Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, samples are taken 44,100 times per second, each with 16-bit sample depth. Digital audio is also the name for the entire technology of sound recording and reproduction using audio signals that have been encoded in digital form. Following significant advances in digital audio technology during the 1970s and 1980s, it gradually replaced analog audio technology in many areas of audio engineering, record production and telecommunications in the 1990s and 2000s.
Jack St. Clair Kilby was an American electrical engineer who took part, along with Robert Noyce of Fairchild Semiconductor, in the realization of the first integrated circuit while working at Texas Instruments (TI) in 1958. He was awarded the Nobel Prize in Physics on 10 December 2000.
Digital Audio Tape is a signal recording and playback medium developed by Sony and introduced in 1987. In appearance it is similar to a Compact Cassette, using 3.81 mm / 0.15" magnetic tape enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. The recording is digital rather than analog. DAT can record at sampling rates equal to, as well as higher and lower than a CD at 16 bits quantization. If a comparable digital source is copied without returning to the analogue domain, then the DAT will produce an exact clone, unlike other digital media such as Digital Compact Cassette or non-Hi-MD MiniDisc, both of which use a lossy data-reduction system.
A digital audio workstation is an electronic device or application software used for recording, editing and producing audio files. DAWs come in a wide variety of configurations from a single software program on a laptop, to an integrated stand-alone unit, all the way to a highly complex configuration of numerous components controlled by a central computer. Regardless of configuration, modern DAWs have a central interface that allows the user to alter and mix multiple recordings and tracks into a final produced piece.
Ray Milton Dolby Hon OBE, HonFREng was an American engineer and inventor of the noise reduction system known as Dolby NR. He helped develop the video tape recorder while at Ampex and was the founder of Dolby Laboratories.
In digital recording, an audio or video signal is converted into a stream of discrete numbers representing the changes over time in air pressure for audio, or chroma and luminance values for video. This number stream is saved to a storage device. To play back a digital recording, the numbers are retrieved and converted back into their original analog audio or video forms so that they can be heard or seen.
The Digital Audio Stationary Head or DASH standard is a reel-to-reel, digital audio tape format introduced by Sony in early 1982 for high-quality multitrack studio recording and mastering, as an alternative to analog recording methods. DASH is capable of recording two channels of audio on a quarter-inch tape, and 24 or 48 tracks on 1⁄2-inch-wide (13 mm) tape on open reels of up to 14 inches. The data is recorded on the tape linearly, with a stationary recording head, as opposed to the DAT format, where data is recorded helically with a rotating head, in the same manner as a VCR. The audio data is encoded as linear PCM and boasts strong cyclic redundancy check (CRC) error correction, allowing the tape to be physically edited with a razor blade as analog tape would, e.g. by cutting and splicing, and played back with no loss of signal. In a two-track DASH recorder, the digital data is recorded onto the tape across nine data tracks: eight for the digital audio data and one for the CRC data; there is also provision for two linear analog cue tracks and one additional linear analog track dedicated to recording time code.
Kornelis Antonie "Kees" Schouhamer Immink is a Dutch engineer, inventor, and entrepreneur, who pioneered and advanced the era of digital audio, video, and data recording, including popular digital media such as compact disc (CD), DVD and Blu-ray disc. He has been a prolific and influential engineer, who holds more than 1100 U.S. and international patents. A large portion of the commonly used audio and video playback and recording devices use technologies based on his work. His contributions to coding systems assisted the digital video and audio revolution, by enabling reliable data storage at information densities previously unattainable.
Soundstream Inc. was the first United States audiophile digital audio recording company, providing commercial services for recording and computer-based editing.
Robert B. Ingebretsen was a pioneer in the development of digital sound.
Audio recordings of conversations between U.S. President Richard Nixon and Nixon administration officials, Nixon family members, and White House staff surfaced during the Watergate scandal in 1973 and 1974, leading to Nixon's resignation.
James H. McClellan is the Byers Professor of Signal Processing at the Georgia Institute of Technology. He is widely known for his creation of the McClellan transform and for his co-authorship of the Parks–McClellan filter design algorithm.
Thomas Shi-Tao Huang was a Chinese-born American computer scientist, electrical engineer, and writer. He was a researcher and professor emeritus at the University of Illinois at Urbana-Champaign (UIUC). Huang was one of the leading figures in computer vision, pattern recognition and human computer interaction.
Alan Victor Oppenheim is a professor of engineering at MIT's Department of Electrical Engineering and Computer Science. He is also a principal investigator in MIT's Research Laboratory of Electronics (RLE), at the Digital Signal Processing Group.
The history of sound recording - which has progressed in waves, driven by the invention and commercial introduction of new technologies — can be roughly divided into four main periods:
Expensive Tape Recorder is a digital audio program written by David Gross while a student at the Massachusetts Institute of Technology. Gross developed the idea with Alan Kotok, a fellow member of the Tech Model Railroad Club. The recorder and playback system ran in the late 1950s or early 1960s on MIT's TX-0 computer on loan from Lincoln Laboratory.
Arun N. Netravali is an Indian–American computer engineer credited with contributions in digital technology including HDTV. He conducted research in digital compression, signal processing and other fields. Netravali was the ninth President of Bell Laboratories and has served as Lucent's Chief Technology Officer and Chief Network Architect. He received his undergraduate degree from IIT Bombay, India, and an M.S. and a Ph.D. from Rice University in Houston, Texas, all in electrical engineering. Several global universities, including the Ecole Polytechnique Federale in Lausanne, Switzerland, have honored him with honorary doctorates.
John Gould "Jay" McKnight was an American businessman and engineer who was the co-founder of the Magnetic Reference Laboratory, where he was engineering vice-president from 1972 to 1975 and was the president since 1975. He also developed new products and directed engineering at MRL.
Stellavox is a company based in Switzerland best known for its compact portable reel-to-reel magnetic tape audio recorders of extremely high mechanical quality, used by radio and TV-stations and motion picture location sound mixers as an alternative to the Nagra recorders. The company, founded in 1955 by Georges Quellet, was developing and manufacturing full size studio recording decks such as the Stellavox TD9 as well, which is still considered one of the best tape recorders ever made and has become a legend. Due to the high price, which was caused by the complexity of the technical solution and the precision of hand-made Swiss production, only a few hundred pieces were produced.
Robert E Fontana is an engineer, physicist, and author who is noted for his contributions in the areas of magnetic recording and data storage on hard disk drives (HDD) and on digital tape recorders. His work has concentrated on developing thin film processing techniques for nano-fabrication of magnetic devices including Giant Magnetoresistance read heads now used universally in magnetic recording. Much of his career was with IBM in San Jose, California. He is a Fellow of the Institute of Electrical and Electronics Engineers and a member of the National Academy of Engineering.
