Non-focusing SurfacesAny time the surfaces of a room focus the sound which is reflected from them, they create spots of high intensity and other spots with low intensity. This is generally undesirable in an auditorium since you want a uniform, evenly dispersed sound to all listeners. Even large flat reflective surfaces are to be avoided because of the prominant reflection which will be produced. Parallel flat walls can produce a pattern of reflections known as a "flutter echo" as the sound waves travel back and forth between the surfaces. Such flutter echoes are often encountered in high school gymnasiums where there are parallel side walls and also a reflective floor and ceiling. Even dispersion is such an important contributer to good acoustics that it is sometimes desirable to use anti-focusing surfaces in a music making area. Older architecture often had columns, decorative sculpture and woodwork, and other dispersing surfaces. In modern architecture with its flat expanses, it is necessary to design in some anti-focusing properties.
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Index Auditorium acoustics | ||
HyperPhysics***** Sound | Go Back |
Focused ReflectionsClick on any of the geometries for further details.
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Index Auditorium acoustics | |||
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Elliptical EnclosureAn ellipse has two focus points. Sound projected in any direction from one focus point will travel to the other. Sound from any point will tend to be focused toward some point, so ellipses are certainly to be avoided for most acoustical purposes.
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Index Auditorium acoustics | ||
HyperPhysics***** Sound | Go Back |
Parabolic Surfaces
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Index Auditorium acoustics | ||||
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Rotunda EffectA popular practice at the U.S. Capitol building in Washington, D.C. is to send a friend to the far side of the capitol dome. Ordinary conversation can be if the speaker and listener are both close to the wall of the dome. Many buildings with dome-like rotundas exhibit this guided reflection phenomena.
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Index Auditorium acoustics | ||
HyperPhysics***** Sound | Go Back |
Anti-focusing Surfaces
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Index Auditorium acoustics | ||
HyperPhysics***** Sound | Go Back |