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Chapter 16. Multimedia > Audio Fundamentals

Audio Fundamentals

Sound is just quivering air—the faster the quiver, the higher the sound; the more violent the quiver, the louder the sound. Sound pitch, or frequency, is measured in units called hertz (abbreviated as Hz), and a thousand of those units are called a kilohertz (abbreviated as kHz). The best human ears can hear frequencies ranging from a low, throbbing 20 Hz to a squealing 20 kHz. Sound intensity is often measured in decibels, and the range from the softest sound to the loudest in any given recording is called the dynamic range.

Audio data stored on the Mac (or any other computer) usually contains the information needed to re-create both the frequency and the intensity of the sound in any given instance. Most simply, this means measuring the intensity of the sound at regular intervals (usually thousands of times a second) and recording the intensity as a number. Given the rate of measurements (the sampling rate) and the measurements themselves, your Mac can easily re-create the sound waves.


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