Experimental Study on the Interaction Effect of Ground and Wind on Outdoor Sound Propagation

Abstract

Field measurements of sound propagating from a point source over a runway and a grass covered ground have been performed to examine the interaction effect of ground and wind on outdoor noise propagation. In the measurements, two loud speakers were used as sound sources radiating intermitted broad band noise and five receiving points were set in a straight line over a length of 300 m from each sound source. To compare the characteristic of sound propagation on the hard ground with that on the soft ground, the measurements on both grounds were made alternately. As a result, it was confirmed experimentally that the effect of wind on sound propagation depends on the acoustical property of the ground surface. As compared with the sound pressure levels under no-wind conditions, the increase in those under downwind conditions is large in the case of the soft ground, while the decrease under upwind conditions is large in the case of the hard ground. Moreover, the effectiveness of calculating the sound pressure level using the acoustic impedance obtained in the in-situ measurement was clarified.