Audio Format

An audio format is a medium for storing sound and music. The term is applied to both the physical recording media and the recording formats of the audio content – in computer science it is often limited to the audio file format, but its wider use usually refers to the physical method used to store the data.

Music is recorded and distributed using a variety of audio formats, some of which store additional information.


[edit] Timeline of audio format developments
Year Media formats Recording formats
1877 Phonograph cylinder Mechanical analog; "hill-and-dale" grooves, vertical stylus motion
1883 Music roll Mechanical digital (automated musical instruments)
1895 Gramophone record Mechanical analog; lateral grooves, horizontal stylus motion
1898 Wire recording Analog; magnetization; no "bias"
1925 Electrical cut record Mechanical analog; electrically cut from amplified microphone signal, lateral grooves, horizontal stylus motion, discs at 7", 10", 12", most at 78 rpm
1930s Reel-to-Reel, Magnetic Tape Analog; magnetization; "bias" dramatically increases linearity/fidelity, tape speed at 30 ips, later 15 ips with NAB equalization; refined speeds: 7 1/2 ips, 3 3/4 ips, 1 7/8 ips
1930s Electrical transcriptions Mechanical analog; electrically cut from amplified microphone signal, high fidelity sound, lateral or vertical grooves, horizontal or vertical stylus motion, most discs 16" at 33 1/3 rpm
1948 (Commercial release) Vinyl Record Analog, with preemphasis and other equalization techniques (LP, RIAA); lateral grooves, horizontal stylus motion; discs at 7" (most 45 rpm), 10" and 12" (most 33 1/3 rpm)
1957 Stereophonic Vinyl Record Analog, with preemphasis and other equalization techniques. Combination lateral/vertical stylus motion with each channel encoded 45 degrees to the vertical.
1962 4-Track Analog, 1/4 inch wide tape, 3 3/4 inches/sec, endless loop cartridge.
1963 Compact Cassette Analog, with bias, preemphasis, 0.15 inch wide tape, 17/8 inches/sec. 1970: introduced Dolby noise reduction.
1965 8-Track Analog, 1/4 inch wide tape, 3 3/4 inches/sec, endless loop cartridge.
1969 Microcassette Analog, 1/8 inch wide tape, used generally for notetaking, mostly mono, some stereo. 2.4 cm/s or 1.2 cm/s.
1969 Minicassette Analog, 1/8 inch wide tape, used generally for notetaking, 1.2 cm/s
1970 Quadraphonic 8-Track (Q8) Analog, 1/4 inch wide tape, 3 3/4 inches/sec, 4 Channel Stereo, endless loop cartridge.
1971 Quadraphonic Vinyl Record (CD-4) (SQ Matrix)
1975 Betamax Digital Audio 'Dolby Stereo' cinema surround sound
1976 Elcaset
1978 Laserdisc
1982 Compact Disc (CD-DA) PCM
1985 Audio Interchange File Format (AIFF)
1985 Sound Designer (by Digidesign)
1987 Digital Audio Tape (DAT)
1991 MiniDisc (MD) ATRAC
1992 Digital Compact Cassette (DCC)
1992 WAVEform (WAV)
Dolby Digital surround cinema sound

1993 Digital Theatre System (DTS)
Sony Dynamic Digital Sound (SDDS)

1995 MP3
1997 DVD Dolby Digital
1997 DTS-CD DTS Audio
1999 DVD-Audio
1999 Super Audio CD (SACD)
1999 Windows Media Audio (WMA)
1999 The True Audio Lossless Codec (TTA)
2000 Free Lossless Audio Codec (FLAC)
2001 Advanced audio coding (AAC)
2002 Ogg Vorbis
2003 DualDisc
2004 Apple Lossless (ALE or ALAC)
2005 HD-DVD
2006 Blu-Ray