Refers to the reproduction and transmission of sound stored in a digital format. This includes CDs as well as any sound files stored on a computer. In contrast, the telephone system (but not ISDN) is based on an analog representation of sound. In sound recording and reproduction systems, digital audio refers to a digital representation of the audio waveform for processing, storage or transmission. When analog sound waves are stored in digital form, each digital audio file can be decomposed into a series of samples.