Reference Guide

754
Editing audio
Digital audio fundamentals
The three waveforms shown above are quite different from one another, both in appearance and
sound. Each has its own characteristic shape, or envelope, and each has its own complex
combination of frequency components, which can change across the duration of the sound.
The center line of a waveform is the zero line; it corresponds to the rest position (displacement of 0)
of the original vibrating object. (A waveform for perfect silence would be a horizontal line at zero.)
Back and forth motions of the vibrating object translate to upward (positive) and downward
(negative) excursions of waveform amplitude. For example, a close-up of a portion of the guitar
waveform might look like this:
The waveform crosses the zero line twice during each complete vibration. These zero-crossings
are important in digital audio processing; they are good places to cut waveforms apart and splice
them together. If waveforms are cut or spliced at other locations, clicks and pops can occur. The
maximum amplitude of the waveform in each vibration is also important: it determines the strength of
the vibration, and thus the loudness of the sound.
See:
“Digital audio fundamentals” on page 750