Apple Soundtrack Pro 3 - Manual (Page 487)

This appendix discusses the broad topics of sound and digital audio in order to provide
some background information for using Soundtrack Pro.
This appendix covers the following:
• What Is Sound? (p. 487)
• Digital Audio (p. 497)
What Is Sound?
All sounds are vibrations traveling through the air as sound waves. Sound waves are
caused by the vibrations of objects and radiate outward from their source in all directions.
A vibrating object compresses the surrounding air molecules (squeezing them closer
together) and then rarefies them (pulling them farther apart). Although the fluctuations
in air pressure travel outward from the object, the air molecules themselves stay in the
same average position. As sound travels, it reflects off objects in its path, creating further
disturbances in the surrounding air. When these changes in air pressure vibrate your
eardrum, nerve signals are sent to your brain and are interpreted as sound.
Fundamentals of a Sound Wave
The simplest kind of sound wave is a sine wave. Pure sine waves rarely exist in the natural
world, but they are a useful place to start because all other sounds can be broken down
into combinations of sine waves. A sine wave clearly demonstrates the three fundamental
characteristics of a sound wave: frequency, amplitude, and phase.
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