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Parabolic loudspeaker
A parabolic loudspeaker is a loudspeaker which seeks to focus its sound in coherent plane waves either by reflecting sound output from a speaker driver to a parabolic reflector aimed at the target audience, or by arraying drivers on a parabolic surface. The resulting beam of sound travels farther, with less dissipation in air, than horn loudspeakers, and can be more focused than line array loudspeakers allowing sound to be sent to isolated audience targets. The parabolic loudspeaker has been used for such diverse purposes as directing sound at faraway targets in performing arts centers and stadia, for industrial testing, for intimate listening at museum exhibits, and as a sonic weapon.
A parabolic loudspeaker can send sound farther than traditional loudspeaker designs. The focused waves of a parabolic loudspeaker tend to dissipate in air at about 3 dB SPL per doubling of distance, rather than the usual 6 dB of conventional loudspeakers.
In a parabolic reflecting loudspeaker, one or more speaker drivers are mounted at the focal point of a parabola, facing away from the audience, toward the parabolic surface. The sound is bounced off the parabolic dish and leaves the dish focused in plane waves. The lowest frequency that can be directed into a narrow beam is dependent on the size of the parabolic dish.[failed verification] A parabolic reflector type of loudspeaker must have a diameter twice that of the wavelength of the lowest desired frequency,[citation needed] so to obtain directional control of frequencies down to 20 Hz, the dish would have to be over 113 feet (34 m) wide.
Limitations of parabolic reflector loudspeakers include the fact that they are comparatively large and bulky, and also have a fixed beam width with no ability to broaden or narrow the coverage pattern without changing the curvature of the dish. Their beam width is wider for low frequencies than it is for high frequencies, so at the periphery of the coverage pattern there is a region of sound coverage that does not receive the full strength of the high frequencies. In addition, some frequencies are reflected more efficiently than others, so the frequency response is uneven unless audio signal processing correction is applied before the signal reaches the amplifier. The presence and placement of the speaker driver prevents the center of the parabolic dish from reflecting sound outward, as that sound would reflect back into the speaker driver itself. In some loudspeaker designs, a hole is cut at the center of the parabolic dish, or damping material placed, such that no sound is reflected directly at the speaker driver.
A loudspeaker can be constructed with multiple speaker drivers arrayed on the surface of a parabolic dish. This type of loudspeaker does not reflect sound—it aims sound directly at the audience. As in non-parabolic arrays of drivers, the signal going to each of the multiple drivers can be digitally delayed relative to its neighbors to achieve beam steering, and thus to adjust the aiming point or coverage pattern of the parabolic array without physically changing its position or curvature.
The expense of a multiple driver loudspeaker is typically higher than a reflector-type parabolic dish due to the increased number of speaker driver components and amplifier channels.
The first use of a parabolic reflector in directing sound energy as a weapon was the Luftkanone designed by the German military during World War II. Its purpose was to emit a focused pulse of sonic energy directed from the ground to aircraft overhead, and to knock the aircraft out of the sky. The system for creating a shock wave of sonic energy relied on the combustion of methane and oxygen, with a frequency range of 800–1500 pulses per second. The parabolic reflector was 3.2 metres (10.5 ft) in diameter. It failed as a weapon, primarily because its range was not sufficient.
Modern sonic weapons such as the Long Range Acoustic Device (LRAD) rely on multiple loudspeaker drivers for increased sound power, and may array them in a flat plane rather than on a parabolic surface. Such weapons do not use parabolic reflectors which necessarily limit the number of drivers—a large area of drivers aimed at the reflector would occlude the parabolic dish.
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Parabolic loudspeaker AI simulator
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Parabolic loudspeaker
A parabolic loudspeaker is a loudspeaker which seeks to focus its sound in coherent plane waves either by reflecting sound output from a speaker driver to a parabolic reflector aimed at the target audience, or by arraying drivers on a parabolic surface. The resulting beam of sound travels farther, with less dissipation in air, than horn loudspeakers, and can be more focused than line array loudspeakers allowing sound to be sent to isolated audience targets. The parabolic loudspeaker has been used for such diverse purposes as directing sound at faraway targets in performing arts centers and stadia, for industrial testing, for intimate listening at museum exhibits, and as a sonic weapon.
A parabolic loudspeaker can send sound farther than traditional loudspeaker designs. The focused waves of a parabolic loudspeaker tend to dissipate in air at about 3 dB SPL per doubling of distance, rather than the usual 6 dB of conventional loudspeakers.
In a parabolic reflecting loudspeaker, one or more speaker drivers are mounted at the focal point of a parabola, facing away from the audience, toward the parabolic surface. The sound is bounced off the parabolic dish and leaves the dish focused in plane waves. The lowest frequency that can be directed into a narrow beam is dependent on the size of the parabolic dish.[failed verification] A parabolic reflector type of loudspeaker must have a diameter twice that of the wavelength of the lowest desired frequency,[citation needed] so to obtain directional control of frequencies down to 20 Hz, the dish would have to be over 113 feet (34 m) wide.
Limitations of parabolic reflector loudspeakers include the fact that they are comparatively large and bulky, and also have a fixed beam width with no ability to broaden or narrow the coverage pattern without changing the curvature of the dish. Their beam width is wider for low frequencies than it is for high frequencies, so at the periphery of the coverage pattern there is a region of sound coverage that does not receive the full strength of the high frequencies. In addition, some frequencies are reflected more efficiently than others, so the frequency response is uneven unless audio signal processing correction is applied before the signal reaches the amplifier. The presence and placement of the speaker driver prevents the center of the parabolic dish from reflecting sound outward, as that sound would reflect back into the speaker driver itself. In some loudspeaker designs, a hole is cut at the center of the parabolic dish, or damping material placed, such that no sound is reflected directly at the speaker driver.
A loudspeaker can be constructed with multiple speaker drivers arrayed on the surface of a parabolic dish. This type of loudspeaker does not reflect sound—it aims sound directly at the audience. As in non-parabolic arrays of drivers, the signal going to each of the multiple drivers can be digitally delayed relative to its neighbors to achieve beam steering, and thus to adjust the aiming point or coverage pattern of the parabolic array without physically changing its position or curvature.
The expense of a multiple driver loudspeaker is typically higher than a reflector-type parabolic dish due to the increased number of speaker driver components and amplifier channels.
The first use of a parabolic reflector in directing sound energy as a weapon was the Luftkanone designed by the German military during World War II. Its purpose was to emit a focused pulse of sonic energy directed from the ground to aircraft overhead, and to knock the aircraft out of the sky. The system for creating a shock wave of sonic energy relied on the combustion of methane and oxygen, with a frequency range of 800–1500 pulses per second. The parabolic reflector was 3.2 metres (10.5 ft) in diameter. It failed as a weapon, primarily because its range was not sufficient.
Modern sonic weapons such as the Long Range Acoustic Device (LRAD) rely on multiple loudspeaker drivers for increased sound power, and may array them in a flat plane rather than on a parabolic surface. Such weapons do not use parabolic reflectors which necessarily limit the number of drivers—a large area of drivers aimed at the reflector would occlude the parabolic dish.