Physics: Difference between revisions - Bose Portable PA Knowledge

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:* As the cylindrical wave spreads out, the wave must expand over the surface of a cylinder. When the cylinder doubles in diameter, the small area of the sound wave at the closer distance must spread over a proportionately larger area at the doubled distance. As a result the intensity of the original area of sound wave is reduced. Since the area of a cylinder increases proportionately with only the radius (rather than as the square of the radius), increasing the distance from the source by a factor of two (doubling the radius) means reducing the sound intensity by only a factor of two.

:* As the plane wave progresses, the wave does not expand. When the wave reaches a distance that’s double the original, the small area of the sound wave at the closer distance hasn’t spread at all, and as a result the intensity of the original piece of sound wave is the same.

[[Image:SphericalCylindricalPlane.jpg|frame|center|A spherical-wave source, including virtually all existing loudspeakers, retains only one quarter of its intensity with each doubling of distance from the source. This is perceived as a rapid falloff of loudness with increasing distance. A cylindrical-wave retains half of its intensity with each doubling of distance from the source. This is perceived as a modest falloff of loudness with increasing distance. A plane-wave source loses no sound intensity with each doubling of distance from the source; in other words, the loudness is unchanged with increasing distance.]]

~~Figure x~~. A spherical-wave source, including virtually all existing loudspeakers, retains only one quarter of its intensity with each doubling of distance from the source. This is perceived as a rapid falloff of loudness with increasing distance. A cylindrical-wave retains half of its intensity with each doubling of distance from the source. This is perceived as a modest falloff of loudness with increasing distance. A plane-wave source loses no sound intensity with each doubling of distance from the source; in other words, the loudness is unchanged with increasing distance.

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 :* As the cylindrical wave spreads out, the wave must expand over the surface of a cylinder. When the cylinder doubles in diameter, the small area of the sound wave at the closer distance must spread over a proportionately larger area at the doubled distance. As a result the intensity of the original area of sound wave is reduced. Since the area of a cylinder increases proportionately with only the radius (rather than as the square of the radius), increasing the distance from the source by a factor of two (doubling the radius) means reducing the sound intensity by only a factor of two.
 :* As the plane wave progresses, the wave does not expand. When the wave reaches a distance that’s double the original, the small area of the sound wave at the closer distance hasn’t spread at all, and as a result the intensity of the original piece of sound wave is the same.
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+[[Image:SphericalCylindricalPlane.jpg|frame|center|A spherical-wave source, including virtually all existing loudspeakers, retains only one quarter of its intensity with each doubling of distance from the source. This is perceived as a rapid falloff of loudness with increasing distance. A cylindrical-wave retains half of its intensity with each doubling of distance from the source. This is perceived as a modest falloff of loudness with increasing distance. A plane-wave source loses no sound intensity with each doubling of distance from the source; in other words, the loudness is unchanged with increasing distance.]]
-Figure x. A spherical-wave source, including virtually all existing loudspeakers, retains only one quarter of its intensity with each doubling of distance from the source. This is perceived as a rapid falloff of loudness with increasing distance. A cylindrical-wave retains half of its intensity with each doubling of distance from the source. This is perceived as a modest falloff of loudness with increasing distance. A plane-wave source loses no sound intensity with each doubling of distance from the source; in other words, the loudness is unchanged with increasing distance.