SOUND-PROPAGATION THROUGH VEGETATION

The propagation of sound through a large number of scatters (i.e., trees) is treated in a smilar way to a classical diffusion problem. A general differential equation governing the sound intensity is derived which is valid under certain conditions, notably that the depth of the belt of vegetation is large and absorption small. The predictions of this theory are compared with results derived from a small scale model study and with some field measurements. They are compared with published field data. The implications of some of the conclusions reached for the practical achievement of effective sound attenuation are pointed out. Apparently, significant noise reductions may be achieved for a predominantly high frequency source of the existing ground cover is acoustically hard, or if there is no ground effect attenuation between source and receiver for some other reason. In other cases, the noise reduction will be much lower and may be negative.