作者: |
Crawford, J. A.; Sharma, S.; Ranft, S.; Storey, B.; Le, M.; Rathod, Y.; Sanchez, A.; Overman, J. |
摘要: |
The 84th Texas Legislature passed House Bill (HB) 790 directing the Texas A&M Transportation Institute (TTI) to perform a study on the implementation and effectiveness of sound mitigation measures on the state highway system and certain toll roads and turnpikes. The bill specified the following: (1) an analysis of the process and methodology used by the Texas Department of Transportation or toll project entity for selecting and implementing sound mitigation measures, including factors that affect the process and how outcomes are determined; (2) an analysis of whether any kind of live testing is conducted at any point to determine the actual traffic noise level for neighboring properties; (3) an evaluation of the effectiveness of the process and methodology described by Subdivision (1) of this subsection in reducing the traffic noise level for neighboring properties; and (4) an evaluation of the effectiveness of implemented sound mitigation measures in reducing the traffic noise level for neighboring properties. TTI researchers pursued answers to these requirements through three major approaches. First, researchers conducted a thorough literature review on federal and Texas noise guidelines, comparing them against five peer state departments of transportation in California, Illinois, Florida, New York, and Washington. The literature review also included a state-of-the-practice review of noise mitigation techniques and a review of selected environmental assessment documents from 2010 to present that evaluated the estimated costs of noise walls. Second, researchers conducted interviews with Texas toll authorities that were included in the scope of HB 790. The interviews addressed a wide range of topics, from planning to design of noise mitigation measures. Finally, the researchers performed field sound level measurements within three projects to compare measured sound levels against predicted sound levels. Acoustics is a technical field. At its foundation is understanding how sound is generated by frequency and pressure, transmitted through mediums such as air, and perceived by the human ear. Noise is simply unwanted sound. Sound is measured in decibels (dB). Adjustments are made to sound measurements to account for high and low frequencies to approximate how an average person hears sounds. This adjustment is called A-weighting, expressed as dB(A). The following sections summarize the results of the HB 790 requirements. Detailed discussion is provided in the body and appendices of this report. |