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Tape Bias
Tape bias is the term for two techniques, AC bias and DC bias, that improve the fidelity of analogue tape recorders. DC bias is the addition of direct current to the audio signal that is being recorded. AC bias is the addition of an inaudible high-frequency signal (generally from 40 to 150 kHz) to the audio signal. Most contemporary tape recorders use AC bias. When recording, magnetic tape has a nonlinear response as determined by its coercivity. Without bias, this response results in poor performance, especially at low signal levels. A recording signal that generates a magnetic field strength less than the tape's coercivity cannot magnetise the tape and produces little playback signal. Bias increases the signal quality of most audio recordings significantly by pushing the signal into more linear zones of the tape's magnetic transfer function. History Magnetic recording was proposed as early as 1878 by Oberlin Smith, who on 4 October 1878 filed, with the U.S. pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bell Telephone Laboratories
Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by multinational company Nokia. With headquarters located in Murray Hill, New Jersey, the company operates several laboratories in the United States and around the world. Researchers working at Bell Laboratories are credited with the development of radio astronomy, the transistor, the laser, the photovoltaic cell, the charge-coupled device (CCD), information theory, the Unix operating system, and the programming languages B, C, C++, S, SNOBOL, AWK, AMPL, and others. Nine Nobel Prizes have been awarded for work completed at Bell Laboratories. Bell Labs had its origin in the complex corporate organization of the Bell System telephone conglomerate. In the late 19th century, the laboratory began as the Western Electric Engineering Departmen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Storage
Sound recording and reproduction is the electrical, mechanical, electronic, or digital 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. Sound recording is the transcription of invisible vibrations in air onto a storage medium such as a phonograph disc. The process is reversed in sound reproduction, and the variations stored on the medium are transformed back into sound waves. Acoustic analog recording is achieved by a microphone diaphragm that senses changes in atmospheric pressure caused by acoustic sound waves and records them as a mechanical representation of the sound waves on a medium such as a phonograph record (in which a stylus cuts 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hysteresis
Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of the moment often form a loop or hysteresis curve, where there are different values of one variable depending on the direction of change of another variable. This history dependence is the basis of memory in a hard disk drive and the remanence that retains a record of the Earth's magnetic field magnitude in the past. Hysteresis occurs in ferromagnetic and ferroelectric materials, as well as in the deformation of rubber bands and shape-memory alloys and many other natural phenomena. In natural systems it is often associated with irreversible thermodynamic change such as phase transitions and with internal friction; and dissipation is a common side effect. Hysteresis can be found in physics, chemistry, engineering, biology, and econ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dither
Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and video data, and is often one of the last stages of mastering audio to a CD. A common use of dither is converting a grayscale image to black and white, such that the density of black dots in the new image approximates the average gray level in the original. Etymology The term ''dither'' was published in books on analog computation and hydraulically controlled guns shortly after World War II. Though he did not use the term ''dither'', the concept of dithering to reduce quantization patterns was first applied by Lawrence G. Roberts in his 1961 MIT master's thesis and 1962 article. By 1964 dither was being used in the modern sense described in this article. The technique was in use at least as early as 1915, though not under the name ''dither''. In digita ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barkhausen Effect
The Barkhausen effect is a name given to the noise in the magnetic output of a ferromagnet when the magnetizing force applied to it is changed. Discovered by German physicist Heinrich Barkhausen in 1919, it is caused by rapid changes of size of magnetic domains (similarly magnetically oriented atoms in ferromagnetic materials). Barkhausen's work in acoustics and magnetism led to the discovery, which became the main piece of experimental evidence supporting the domain theory of ferromagnetism proposed in 1906 by Pierre-Ernest Weiss. The Barkhausen effect is a series of sudden changes in the size and orientation of ferromagnetic domains, or microscopic clusters of aligned atomic magnets (spins), that occurs during a continuous process of magnetization or demagnetization. The Barkhausen effect offered direct evidence for the existence of ferromagnetic domains, which previously had been postulated theoretically. Heinrich Barkhausen discovered that a slow, smooth increase of a magne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Types Of Current
Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Type (Unix), a command in POSIX shells that gives information about commands. * Type safety, the extent to which a programming language discourages or prevents type errors. * Type system, defines a programming language's response to data types. Mathematics * Type (model theory) * Type theory, basis for the study of type systems * Arity or type, the number of operands a function takes * Type, any proposition or set in the intuitionistic type theory * Type, of an entire function ** Exponential type Biology * Type (biology), which fixes a scientific name to a taxon * Dog type, categorization by use or function of domestic dogs Lettering * Type is a design concept for lettering used in typography which helped bring about modern textual p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reichs-Rundfunk-Gesellschaft
The Reichs-Rundfunk-Gesellschaft (RRG; ''Reich Broadcasting Corporation'') was a national network of German regional public radio and television broadcasting companies active from 1925 until 1945. RRG's broadcasts were receivable in all parts of Germany and were used extensively for Nazi propaganda after 1933. Historical recordings of RRG broadcasts are today held by the German Broadcasting Archive. History The company was established in Berlin on 15 May 1925 with a start capital of 100,000 Reichsmark as an umbrella organisation by nine regional broadcasters – that is to say, all of the German radio stations other than the Deutsche Stunde in Bayern – serving the various states of the Weimar Republic. From 1926, a majority share was held by the state-owned Deutsche Reichspost authority, represented by RF engineer and Reichspostministerium official Hans Bredow as chairman in the rank of a ''Reichs-Rundfunk-Kommissar''. The logo of the RRG was designed by German graphic d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Walter Weber (engineer)
Walter Weber (26 March 1907 in Gelsenkirchen – 18 July 1944 in German-occupied Kościan) was a German pioneer of electromagnetic sound recording. From 1925 to 1927 he studied at the Oldenburg Academy of Engineering. From 1 May 1928 to 31 December 1930 he was an engineer at the central laboratory of Siemens & Halske AG in Berlin. There he met Hans-Joachim von Braunmühl. When he moved to the laboratory of the Reichs-Rundfunk-Gesellschaft The Reichs-Rundfunk-Gesellschaft (RRG; ''Reich Broadcasting Corporation'') was a national network of German regional public radio and television broadcasting companies active from 1925 until 1945. RRG's broadcasts were receivable in all parts o ..., he followed him there in 1931. On 2 November 1938, he defended his thesis ''Das Schallspektrum von Knallfunken und Knallpistolen mit einem Beitrag über Anwendungsmöglichkeiten in der elektroakustischen Meßtechnik''. (''The sound spectrum of spark transmitters and oscillators with a contribution ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marvin Camras
Marvin Camras (January 1, 1916 – June 23, 1995) was an electrical engineer and inventor who was widely influential in the field of magnetic recording. Camras built his first recording device, a wire recorder, in the 1930s for a cousin who was an aspiring opera singer named Willy. He also built Willy a telephone, due to the fact that he could not afford one, at the age of 8. Shortly afterwards he discovered that using magnetic tape made the process of splicing and storing recordings easier. Camras's work attracted the notice of his professors at what is now Illinois Institute of Technology (IIT) and was offered a position at Armour Research Foundation (which merged with Lewis Institute in 1940 to become IIT) to develop his work. Before and during World War II Camras' early wire recorders were used by the armed forces to train pilots. They were also used for disinformation purposes: battle sounds were recorded and amplified and the recordings placed where the D-Day invasion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Engineering Society
The Audio Engineering Society (AES) is a professional body for engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or products for audio, and persons working in audio content production. It also includes acousticians, audiologists, academics, and those in other disciplines related to audio. The AES is the only worldwide professional society devoted exclusively to audio technology. Established in 1948, the Society develops, reviews and publishes engineering standards for the audio and related media industries, and produces the AES Conventions, which are held twice a year alternating between Europe and the US. The AES and individual regional or national ''sections'' also hold ''AES Conferences'' on different topics during the year. History The idea of a society dedicated solely to audio engineering had been discussed for some time before the first meeting, but wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biasing
In electronics, biasing is the setting of DC (direct current) operating conditions (current and voltage) of an active device in an amplifier. Many electronic devices, such as diodes, transistors and vacuum tubes, whose function is processing time-varying ( AC) signals, also require a steady (DC) current or voltage at their terminals to operate correctly. This current or voltage is called ''bias''. The AC signal applied to them is superposed on this DC bias current or voltage. The operating point of a device, also known as bias point, quiescent point, or Q-point, is the DC voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied. A bias circuit is a portion of the device's circuit which supplies this steady current or voltage. Overview In electronics, 'biasing' usually refers to a fixed DC voltage or current applied to a terminal of an electronic component such as a diode, transistor or vacuum tube in a circui ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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