Pro 6 - Manual (Page 804)

Chapter 1 Audio Fundamentals 19
I
Phase
Phase compares the timing between two similar sound waves. If two periodic sound
waves of the same frequency begin at the same time, the two waves are said to be
in phase. Phase is measured in degrees from 0 to 360, where 0 degrees means both
sounds are exactly in sync (in phase) and 180 degrees means both sounds are exactly
opposite (out of phase). When two sounds that are in phase are added together, the
combination makes an even stronger result. When two sounds that are out of phase
are added together, the opposing air pressures cancel each other out, resulting in little
or no sound. This is known as phase cancelation.
Phase cancelation can be a problem when mixing similar audio signals together, or
when original and reflected sound waves interact in a reflective room. For example,
when the left and right channels of a stereo mix are combined to create a mono mix,
the signals may suffer from phase cancelation.
In phase
Separate signals
Mixed signals
Out of phase