7
USING SOUNDBOOTH CS4
Digital audio fundamentals
A single cycle at left; a complete, 20-Hz waveform at right
A.
Wavelength
B.
Degree of phase
C.
Amplitude
D.
One second
How sound waves interact
When two or more sound waves meet, they add to and subtract from each other. If their peaks and troughs are perfectly
in phase,
they reinforce each other, resulting in a waveform that has higher amplitude than either individual waveform.
In-phase waves reinforce each other.
If the peaks and troughs of two waveforms are perfectly
out of phase
, they cancel each other, resulting in no waveform
at all.
Out-of-phase waves cancel each other.
In most cases, however, waves are out of phase in varying amounts, resulting in a combined waveform that is more
complex than individual waveforms. A complex waveform that represents music, voice, noise, and other sounds, for
example, combines the waveforms from each sound.
Because of its unique physical structure, a single instrument can create extremely complex waves. That’s why a violin
and a trumpet sound different even when playing the same note.
Two simple waves combine to create a complex wave.
C
A
B
A
D
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Updated 15 July 2009