Adobe AUDITION 1.5 - Manual (Page 275)

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Appendix B: Digital Audio
Primer
nderstanding the fundamentals of sound is the first step in learning about digital
audio. In this primer, we’ll introduce the basics of sound so you can work more
effectively with Adobe Audition and the rest of your digital audio or video toolkit.
Sound fundamentals
Sound is created by vibrations, such as those produced by a guitar string, vocal cords, or a
speaker cone. These vibrations move the air molecules near them, forcing molecules
together, and as a result raising the air pressure slightly. The air molecules that are under
pressure then push on the air molecules surrounding them, which push on the next set of
air molecules, and so forth, causing a wave of high pressure to move through the air. As
high pressure areas move through the air, they leave low pressure areas behind them.
When these pressure lows and highs—or waves—reach us, they vibrate the receptors in
our ears, and we hear the vibrations as sound.
When you see a visual waveform that represents audio, that waveform represents these
pressure waves. The zero line in the waveform is the pressure of air at rest. When the line
swings up, it represents higher pressure, and when it swings low, it represents lower
pressure. This waveform is the equivalent of the pressure waves in the air.
A sound wave represented as a visual waveform
A. Zero line B. Low pressure area C. High pressure area
U
B
A
C
0
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