Discussion of 'Improving Traffic-Noise Model Insertion Loss Accuracy Based on Diffraction and Reflection Theories' by Ning Shu, Louis F. Cohn, Roswell A. Harris, and Teak K. Kim

摘要

The writer of these comments is the designer of the Traffic Noise Model (TNM) acoustics computational algorithms and a lead author of the technical documentation manual for the TNM (Menge et al. 1998).rnThe article being discussed asserts that the FHWA TNM diffraction calculation does not include the image source in the surface of the diffracting barrier. On the contrary, that reflection is included in the calculation. Eq. (18) in the article is copied from the TNM technical manual Eq. 30; however, that equation is a general one that does not make clear that two separate values for chi are computed for the real and image sources, chi+ and chi-. Fig. 61 in the technical manual shows the image source with the appropriate angle measured from the surface of the barrier, and text on page 90 of the manual (between Eqs. 33 and 34) reads "The angles phi and phi0 are measured in radians, referenced to the left side of the diffracting obstruction.