Apple Soundtrack Pro - Manual (Page 287)

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Audio Basics
You can create professional-sounding music projects in Soundtrack Pro without any
background or training in music. This chapter describes the basic audio and music
concepts you need to know to get started.
Basic Audio Concepts
In order to understand how you can work with audio files and use the controls, effects,
and envelopes included in Soundtrack Pro, it’s helpful to know some basic terms and
concepts about audio.
Sound Waves
What we hear as sounds are vibrations traveling through the air as sound waves. Sound
waves move through the air like ripples in a pond, radiating outward from the sound’s
source in a regular pattern of compression and rarefaction.
Frequency and Amplitude
The rate at which a sound wave repeats (the time between two peaks of the wave) is
called its frequency. Frequency is expressed in cycles per second, or Hertz (Hz). We hear
a sound’s frequency as being relatively high (like a flute, a child’s voice, or a train
whistle) or low (like a bass guitar, a man’s voice, or the rumble of a train on the tracks).
The range of frequencies audible to human beings is roughly 20 Hz–20 kilohertz (kHz).
The depth or intensity of a sound is called its amplitude, and is expressed in decibels
(dB). We hear amplitude as the volume or loudness of a sound. The range of audible
loudness is roughly 0–130 dB. Higher decibel levels are painful to human hearing.
Frequency
Amplitude Time