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摘要
A highway noise prediction model which considers 20 s continuous equivalent sound level measure as the basic vehicular noise has been developed and is called the L-eq(20 s) model. The Leq(20 s) model is believed to provide accurate predictions by measuring the sound level of individual vehicle without assuming the vehicle noise source as a point source. To verify the rationality of L-eq(20 s) model, a mathematical derivation was performed based on the Federal Highway Administration (FHWA) traffic noise prediction model in this study. The derivation process indicated two defects in the L-eq(20 s) model. One was that given the lack of a revision item for finite length road, the L-eq(20 s) model cannot be applied to some special roads, such as in predicting the traffic noise level of a receiving point which is located at the tunnel portal of a highway. The other was that the L-eq(20 s) model had some theoretical deviations from the model of mathematical derivation from the FHWA model. When the speed of a vehicle ranged from 20 km/h to 120 km/h, the deviations ranged from 0.80 dB(A) to 0.13 dB(A). The deviations could be reduced if the constant item of -22.55 dB(A) in the L-eq(20 s) model was revised to 22 dB(A). To compare the accuracy of the L-eq(20 s) measure with the measure of the mean energy emission level, which was used as the basic vehicular noise in the FHWA model, a series of simultaneous measurements of a 5 s continuous equivalent sound level L-eq(5 s) and the maximum emission levels of individual vehicles was conducted. The measurements of L-eq(5 s) were compared with the calculations based on the hypothesis of monopole and dipole sources from the maximum emission levels of individual vehicles measured on roadsides. Result indicated that the mean value of measured L-eq(5 s) was close to that calculated from the maximum emission level with the hypothesis of monopole source for light vehicles. However, for medium and heavy vehicles, the mean value of measured L-eq(5 s) was between the two values calculated from the maximum emission level with the hypothesis of monopole and dipole sources. A mean error of 1.2-1.6 dB(A) was obtained for L-eq(5 s) when the mean energy emission level was employed in the FHWA model for medium and heavy vehicles. The accuracy of traffic noise prediction can be improved by considering L-eq(20 s) as the basic vehicular noise instead of the mean energy emission level.
- 出版日期2015-10
- 单位长安大学
