Digital audio tape (DAT) is a type of media similar in appearance to the cassette tape. Introduced in 1987, the digital audio tape was designed to replace the cassette tape as the primary media for recording and playing audio. DAT is a digital medium, unlike cassettes, which are analog. Digital audio differs from analog audio in that instead of recording a continuous wavelength, digital audio records the analog wavelength of sound and converts it into a numeric equivalent for storage and playback.
Generally, digital audio is easier to edit than analog audio, as all points of sound are discrete and defined in time, unlike analog. While both analog and digital audio record the same sound, because of its storage mechanism, creating exact replicas of a digital recording is possible. Analog audio will often degrade over time as it is copied from one piece of media to another. Because DAT records in an uncompressed, digital format, exact replicas can be made from a DAT. This is not the case with other digital media formats that use compression.
Digital audio tape never gained a foothold in the consumer market, as it competed commercially against the compact disc (CD), and most major labels did not release music in the DAT format. It did gain popularity in professional and home audio recording, as it was the easiest way to create a master digital copy of many analog sources in the studio, or of a live recording. The digital audio tape standard allowed for four sampling modes: 32 kHz at 12 bits; and 32 kHz, 44.1 kHz, or 48 kHz at 16 bits. Adjusting the sampling rate allowed more or less audio information to be recorded onto the same tape.
Tapes came in lengths from 15 minutes to 180 minutes. Digital audio tape was also used for computer backups. A format was designed to be computer-specific, called Digital Data Storage (DDS). While computer tapes and audio tapes are a physically similar format, most DDS drives are incompatible with DAT audio tapes.
Digital audio tape has fallen out of favor in most recording environments as hard drive storage costs have decreased. Since hard drives allow for digital recording with virtually limitless length and quality, there no longer is an advantage to recording on digital audio tape. As such, there are few companies still producing DAT players and tapes, and many older recordings on DAT must be converted to newer formats or transferred to hard drives for storage.