Sound Wave Diffraction at the Edge of a Sound Barrier
J. Piechowicz
Department of Mechanics and Vibroacoustics, AGH - University of Science and Technology, al. A. Mickiewicza 30, 30-059 Kraków, Poland
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The diffraction phenomenon is described by the Huygens-Fresnel principle. The review of physical laws ruling the bending of sound waves at the edge of the screen allows the effective selection of both acoustical and geometrical parameters of the screen. Sound wave diffraction theories have been developed on the basis of wave optics, when wavelength is small in comparison to the size of the obstacles, which can be also used in acoustics with the same assumptions about geometry of the system. Diffraction can be seen as a result of the interference of waves reaching the point of observation in accordance with the laws of geometrical optics and wave disturbances arising as a result of interaction with the edge of an obstacle. The paper describes a test method using maximum length sequences for determining the intrinsic characteristics of sound diffraction in situ during testing of roadside noise barriers. A scale model experiment has been performed in an anechoic room. Also, a real noise reducing device was tested in free field conditions.
DOI: 10.12693/APhysPolA.119.1040
PACS numbers: 43.20.El, 43.20.Fn, 43.50.Gf, 43.50.Yw, 43.60.Ek, 43.55.Rg