Instruction Manual

528 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.