In an increasing number of situations on the U.S. urban and suburban highway system, noise barriers are being considered to protect residences on both sides of a roadway. The scheme of two vertical parallel barrier walls forms the parallel barrier problem. In this case, in addition to the sound waves that reach the receiver by diffraction over the near barrier, sound waves caused by complex pavement-barrier-ground reflection and diffraction mechanisms can reach the receiver, thus degrading the effectiveness of the near barrier. In this paper, the result of the first application of the tilted parallel barrier program to a highway project are presented, along with attempts to verify aspects of the model through comparisons with data that exist in the literature. The model provides excellent agreement in the classical problem of an impedance boundary. It also meets reasonable expectations for parallel vertical, tilted parallel, and parallel absorptive barrier performance when a frequency-dependent optimum design can be selected.
Abstract