Fundamentals of a sound wave – Apple Final Cut Pro 6 User Manual

Page 803

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18

Part I

Audio Mixing

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.

Frequency
Frequency is the rate, or number of times per second, that a sound wave cycles from
positive to negative to positive again. Frequency is measured in cycles per second or
hertz
(Hz). Humans have a range of hearing from 20 Hz (low) to 20,000 Hz (high).
Frequencies beyond this range exist, but they are inaudible to humans.

Amplitude
Amplitude (or intensity) refers to the strength of a sound wave, which the human ear
interprets as volume or loudness. People can detect a very wide range of volumes, from
the sound of a pin dropping in a quiet room to a loud rock concert. Because the range
of human hearing is so large, audio meters use a logarithmic scale (decibels) to make
the units of measurement more manageable.

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1 ms

Amplitude

Time

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