Effects of turbulence on the attenuation of noise by barriers

Abstract

Although atmospheric turbulence influences many aspects of sound propagation outdoors, its effects have not previously been considered when predicting the attenuation of sound by barriers. We have measured traffic noise attenuated by a barrier alongside a highway with microphones positioned above an asphalt surface 15 and 30 m behind the barrier. The sound levels were analyzed to obtain the average sound levels per 13‐octave band. To obtain a better test of the influence of turbulence on diffraction an idealised experiment was also performed. A barrier 2.5 m high and 17 m long was erected on a flat asphalt surface. Sound levels from a point source were measured for various source and receiver positions. The two series of measurements are compared with simple diffraction theory currently used and show that sound levels behind the barrier are often greater than predicted at higher frequencies. [Work supported by NSERC grant to Carleton University.]