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Discussion on Acoustical Prediction Formulas of Road Sound Barrier
WANG Zuo-min
2012, 32 (3):
1-6.
DOI: 10.3969/j.issn.1006-1355.2012.03.001
There is some strict boundedness in acoustical prediction formulas of sound barrier recommended by some documents. The boundedness will limit applicable range of these formulas. Therefore some suggestion was proposed to improve acoustical prediction formulas of road sound barrier. The suggestion includes: (1) A universal method was introduced using the image source and image receiver when a reflect ground was considered; (2) Several corresponding prediction formulas were made when the source and receiver all are near a rigid ground, and for pulse point source, the attenuation formula was represented separately to express attenuation limiting value in an actual barrier when Fresnel number N>10; (3) The reflect sound reformation of a double barrier also can be calculated using the image source method.
The examples discussed in this paper not only prove that the suggestion is reasonable, but also provide some interested conclusion, such as (1) The reflect ground will increase sound pressure at a receiver, and decrease attenuation of barrier. When the source and receiver all are near a rigid ground, sound pressure at a receiver will increase 3 dB without a barrier, and 6 dB with a barrier, the attenuation of barrier will decrease 3 dB; (2) The reflect sound reformation of a double barrier almost are same with or without the reflect ground, and the reformation will decrease with increase of the absorption of barrier surface toward source.
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