A simple approximate expression for La of road traMc noise is explicitly fQrmulated on the basis of the analogous relation between an exponentially dis − tributed vehicles mode 正 and a one point source mode1 . Aone point sour ¢ e model assumes that only a point source is put on a lane in such a way that the situation of the source is determined statistically . An equivalent one point sQurce model is constructed by comparing the means , variances and the probability density functions of sound

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... ensity observed in both 皿 odels . The value of La in the one point source 皿 odel may be regarded as an apProximate value of La in the corresponding exponentially distributed vehicles mQdeL This method of approxima − tion is applied to the prediction of La in more realistic tra 伍 c flow models . The values of L α calculated from the derived equations and those from s 三 mulated calculation proved to be in good agreement