HIGHWAY TRAFFIC NOISE MEASUREMENTS AT ACOUSTICALLY HARD GROUND SITES COMPARED TO PREDICTIONS FROM FHWA’S TRAFFIC NOISE MODEL?

摘要

In a study to assess the accuracy of TNM, many hours of highway traffic noise data were collected at numerous sites (at multiple distances and two heights above the ground). Four of these measurement sites give insight to how well TNM is predicting the sound levels when the sound is propagating over acoustically hard ground. When comparing the measured sound levels to those predicted using TNM, it is found that TNM-predicted levels are within 1.5 dB of those measured in the field for one water site (13CA) back to a distance of 900 ft and one pavement site (16MA) to a distance of 200 ft. In these cases, TNM is doing an excellent job in predicting the sound levels. For the other water site (17CT) back to a distance of about 1300 ft and the other pavement site (15CA) back to a distance of 400 ft, the magnitude of the delta between predicted and measured levels ranges from about 0 to 4 dB. As is seen for the site 17CT data, TNM is over-predicting for the very far distances from the roadway. Wind may be a factor in the differences between predicted and measured sound levels for site 15CA. All data will be analyzed in terms of wind speed and direction for the final TNM Validation Phase 1 report. Because of the varying results at all the sites presented here, it is expected that data will be collected at additional sites with acoustically hard ground, and results will be available for Phase 2 of this study.