Long before sound was first recorded, music was recorded—first by written notation, then also by mechanical devices (e.g., music boxes). Automatic music reproduction traces back as far as the 9th century, when the Banū Mūsā brothers invented the earliest known mechanical musical instrument, in this case a hydropowered organthatplayed interchangeable cylinders. According to Charles B. Fowler, this "...cylinder with raised pins on the surface remained the basic device to produce and reproduce music mechanically until the second half of the nineteenth century."[1][unreliable source?] The Banu Musa brothers also invented an automatic flute player, which appears to have been the first programmable machine.[2] According to Fowler, the automata were a robot band that performed "...more than fifty facial and body actions during each musical selection."[1] In the 14th century, Flanders introduced a mechanical bell-ringer controlled by a rotating cylinder. Similar designs appeared in barrel organs (15th century),musical clocks (1598), barrel pianos (1805), and musical boxes (ca.1800). The fairground organ, developed in 1892, used a system of accordion-folded punched cardboard books. The player piano, first demonstrated in 1876, used a punched paper scroll that could store an arbitrarily long piece of music. The most sophisticated of the piano rolls were "hand-played", meaning that the roll represented the actual performance of an individual, not just a transcription of the sheet music. This technology to record a live performance onto a piano roll was not developed until 1904. Piano rolls have been in continuous mass production since around 1898.[citation needed] A 1908 U.S. Supreme Court copyright case noted that, in 1902 alone, there were between 70,000 and 75,000 player pianos manufactured, and between 1,000,000 and 1,500,000 piano rolls produced.[3] The use of piano rolls began to decline in the 1920s although one type is still being made today.
Wednesday, March 11, 2015
Sound recording and reproduction
Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing,instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording. Acoustic analog recording is achieved by a small microphone diaphragm that can detect changes in atmospheric pressure (acoustic sound waves) and record them as a graphic representation of the sound waves on a medium such as a phonograph (in which a stylus senses grooves on a record). In magnetic tape recording, the sound waves vibrate the microphone diaphragm and are converted into a varying electric current, which is then converted to a varying magnetic field by an electromagnet, which makes a representation of the sound as magnetized areas on a plastic tape with a magnetic coating on it. Analog sound reproduction is the reverse process, with a bigger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Electronically generated sound waves may also be recorded directly from devices such as an electric guitar pickup or a synthesizer, without the use of acoustics in the recording process other than the need for musicians to hear how well they are playing during recording sessions.
Digital recording and reproduction converts the analog sound signal picked up by the microphone to a digital form by the process of digitization. This lets the audio data be stored and transmitted by a wider variety of media. Digital recording stores audio as a series of binary numbers representing samples of the amplitude of the audio signal at equal time intervals, at a sample rate high enough to convey all sounds capable of being heard. Digital recordings are considered higher quality than analog recordings not necessarily because they have higher fidelity (wider frequency response or dynamic range), but because the digital format can prevent much loss of quality found in analog recording due to noise and electromagnetic interference in playback, and mechanical deterioration or damage to the storage medium. A digital audio signal must be reconverted to analog form during playback before it is applied to a loudspeaker or earphones.
Digital Recording
The first digital audio recorders were reel-to-reel decks introduced by companies such as Denon (1972), Soundstream (1979) and Mitsubishi. They used a digital technology known as PCM recording. Within a few years, however, many studios were using devices that encoded the digital audio data into a standard video signal, which was then recorded on a U-matic or other videotape recorder, using the rotating-head technology that was standard for video. A similar technology was used for a consumer format, Digital Audio Tape (DAT) which used rotating heads on a narrow tape contained in a cassette. DAT records at sampling rates of 48 kHz or 44.1 kHz, the latter being the same rate used on compact discs. Bit depth is 16 bits, also the same as compact discs. DAT was a failure in the consumer-audio field (too expensive, too finicky, and crippled by anti-copying regulations), but it became popular in studios (particularly home studios) and radio stations. A failed digital tape recording system was the Digital Compact Cassette (DCC).
Within a few years after the introduction of digital recording, multitrack recorders (using stationary heads) were being produced for use in professional studios. In the early 1990s, relatively low-priced multitrack digital recorders were introduced for use in home studios; they returned to recording on videotape. The most notable of this type of recorder is the ADAT. Developed by Alesis and first released in 1991, the ADAT machine is capable of recording 8 tracks of digital audio onto a single S-VHS video cassette. The ADAT machine is still a very common fixture in professional and home studios around the world.
In the consumer market, tapes and gramophones were largely displaced by the compact disc (CD) and a lesser extent the minidisc. These recording media are fully digital and require complex electronics to play back.
Digital sound files can be stored on any computer storage medium. The development of the MP3 audio file format, and legal issues involved in copying such files, has driven most of the innovation in music distribution since their introduction in the late 1990s.
As hard disk capacities and computer CPU speeds increased at the end of the 1990s,hard disk recording became more popular. As of early 2005 hard disk recording takes two forms. One is the use of standard desktop or laptop computers, with adapters for encoding audio into two or many tracks of digital audio. These adapters can either be in-the-box soundcards or external devices, either connecting to in-box interface cards or connecting to the computer via USB or Firewire cables. The other common form of hard disk recording uses a dedicated recorder which contains analog-to-digital and digital-to-analog converters as well as one or two removable hard drives for data storage. Such recorders, packing 24 tracks in a few units of rack space, are actually single-purpose computers, which can in turn be connected to standard computers for editing.
Sound systems
| Year | Name | Number of films |
|---|---|---|
| 2002 | 12-Track Digital Sound | 40 |
| 1953 | 3 Channel Stereo | 51 |
| 1953 | 4-Track Stereo (CinemaScope) | 586 |
| 1955 | 6-Track Stereo (Todd-AO and compatibles) | 89 |
| 1955 | 70 mm 6-Track | 527 |
| 1934 | Afifa Ton-Kopie | 1 |
| 1950 | AGA Sound System | 7 |
| 1909 | Animatophone | 3 |
| 1928 | Aurofone | 1 |
| 1943 | B.A.F. Sound System | 2 |
| 1907 | Biophone | 2 |
| 1938 | Blue Seal Noiseless Recording | 1 |
| 1929 | Bristolphone | 2 |
| 2001 | Broadway Surround | 1 |
| 1909 | Cameraphone | 1 |
| 1921 | Case | 1 |
| 1990 | CDS | 11 |
| 1974 | Chace Surround | 8 |
| 1905 | Chronophone | 106 |
| 1910 | Chronomegaphone | 1 |
| 1990 | Cinema Digital Sound | 5 |
| 1907 | Cinematophone | 53 |
| 1904 | Cineophone | 2 |
| 1909 | Cinephone Lubin | 57 |
| 1952 | Cinerama 7-Track | 13 |
| 1911 | Cinephonograph | 1 |
| 1949 | Cinesound | 10 |
| 1908 | Cinophone | 2 |
| 1923 | De Forest Phonofilm | 213 |
| 2002 | Digitrac Digital Audio System | 12 |
| 1975 | Dolby | 12497 |
| 2012 | Dolby Atmos | ? |
| 1993 | Dolby Digital | 19652 |
| 1999 | Dolby Digital EX | 288 |
| 1985 | Dolby SR (Surround) | 5865 |
| 2010 | Dolby Surround 7.1 | 50 |
| 1993 | DTS | 3735 |
| 1996 | DTS 70 mm | 28 |
| 2001 | DTS-8 | 2 |
| 1999 | DTS-ES | 93 |
| 1994 | DTS-Stereo | 137 |
| 1996 | DX Stereo | 3 |
| 1940 | Fantasound | 1 |
| 1929 | Filmtone | 2 |
| 1998 | Full Range Recording System | 5 |
| 1920 | Gaumontphone | 1 |
| 1898 | Hollmann–Eaves | 1 |
| 1973 | IMAX 6-Track | 25 |
| 1933 | International Recording Engineers System | 2 |
| 1992 | Iwerks Digital Audio | 5 |
| 1894 | Kinetophone (Dickson) | 7 |
| 1889 | Kinetophone (Edison) | 1 |
| 1958 | Kinopanorama 9-Track | 6 |
| 1913 | Kinoplasticon | 12 |
| 1956 | Klangfilm Magnetocord | 3 |
| 1954 | Klangfilm-Stereocord | 3 |
| 1990 | LC-Concept Digital Sound | 22 |
| 1969 | Li-Westrex System | 1 |
| 1938 | Magnaphone Western Electric | 3 |
| 1962 | Magnetocord | 1 |
| 1988 | Matrix Surround | 24 |
| 1929 | Mono | 137936 |
| 1925 | Movietone | 20 |
| 1938 | Optiphone | 5 |
| 1964 | Ortiphone | 1 |
| 1907 | Oskar Messter | 1 |
| 1949 | Perspecta Stereo | 58 |
| 1933 | Phillips Sound | 3 |
| 1900 | Phono-Bio-Taleaux | 1 |
| 1900 | Phono-Cinema-Theatre | 7 |
| 1921 | Phono-Kinema | 11 |
| 1922 | Phonofilm | 248 |
| 1921 | Photokinema | 8 |
| 1925 | Photophone (RCA) | 3 |
| 1914 | Polyscope | 2 |
| 1936 | Pulvári System | 5 |
| 1970 | Quadrophonic | 3 |
| 1975 | Quintaphonic | 1 |
| 1987 | Sony Dynamic Digital Sound (SDDS) | 2005 |
| 1977 | Sensurround | 13 |
| 1992 | Servotron Stereo | 5 |
| 1896 | Silent | 95017 |
| 1985 | Sonics | 4 |
| 1996 | Sonics-DDP | 47 |
| 1994 | Sonix | 13 |
| 1928 | Sonora-Bristolphone | 1 |
| 1997 | Sound 360° | 2 |
| 1992 | Sound Trax Surround Stereo | 4 |
| 1995 | Soundelux | 1 |
| 1965 | Spectra-Stereo | 2 |
| 1972 | Stereo | 45374 |
| 1978 | Super Space Sound | 1 |
| 1929 | Synchrotone | 2 |
| 1939 | Synthetic | 4 |
| 1932 | Systemi A. Shorin | 2 |
| 1940 | Système Cottet | 3 |
| 1933 | Tagephone | 1 |
| 2005 | TMH Labs 10.2 Channel Sound | 1 |
| 1928 | Tobis (Tonbild Syndicat) | 80 |
| 1922 | Tri-Ergon Sound System 68 mm | 2 |
| 1982 | Ultra Stereo | 1007 |
| 1938 | Variray Blue Seal Recording | 3 |
| 1935 | Visatone | 3 |
| 1980 | Vistasonic | 2 |
| 1925 | Vitagraph | 3 |
| 1926 | Vitaphone | 356 |
| 1911 | Vivaphone | 1 |
| 1921 | Western Electric | 20 |
| 1925 | Westrex (Fox & Western Electric) | 5 |
| 1938 | Wicmar and Blue Seal Noiseless Recording | 1 |
Dolby Pro Logic
- By the late 1980s integrated-circuit manufacturers were working on designing integrated-circuit matrix decoders. A typical early example is the SSM-2125 from PMI.[10] The SSM-2125 is a complete Dolby Stereo matrix decoder (except for the surround delay) on a single chip, it allowed domestic decoders which used the same logic system found in professional decoders to be marketed to the consumer. These decoders were thus given the name "Dolby Pro-logic"
Dolby Surround
Dolby Surround' was the earliest consumer version of Dolby's multichannel analog film sound format Dolby Stereo.
Due to the compatibility of the Dolby Stereo matrix with mono and stereo playback, when films originally made in Dolby Stereo were released on stereo domestic video formats, such as VHS-HiFi or laserdisc, or broadcast on stereo TV the original two-channel Dolby Stereo soundtrack could be used. Some domestic listeners were keen to hear these soundtracks in a manner more akin to how they would have sounded in the theater and for that market some manufacturers produced simplified surround decoders. To keep the cost down these decoders dispensed with a center speaker output and the logic circuitry found on the professional decoder, but did include the surround delay. To distinguish these decoders from the professional units found in cinemas they were given the name "Dolby Surround" decoders. The term "Dolby Surround" was also licensed by Dolby for use on TV programs or straight-to-video movies recorded through the Dolby Stereo matrix.
Ultra Stereo
By 1984, Dolby Stereo had a competitor. Ultra Stereo Labs had introduced a comparable stereo optical sound system, Ultra Stereo. Its cinema processor introduced improvements in matrix decoding, with greater channel separation. An included balancing circuit compensated for film weave and some imbalances between the left and right tracks that previously caused voice leakage into the surround channel. The Ultra Stereo sound system won a 1984 Technical Achievement Award from the Academy of Motion Picture Arts and Sciences.
Dolby Stereo 70 mm Six Track
Dolby Stereo 70 mm Six Track refers to the use of Dolby noise reduction on the six magnetic soundtracks of a 70 mm print. This was first used on some prints of the MGM film Logan's Run released in 1976.
The Todd-AO format was introduced in 1955 and included multi-channel magnetic sound from the start, it does not have an optical soundtrack (although in recent years some 70mm prints have used a DTS digital track in place of the analogue magnetic one).
The original layout was for 5 front channels and one surround. But by the 1970s the use of the intermediate (left-center and right-center) tracks had been largely abandoned, these channels either being left blank, or filled with a simple mix of the adjacent channels. Dolby did not approve of this later practice, which results in loss of separation, but instead used these channels for LFE (low-frequency enhancement) utilizing the bass units of the otherwise redundant intermediate front speakers. Later the unused HF capacity of these channels was used to provide for stereo surround in place of the mono surround of the Todd-AO layout[8] giving the modern 5.1 channel allocation retained today by Dolby Digital.
The Dolby Stereo Matrix
The Dolby Stereo Matrix is straightforward: the four original channels: Left (L), Center (C), Right (R), and Surround (S), are combined into two, known as Left-total (LT) and Right-total (RT) by this formula:
| Dolby Stereo Mix | Left | Right | Center | Surround |
|---|---|---|---|---|
| Left Total |  |  |  |  |
| Right Total | | | |  |
where j = 90° phase-shift
This center channel information is carried by both LT and RT in phase, and surround channel information by both LT and RT but out of phase. This gives good compatibility with both mono playback, which reproduces L, C and R from the mono speaker with C at a level 3dB higher than L or R, but surround information cancels out. It also gives good compatibility with two-channel stereo playback where C is reproduced from both left and right speakers to form a phantom center and surround is reproduced from both speakers but in a diffuse manner.
A simple 4-channel decoder could simply send the sum signal (L+R) to the center speaker, and the difference signal (L-R) to the surrounds. But such a decoder would provide poor separation between adjacent speaker channels, thus anything intended for the center speaker would also reproduce from left and right speakers only 3dB below the level in the center speaker. Similarly anything intended for the left speaker would be reproduced from both the center and surround speakers, again only 3dB below the level in the left speaker. There is, however complete separation between left and right, and between center and surround channels.
To overcome this problem the cinema decoder uses so-called "logic" circuitry to improve the separation. The logic circuitry decides which speaker channel has the highest signal level and gives it priority, attenuating the signals fed to the adjacent channels. Because there already is complete separation between opposite channels there is no need to attenuate those, in effect the decoder switches between L and R priority and C and S priority. This places some limitations on mixing for Dolby Stereo and to ensure that sound mixers mixed soundtracks appropriately they would monitor the sound mix via a Dolby Stereo encoder and decoder in tandem.[7] In addition to the logic circuitry the surround channel is also fed via a delay, adjustable up to 100 ms to suit auditoria of differing sizes, to ensure that any leakage of program material intended for left or right speakers into the surround channel is always heard first from the intended speaker. This exploits the "Precedence effect" to localize the sound to the intended direction.
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