A means of converting an analog sound wave or signal to digital form, improving the fidelity and sound quality of the recorded sound. A common example of digital audio is a conventional audio CD, in which music exists as numerical data converted (in a CD player) to analog signals for playback.
Digital audio is used in a variety of multimedia applications, and is captured by he process of sampling; in other words, a digitizing device or audio capture board records small bits of an analog signal at a certain rate, producing a digital approximation of the continuous sound wave. The sampling rate (or the number of times a second a sample is taken) and the resolution (or bit depth) affects the quality of the sound recorded. Both these factors also affect the file size. Sound can also be recorded in stereo or mono. The following chart indicates some common—as of this writing—sampling rates:
As you can tell, to record a standard three-and-a-half minute song at the highest sampling rate and resolution (44.1 KHz, 16-Bit stereo, also known as CD-quality and is the rate at which commercial CDs are recorded) would require 36.75 megabytes. Lower sampling rates and bit depths are used for various purposes in multimedia that do not require such high quality audio, such as brief sound effects. Most narration is recorded at least at 22.05 KHz. See also Compact Disc-Digital Audio. See also MIDI.