Apple Final Cut Pro 5 - Manual (Page 826)

Chapter 3 Audio Fundamentals 39
I
Phase cancellation 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 cancellation.
Frequency Spectrum of Sounds
With the exception of pure sine waves, which rarely exist in nature, sounds are made
up of many different frequency components vibrating at the same time. The particular
characteristics of a sound are the result of the unique combination of frequencies it
contains. Musical sounds usually have a fundamental frequency, or pitch, and additional
frequencies, called overtones, or harmonics, that are related to the fundamental
frequency. The lower the fundamental frequency, the lower the pitch of the sound. For
example, a 440 Hz piano note sounds lower than an 880 Hz piano note.
Sounds contain energy in different frequency ranges, or bands. If a sound has a lot of
low-frequency energy, it has a lot of bass. The 250–4000 Hz frequency band, where
humans hear best, is described as midrange. High-frequency energy beyond the
midrange is called treble, and this adds crispness or brilliance to a sound.
Note: Different manufacturers and mixing engineers define the ranges of these
frequency bands differently, so the numbers described above are approximate.
In phase Out of phase
Frequency
Bass
–
+
Mid High
Amplitude (dB)
20 200 1 kHz 5 kHz 20 kHz