State departments of transportation (DOTs) periodically receive complaints from residents about increases in traffic noise that residents believe are the result of noise reflected from a new noise barrier. With the limited analytical tools currently available, DOTs are unable to conclusively determine if complaints about reflected noise are the result of actual or perceived changes in noise characteristics. The Federal Highway Administration’s (FHWA) Traffic Noise Model
currently does not model single barrier reflections, making it difficult for DOTs to determine when absorptive surface treatments on single noise barriers or other structures (e.g. retaining walls) could be beneficial. Where reflected noise may affect adjacent residents, a number of state DOTs are addressing these concerns by specifying sound-absorbing surface treatments on all noise barriers. However, installation of absorptive barrier surfaces may involve increased project construction costs as well as increased maintenance costs related to the durability of such treatments. Research is needed to enable state DOTs to understand how diverse site conditions may affect reflective noise. Diverse site conditions may include, but are not limited to, topography, roadway functional classification, barrier heights, number of traffic lanes, differing barrier materials, differing pavement surfaces, variable traffic mix scenarios (e.g., high vs. low truck percentages), and weather conditions. Research is also needed to produce insight and data to support validation of future noise analyses and methodologies involving reflected noise from single barriers.
The objectives of this research are to (1) determine the spectral noise level characteristics of the overall noise in the presence of a single absorptive or reflective noise barrier for positions on the opposite side of a roadway through the collection of field measurements from diverse sites, and (2) summarize and analyze the implications of the research results for purposes of understanding the actual and perceived effects of reflected noise.
Phase 1 of this project focused on reflective barrier surfaces.
Phase 2 of this project focused on absorptive barrier surfaces.