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#1 Posted : 13 February 2008 11:03:00(UTC)
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Posted By Bill01 While doing some work on Noise, I came across this; not seen it before. The rule says that if you double the distance from a noise source you get a 6db reduction, anyone familiar with this? Thanks.
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#2 Posted : 13 February 2008 11:07:00(UTC)
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Posted By AlB I know that rule of thumb is 3bd reduction every 5m distance from noise source (dependant on no wind, flat, level terrain and no obstructions.
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#3 Posted : 13 February 2008 11:10:00(UTC)
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Posted By Jane Blunt Point source, in the open air, yes. See http://www.barrhill.org....sics/NOISE%20CONTROL.htm Not generally applicable elsewhere, e.g. when sound can get reflected off walls, or when the sound source is large. Jane
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#4 Posted : 13 February 2008 11:24:00(UTC)
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Posted By Alan Hoskins It's the (in)famous inverse square law that also applies to illumination. Double the distance and you get a quarter of the level, hence the 6dB reduction. Alan
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#5 Posted : 13 February 2008 11:37:00(UTC)
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Posted By Paul Leadbetter The inverse square law only applies to a point source and it does not work if the source is large compared with the distance from it. Also, it does not work for an extended source, such as a noisy road, where the rule of thumb is that doubling the distance only gives a 3dB reduction. Paul
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#6 Posted : 13 February 2008 11:48:00(UTC)
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Posted By Alan Hoskins Thanks Paul, same for lighting of course, but Jane had already mentioned that. A
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