Investigating Alternative Representations of Building Structures in Traffic Noise Modeling

This paper presents the results of an investigation of various traffic noise modeling techniques with the Traffic Noise Model (TNM) 2.5 software package, with specific focus on the representation of traffic noise shielding from residences parallel to the freeway. A comprehensive traffic noise field study was undertaken in a neighborhood adjacent to Interstate 270 in Columbus, Ohio. Data collection activities occurred in three “waves” accounting for the pre-clearing, no barrier, and with barrier conditions. Measured noise levels at the study site indicated that there was some noise shielding effect of the residential structures; this effect was most readily perceptible behind the first row of residences. Separate TNM layouts were developed to represent the neighborhood’s residential structures as either a TNM building row object or as separate TNM barrier objects for each structure. The analysis found that modeling each individual residential structure as a separate TNM noise barrier object (single building façade that is closest to the freeway) produces the most accurate modeled noise levels, as compared to the building row representation or simply omitting the shielding from structures altogether. Based on these findings, it is recommended that traffic noise practitioners consider modeling each residential structure in noise-sensitive areas as TNM noise barrier objects.