The prediction of façade effects from a point source above an impedance ground

Abstract

In many environmental noise prediction schemes, an empirical correction factor of 2.5 or 3.0 dB is normally added for the calculation of noise levels 1 meter in front of a reflecting façade. In this paper, theoretical and experimental studies have been conducted to examine the validity and accuracy of such approximations for a point source. The theoretical analysis involves the extension of the classical Weyl–van der Pol formula to include the effect of a reflecting façade. Experimental measurements have been conducted in an anechoic chamber to validate the theoretical predictions. It has been demonstrated that the simple empirical correction factor is adequate in cases for the assessment of the façade noise levels near the ground. However, this correction factor is not sufficient to predict the noise levels high above the ground. Some adjustments of the correction factor are required for a better estimation of sound fields in front of a reflecting façade above an impedance ground.