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Anechoic
An anechoic chamber (''an-echoic'' meaning "non-reflective") is a room designed to stop reflections of either sound or electromagnetic waves. They are also often isolated from energy entering from their surroundings. This combination means that a person or detector exclusively hears direct sounds (no reverberation, reflected sounds), in effect simulating being outside in a free field. Anechoic chambers, a term coined by American acoustics expert Leo Beranek, were initially exclusively used to refer to acoustic anechoic chambers. Recently, the term has been extended to other RF and Sonar anechoic chambers, which eliminate reflection and external noise caused by electromagnetic waves. Anechoic chambers range from small compartments the size of household microwave ovens to ones as large as aircraft hangars. The size of the chamber depends on the size of the objects and frequency ranges being tested. Acoustic anechoic chambers The requirement for what was subsequently called ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anechoic Chamber Dissipation
An anechoic chamber (''an-echoic'' meaning "non-reflective") is a room designed to stop reflections of either sound or electromagnetic waves. They are also often isolated from energy entering from their surroundings. This combination means that a person or detector exclusively hears direct sounds (no reflected sounds), in effect simulating being outside in a free field. Anechoic chambers, a term coined by American acoustics expert Leo Beranek, were initially exclusively used to refer to acoustic anechoic chambers. Recently, the term has been extended to other RF and Sonar anechoic chambers, which eliminate reflection and external noise caused by electromagnetic waves. Anechoic chambers range from small compartments the size of household microwave ovens to ones as large as aircraft hangars. The size of the chamber depends on the size of the objects and frequency ranges being tested. Acoustic anechoic chambers The requirement for what was subsequently called an anechoic c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radar Absorbent Material
In materials science, radiation-absorbent material, usually known as RAM, is a material which has been specially designed and shaped to absorb incident RF radiation (also known as non-ionising radiation), as effectively as possible, from as many incident directions as possible. The more effective the RAM, the lower the resulting level of reflected RF radiation. Many measurements in electromagnetic compatibility (EMC) and antenna radiation patterns require that spurious signals arising from the test setup, including reflections, are negligible to avoid the risk of causing measurement errors and ambiguities. Introduction One of the most effective types of RAM comprises arrays of pyramid shaped pieces, each of which is constructed from a suitably lossy material. To work effectively, all internal surfaces of the anechoic chamber must be entirely covered with RAM. Sections of RAM may be temporarily removed to install equipment but they must be replaced before performing any tes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Field (acoustics)
In acoustics, a free field is a situation or space in which no sound reflections occur. Characteristics The lack of reflections in a free field means that any sound in the field is entirely determined by a listener or microphone because it is received through the direct sound of the sound source. This makes the open field a direct sound field. In a free field, sound is attenuated with increased distance according to the inverse-square law. Examples and uses In nature, free field conditions occur only when sound reflections from the floor can be ignored, e.g. in new snow in a field, or approximately at good sound-absorbing floors (deciduous, dry sand, etc.) Free field conditions can be artificially produced in anechoic chambers. In particular, free field conditions play a major role in acoustic measurements and sound perception experiments as results are isolated from room reflections. With voice and sound recordings, one often seeks a condition free from sound reflection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loudspeaker
A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or "loudspeaker", comprises one or more such speaker ''drivers'', an enclosure, and electrical connections possibly including a crossover network. The speaker driver can be viewed as a linear motor attached to a diaphragm which couples that motor's movement to motion of air, that is, sound. An audio signal, typically from a microphone, recording, or radio broadcast, is amplified electronically to a power level capable of driving that motor in order to reproduce the sound corresponding to the original unamplified electronic signal. This is thus the opposite function to the microphone; indeed the ''dynamic speaker'' driver, by far the most common type, is a linear motor in the same basic configuration as the dynamic microphone which uses such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leo Beranek
Leo Leroy Beranek (September 15, 1914 – October 10, 2016) was an American acoustics expert, former MIT professor, and a founder and former president of Bolt, Beranek and Newman (now BBN Technologies). He authored ''Acoustics'', considered a classic textbook in this field, and its updated and extended version published in 2012 under the title ''Acoustics: Sound Fields and Transducers''. He was also an expert in the design and evaluation of concert halls and opera houses, and authored the classic textbook ''Music, Acoustics, and Architecture'', revised and extended in 2004 under the title ''Concert Halls and Opera Houses: Music, Acoustics, and Architecture''. Early life and education Beranek was born in 1914 in Solon, Iowa. His father Edward Fred Beranek was a farmer whose ancestors came from Bohemia (in what is now the Czech Republic) and his mother Beatrice Stahle, previously a schoolteacher, had become a farmwife. Edward's paternal grandparents Josef Beránek and Anna Ši ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Interference
Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data. Both man-made and natural sources generate changing electrical currents and voltages that can cause EMI: ignition systems, cellular network of mobile phones, lightning, solar flares, and auroras (northern/southern lights). EMI frequently affects AM radios. It can also affect mobile phones, FM radios, and televisions, as well as observations for radio astronomy and atmospheric science. EMI can be used intentionally for radio jamming, as in electronic warfare. History Since the earliest days of ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
40th Flight Test Squadron F-16 Fighting Falcon Sits In The Anechoic Chamber
4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures. In mathematics Four is the smallest composite number, its proper divisors being and . Four is the sum and product of two with itself: 2 + 2 = 4 = 2 x 2, the only number b such that a + a = b = a x a, which also makes four the smallest squared prime number p^. In Knuth's up-arrow notation, , and so forth, for any number of up arrows. By consequence, four is the only square one more than a prime number, specifically three. The sum of the first four prime numbers two + three + five + seven is the only sum of four consecutive prime numbers that yields an odd prime number, seventeen, which is the fourth super-prime. Four lies between the first proper pair of twin primes, three and five, which are the first two Fermat primes, like seventeen, which is the third. On the other hand, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies; these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range. Electric current Electric currents that oscillate at radio frequencies (RF currents) have special properties not shared by direct current or lower audio frequency alternating current, such as the 50 or 60 Hz current used in electrical power distribution. * Energy from RF currents in conductors can radiate into space as electromagnetic waves ( radio waves). This is the basis of radio technology. * RF current does not penetrate deeply into electrical c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna (radio)
In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic wave In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...s (radio waves). In Receiver (radio), reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be Amplifier, amplified. Antennas are essential components of all radio equipment. An antenna is an array of conductor (material), conductors (Driven element, elements), elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
360 Anechoic Chamber Salford University Uk '', 2001
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36 may refer to: * 36 (number), the natural number following 35 and preceding 37 * One of these years of Gregorian or Julian calendars: ** 36 BC, 1st century BCE ** AD 36, 1st century ** 1936, 20th century ** 2036, 21st century Arts and entertainment * ''36'' (TV series), an American sports documentary show * "36", a 2002 song by System of a Down from ''Steal This Album!'' * 36 Quai des Orfèvres (film), a 2004 French crime film * "Thirty Six", a song by Karma to Burn from the album ''Almost Heathen ''Almost Heathen'' is the third studio album by the stoner rock band Karma to Burn, released in 2001 via Spitfire Records. It was the last album released before their seven-year disbandment in 2002. The album was reissued in 2022 by Heavy Psych Sou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiation Pattern
In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: “Antenna Theory, Analysis and Design”, John Wiley & Sons, Inc., 2nd ed. 1982 David K Cheng: “Field and Wave Electromagnetics”, Addison-Wesley Publishing Company Inc., Edition 2, 1998. Edward C. Jordan & Keith G. Balmain; “Electromagnetic Waves and Radiating Systems” (2nd ed. 1968) Prentice-Hall. Particularly in the fields of fiber optics, lasers, and integrated optics, the term radiation pattern may also be used as a synonym for the near-field pattern or Fresnel pattern.Institute of Electrical and Electronics Engineers, “The IEEE standard dictionary of electrical and electronics terms”; 6th ed. New York, N.Y., Institute of Electrical and Electronics Engineers, c1997. IEEE Std 100-1996. d. Standards Coordinating Committee 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
