Digital Audio is simply sound represented with numbers. It is categorized by an audio signal that is processed as binary data. Binary data is simply information stored in a format used by electronics (zeros and ones, positive/negitive, true/false, pits/platues, ...you get the idea). Examples of digital audio include Compact Discs, DATs, computer memory, and hard disk recorders. These mediums all use a binary system to represent an audio signal with numbers.

A digital audio recording is stored as a set of amplitude (volume) samplings. Each sample represents the amplitude of the audio signal at the time that it was recorded. Below is the same signal represented in both analog and digital forms. Each dot in the digital signal represents one sample.

Sample Rate - The amount of time between audio samples determines the quality of the reproduction. This is called the sample rate, that is the rate at which each sample is recorded. The sample rate is usually described in terms of cycles per second (Hertz/Hz) or thousands of cycles per second (Kilohertz/kHz). Compact Discs use a sample rate of 44.1 kHz, so it contains 44,100 samples for every second of digital audio. In fact, it is actually double that because CDs are in stereo so they must contain two channels of audio samples.

Sample Resolution - Another factor which influences the sound quality of a digital audio signal is the resolution. Sample resolution is also known as the bit-depth because it is determined by the number of bits used to represent one sample's amplitude. An 8-bit sample resolution provides relatively poor sound quality because it allows only 256 (2 to the 8th power) possible amplitude values for each sample. Samples with a very close amplitudes will be represented with the same value once recorded digitally. Standard audio CDs use a sample resolution of 16-bits which provides 65,536 (2 to the 16th power) possible values which will reproduce an audio signal more accurately than 8-bit.