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Public Address System
A public address system (or PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound source or recorded sound or music. PA systems are used in any public venue that requires that an announcer, performer, etc. be sufficiently audible at a distance or over a large area. Typical applications include sports stadiums, public transportation vehicles and facilities, and live or recorded music venues and events. A PA system may include multiple microphones or other sound sources, a mixing console to combine and modify multiple sources, and multiple amplifiers and loudspeakers for louder volume or wider distribution. Simple PA systems are often used in small venues such as school auditoriums, churches, and small bars. PA systems with many speakers are widely used to make announcements in public, institutional and commercial buildings ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Noise - Horn Loudspeakers At Brastad Soccer Arena
White is the lightness, lightest color and is achromatic (having no colorfulness, chroma). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully (or almost fully) diffuse reflection, reflect and scattering, scatter all the visible spectrum, visible wavelengths of light. White on television and computer screens is created by a mixture of red, blue, and green light. The color white can be given with white pigments, especially titanium dioxide. In ancient Egypt and ancient Rome, priestesses wore white as a symbol of purity, and Romans wore white togas as symbols of citizenship. In the Middle Ages and Renaissance a white unicorn symbolized chastity, and a white lamb sacrifice and purity. It was the royal color of the kings of France as well as the flag of Bourbon Restoration in France, monarchist France from 1815 to July Revolution, 1830, and of the White movement, monarchist movement that opposed the Bolsheviks during the Ru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Vacuum Tube Public Address System
Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican dancehall and reggae deejay Earlando Arrington Neil (1957–1994) * Early James, stage name of American singer-songwriter Fredrick Mullis Jr. (born 1993) * ''Early'' (Scritti Politti album), 2005 * ''Early'' (A Certain Ratio album), 2002 * Early Records, a record label Other uses * Early (name), a list of people and fictional characters with the given name or surname * Early effect, an effect in transistor physics * Early, a synonym for ''hotter'' in stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction gratin ... See also * * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Francisco City Hall
San Francisco City Hall is the seat of government for the City and County of San Francisco, California. Re-opened in 1915 in its open space area in the city's Civic Center, it is a Beaux-Arts monument to the City Beautiful movement that epitomized the high-minded American Renaissance of the 1880s to 1917. The structure's dome is taller than that of the United States Capitol by . The present building replaced an earlier City Hall that was destroyed during the 1906 earthquake, which was two blocks from the present one. The principal architect was Arthur Brown, Jr., of Bakewell & Brown, whose attention to the finishing details extended to the doorknobs and the typeface to be used in signage. Brown also designed the San Francisco War Memorial Opera House, Veterans Building, Temple Emanuel, Coit Tower and the Federal office building at 50 United Nations Plaza. __TOC__ Architecture The building's vast open space is more than and occupies two full city blocks. It is betw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Panama–Pacific International Exposition
The Panama–Pacific International Exposition was a world's fair held in San Francisco, California, United States, from February 20 to December 4, 1915. Its stated purpose was to celebrate the completion of the Panama Canal, but it was widely seen in the city as an opportunity to showcase its recovery from the 1906 San Francisco earthquake, 1906 earthquake. The fair was constructed on a site along the northern shore, between the Presidio of San Francisco, Presidio and Fort Mason, now known as the Marina District, San Francisco, Marina District. Planning Discussion of holding a World's Fair to celebrate the opening of the Panama Canal began in 1904. San Francisco, New Orleans, and San Diego, California promoted bids to be the site. Despite San Francisco ultimately getting the most support, San Diego went ahead with its own Panama–California Exposition. Exhibits and themes Among the exhibits at the exposition was the ''C. P. Huntington'', the first steam locomotive pur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phonograph
A phonograph, later called a gramophone, and since the 1940s a record player, or more recently a turntable, is a device for the mechanical and analogue reproduction of sound. The sound vibration Waveform, waveforms are recorded as corresponding physical deviations of a helical or spiral groove engraved, etched, incised, or impressed into the surface of a rotating cylinder or disc, called a ''Phonograph record, record''. To recreate the sound, the surface is similarly rotated while a playback #Stylus, stylus traces the groove and is therefore vibrated by it, faintly reproducing the recorded sound. In early acoustic phonographs, the stylus vibrated a Diaphragm (acoustics), diaphragm that produced sound waves coupled to the open air through a flaring Horn loudspeaker, horn, or directly to the listener's ears through stethoscope-type earphones. The phonograph was invented in 1877 by Thomas Edison; its use would rise the following year. Alexander Graham Bell's Volta Laboratory an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Feedback
Audio feedback (also known as acoustic feedback, simply as feedback) is a positive feedback situation that may occur when an acoustic path exists between an audio output (for example, a loudspeaker) and its audio input (for example, a microphone or guitar pickup). In this example, a signal received by the microphone is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the microphone again, amplified further, and then passed out through the loudspeaker again. The frequency of the resulting howl is determined by resonance frequencies in the microphone, amplifier, and loudspeaker, the acoustics of the room, the directional pick-up and emission patterns of the microphone and loudspeaker, and the distance between them. The principles of audio feedback were first discovered by Danish scientist Søren Absalon Larsen, hence it is also known as the Larsen effect. Feedback is almost always considered undesirable when it occurs with a si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Microphone
The carbon microphone, also known as carbon button microphone, button microphone, or carbon transmitter, is a type of microphone, a transducer that converts sound to an electrical audio signal. It consists of two metal plates separated by granules of carbon. One plate is very thin and faces toward the speaking person, acting as a diaphragm (acoustics), diaphragm. Sound waves striking the diaphragm cause it to vibrate, exerting a varying pressure on the granules, which in turn changes the electrical resistance between the plates. Higher pressure lowers the resistance as the granules are pushed closer together. A steady direct current is passed between the plates through the granules. The varying resistance results in a modulation of the current, creating a varying electric current that reproduces the varying pressure of the sound wave. In analogue telephony, this undulating current is directly passed through the telephone wires to a telephone exchange, and is routed to a reci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gauss (unit)
The gauss (symbol: , sometimes Gs) is a unit of measurement of magnetic induction, also known as magnetic flux density. The unit is part of the Gaussian units, Gaussian system of units, which inherited it from the older centimetre–gram–second system of units#Electromagnetic units .28EMU.29, centimetre–gram–second electromagnetic units (CGS-EMU) system. It was named after the German mathematician and physicist Carl Friedrich Gauss in 1936. One gauss is defined as one maxwell (unit), maxwell per square centimetre. As the centimetre–gram–second system of units (cgs system) has been superseded by the International System of Units (SI), the use of the gauss has been deprecated by the standards bodies, but is still regularly used in various subfields of science. The SI unit for magnetic flux density is the Tesla (unit), tesla (symbol T), which corresponds to . Name, symbol, and metric prefixes Although not a component of the International System of Units, the usage of the g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire (likely copper) wound into a electromagnetic coil, coil. A current through the wire creates a magnetic field which is concentrated along the center of the coil. The magnetic field disappears when the current is turned off. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and makes a more powerful magnet. The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be quickly changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet, which needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field. Electromagnets are widely used as components of other electrical devices, such as Electric motor, motor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horn (acoustic)
An acoustic horn or waveguide is a tapered sound guide designed to provide an acoustic impedance match between a sound source and free air. This has the effect of maximizing the efficiency with which sound waves from the particular source are transferred to the air. Conversely, a horn can be used at the receiving end to optimize the transfer of sound from the air to a receiver. Acoustic horns are found in nature in the form of the burrows constructed by male mole crickets to amplify their song. The earliest appearance of the horn in connection to sound in The Times was published in 1786: Applications Acoustic horns are used in: * horn loudspeakers * brass and woodwind musical instruments * vehicle horns such as those used on cars, trucks, trains, boats, and bicycles * megaphones, often used by lifeguards at public swimming pools. * foghorns, used to warn ships * ear horns, used by people who are hard of hearing (the human ear itself having the form of a horn) * pickup hor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diaphragm (acoustics)
In the field of acoustics, a diaphragm is a transducer intended to inter-convert mechanical vibrations to sounds, or vice versa. It is commonly constructed of a thin membrane or sheet of various materials, suspended at its edges. The varying air pressure of sound waves imparts mechanical vibrations to the diaphragm which can then be converted to some other type of signal; examples of this type of diaphragm are found in microphones and the human eardrum. Conversely a diaphragm vibrated by a source of energy beats against the air, creating sound waves. Examples of this type of diaphragm are loudspeaker cones and earphone diaphragms and are found in air horns. Loudspeaker In an electrodynamic loudspeaker, a diaphragm is the thin, semi-rigid membrane attached to the voice coil, which moves in a magnetic gap, vibrating the diaphragm, and producing sound. It can also be called a cone, though not all speaker diaphragms are cone-shaped. Diaphragms are also found in headphones. Qu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voice Coil
A voice coil (consisting of a former, collar, and winding) is the coil of wire attached to the apex of a loudspeaker cone. It provides the motive force to the cone by the reaction of a magnetic field to the current passing through it. The term is also used for voice coil linear motors such as those used to move the heads inside hard disk drives, which produce a larger force and move a longer distance but work on the same principle. In some applications, such as the operation of servo valves, electronic focus adjustment on digital cameras, these are known as voice coil motors (VCM). Operation By driving a current through the voice coil, a magnetic field is produced. This magnetic field causes the voice coil to react to the magnetic field from a permanent magnet fixed to the speaker's frame, thereby moving the cone of the speaker. By applying an audio waveform to the voice coil, the cone will reproduce the sound pressure waves, corresponding to the original input sig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
