Audio Digitization - Audio digitization is the conversion of analog audio sounds into digital form. To convert an analog audio signal to digital form, the analog signal is digitized by using an analog-to-digital (pronounced A to D) converter. The A/D converter periodically senses (samples) the level of the analog signal and creates a binary number or series of digital pulses that represent the level of the signal. The typical sampling rate for the conversion of analog audio ranges from 8,000 samples per second (for telephone quality) to 44,000 samples per second (for music quality).

Audio Compression - Audio compression is the analysis and processing of digital sound to a form that reduces the space required for transmission or storage. Audio compression coders and decoders (codecs) analyze digital audio signals to remove signal redundancies and sounds that cannot be heard by humans.

Digital audio data is random in nature unlike digital video which has repetitive information that occurs on adjacent image frames. This means that audio signals do not have a high amount of redundancy, making traditional data compression and prediction processes ineffective at compressing digital audio. It is possible to highly compress digital audio by removing sounds that can be heard or perceived by listeners through the process of perceptual coding.

Audio Coding - The type of coder (type of analysis and compression) can dramatically vary and different types of coders may perform better for different types of audio sounds (e.g. speech audio as compared to music).

The MPEG system allows for the use different types of audio coders. The type of coder that is selected can vary based on the application (such as playing music or speech) and the type of device the audio is being played through (such as a television or a battery operated portable media player). The MPEG speech coders range from low complexity (layer 1) to high complexity (layer 3). A new version of audio coder has been created (advanced audio codec-AAC) that offers better audio quality at lower bit rates. The AAC coder also has several variations that are used in different types of applications (e.g. broadcast radio -vs.- real time telephony).