抄録
A series of measurements is made on a lawn field for sound propagation in two opposite directions. The average and the standard deviation are calculated from the field data in order to obtain the mean excess attenuation with nearly zero vector wind and the variation of sound level within a range of wind speed less than 3m/s. It is shown that the mean excess attenuation approximately agrees with a theoretically predicted value of ground attenuation, but by the effect of meteorological conditions the variation of sound level extremely increases with distance. The mean excess attenuation and the sound level variation are approximated by simple expressions with a parameter of a specific distance from which the attenuation and the variation start to increase. It is shown that the specific distance has a linear relation with a mean propagation height on a logarithmic scale. Numerical expression is given to the relation and an engineering model is obtained for the mean excess attenuation and the sound level variation. It is applicable to rough estimation of traffic noise propagation over absorptive ground like lawn.
