Mathematical modeling of absorbent highway noise barriers

Abstract

Analytical modeling methods of complex noise barriers are presented in this paper. The models are developed by use of the geometrical theory of diffraction which allows for modeling of simple and complex shaped noise barriers. These models involve diffraction coefficients that include the influence of frequency, grazing angle, surface impedance and the source and receiver positions. The diffraction coefficients for complex shaped barriers are constructed from those for simple shapes by use of geometrical optics and physical acoustics. The influence of the ground on barrier diffraction is included through complex reflection coefficients for point sources off impedance covered planes. For highway noise barrier applications, the barrier noise reduction efficiency is calculated for a line of incoherent point sources. Scale model tests were conducted on barriers of various shapes. These include barriers shaped as thin walls, wedges, trapezoids with vertical or sloped walls and double thin walls. These barriers were tested with hard or absorbent surfaces erected over hard or absorbent ground.