Acoustically soft ground as a highway traffic noise reduction strategy

Acoustically soft ground adjacent to transportation systems can help reduce noise in nearby communities. The effectiveness of soft ground surfaces to reduce highway traffic noise is dependent on the soft ground placement, ground type/material, number/placement of traffic lanes, and vehicle mix. Each specific site geometry and each vehicle noise sub-source location combines to define the region of influence in adjacent communities. The effect of a soft ground strip in the right-of-way (ROW) of a highway is examined on both a broadband and 1/3-octave band basis and as a function of distance using the U.S. Federal Highway Administration Traffic Noise Model (TNM). Examinations as a single noise reduction strategy and combined with quieter pavement are presented for a variety of highway/ROW configurations. Results show a noise reduction of several decibels due to a gravel strip and more combined with quieter pavement.