Effectiveness of Six Noise Barriers on I-495: Final Report

About the report:

While measurements made by the Virginia Highway and Transportation Research Council, other departments of transportation, and the Federal Highway Administration have generally shown that acoustical barriers perform as predicted, public acceptance has often been less than unanimous. Some complaints that barriers do not seem to reduce noise levels have been especially surprising. Thus, following a series of interviews of people residing adjacent to several barriers, an acoustical study of barriers was undertaken both to determine the effectiveness of the barriers and to find whether there was any correlation between the noise reductions perceived by the residents and those determined by analysis or measurement. At five of these barriers, pairs of measurements were made, one near a residence where a favorable comment had been made and one where an unfavorable comment had been made. At a sixth barrier, measurements were made only near a residence where an unfavorable comment had been made because of a paucity of good measurement sites near the residences where favorable comments had been made. This very small study, although not statistically meaningful, revealed some interesting trends. For example, many individuals may react to non-acoustical factors, such as problems of maintenance of the areas behind barriers and in other cases, individuals appear to react to their own perceptions of the physical parameters of the barrier rather than to its acoustical effectiveness. One particularly interesting conclusion was that the perception of the barriers' effectiveness tended to be negative when the ear level of a person standing at the door of his house was much closer to the same elevation as the top of the barrier than was the ear level of the person who responded positively.

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