Field Evaluation of Reflected Noise for Sensitive Receptors Across from a Non-Absorptive Noise Barrier Surface
Community & Cultural Concerns, Environmental Process
Research Idea Scope
Residents on the opposite side of a highway from a reflective noise barrier often complain that construction of the barrier has increased noise levels in their area. The cause and nature of the perceived increase in noise levels is not fully understood.
Comprehensive studies of noise-level magnitude, annoyance, and, in particular, 1/3 octave-band frequency analysis of the noise-source spectrum opposite a reflective noise barrier is recommended. These quantitative analyses will then be used to determine if the magnitude and/or composition of the noise level actually changes, or whether the complaints are triggered by the psychological phenomenon of “barrier envy” (nearby residents are not receiving a noise barrier when their neighbors do).
Several state departments of transportation (DOTS) should be canvassed where residents have complained about an increase in noise due to the presence of a recently constructed noise barrier across the highway. Using information about specific sites provided by the DOTs, study sites should be selected that provide equivalent cross sectional topography and traffic operations for both target (across the highway from the reflective barrier) and reference (no barrier) locations. Data for comparative analyses should be simultaneously collected at various setback distances up to 1,000 feet from the roadway. Data should be collected for target locations near the center of the barrier and near the end of the barrier. Simultaneous data should be collected for reference locations under the same traffic conditions. A detailed record of meteorological conditions; for example, wind speed and atmospheric stability, should be maintained during data collection. Using annoyance metrics to identify image events, and especially 1/3 octave-band frequency analysis and meteorological data, traffic noise source and reflected spectra should be analyzed. Results should be assessed against current prediction methodologies. The analysis should identify whether or not a measured shift in the overall noise level and/or frequency content occurs for a given set of traffic operations. Evaluations should consider if the presence of a phenomenon varies with distance or is influenced by geometric or physical parameters such as barrier height and surface roughness, and by vehicle type and under variable traffic mix scenarios (i.e., high versus low truck percentages, low- versus high-speed traffic, etc.).
RNS. Sponsoring Committee: ADC40, Transportation-Related Noise and Vibration