Public address system facts for kids
A public address system, commonly known as a PA system, is a network of sound devices that can play sound to several people. They are often used to make announcements in large buildings or neighbourhoods. In big spaces outdoors, amplifiers and loudspeakers have to be very loud. Otherwise the volume would be too small to be heard by everybody.
Images for kids
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Horn loudspeakers are often used to broadcast sound in outdoor locations.
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A late 19th-century speaking trumpet used by firefighters
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A small sports megaphone for cheering at sporting events, next to a 3 in (8 cm) cigarette lighter for scale
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Early public-address system from around 1920 using a Magnavox speaker. The microphone had a metal reflector that concentrated the sound waves, allowing the speaker to stand back so it wouldn't obscure his or her face. The early vacuum tubes couldn't produce much gain, and even with six tubes the amplifier had low power. To produce enough volume, the system used a horn loudspeaker. The cylindrical driver unit under the horn contained the diaphragm, which the voice coil vibrated to produce sound through a flaring horn. It produced far more volume from a given amplifier than a cone speaker. Horns were used in virtually all early PA systems, and are still used in most systems, at least for the high-range tweeters.
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A woman using a small handheld electric megaphone at a demonstration in Portugal. Electric megaphones use a type of horn loudspeaker called a reflex or reentrant horn.
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Public address system consisting of amplifiers, mixers, and routers for a major international airport
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London Underground employee making a Long Line Public Address system announcement using an RPA01 Radio Microphone at Bank station
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This small venue's stage shows a typical PA system.
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A line array speaker system and subwoofer cabinets at a live music concert
See also
In Spanish: PA (electroacústica) para niños
