FHWA Traffic Noise Model Technical manual

This Technical Manual is for the Federal Highway Administration’s Traffic Noise Model (FHWA TNM®), Version 1.0 -- the FHWA’s computer program for highway traffic noise prediction and analysis. Two companion reports, a User’s Guide and a data report, respectively, describe the use of TNM and its vehicle noiseemissions data base. The Technical Manual documents the fundamental equations, the acoustical algorithms, and the interactive logic for all computations within TNM. Section 1 overviews the basic elements of TNM's prediction model. It describes the basic concepts of the model, from vehicle noise emissions to predicted sound levels. Section 2 describes TNM's prediction model in more detail, with references to the manual appendixes for detail on algorithms and mathematics. In particular, this section describes the following: (1) vehicle noise emissions for TNM's built-in vehicle types, (2) computation of vehicle speeds, when they are affected by upgrades and traffic-control devices, (3) geometrical complexity in the XY plane, plus computation of free-field sound levels from a roadway segment, (4) geometrical complexity in the vertical plane, along any line between roadway and receiver, plus the computation of attenuation relative to free field along any such line, (5) computation of parallel-barrier degradation for barriers or retaining walls that flank the roadway, and (6) computation of sound-level contours, insertion-loss contours, and level-difference contours. In addition, this manual contains detailed appendixes for each of these subjects.