Understanding digital audio

You hear sounds because your ear recognizes the variations in air pressure that create them. Analog audio reproduces sound variations by creating or reading variations in an electrical signal. Digital audio reproduces sound by sampling the sound pressure or signal level at a specified rate and converting that to a number.

The quality of digital audio depends on the sample rate and bit depth. The sample rate is how often the audio level is digitized. A 44.1 kHz sample rate is audio-CD quality, while CD-ROM or Internet audio often uses a sample rate of 22 kHz or below. The bit depth is the range of numbers used to describe an audio sample; 16 bits is audio-CD quality. Lower bit depths and sample rates are not suitable for high-fidelity audio, but may be acceptable (though noisy) for dialogue. The file size of an audio clip increases or decreases as you increase or decrease the sample rate or bit depth.