A review of natural means for noise abatement
* Presenting author
In addition to wavefront-spreading and air absorption, noise from sources near the ground can be abated during its path to the receiver. ‘Natural’ ways of doing this are described. While the reduction in sound levels attributable to ground effect, sometimes called ground absorption, is included in prediction schemes for surface transport noise, it is possible to increase it either by choosing particular types of acoustically-soft ground surface or by deliberately introducing roughness on an acoustically-hard ground. The most effective acoustically-soft grounds are those with low flow resistivity and recent cultivation without compaction. Low parallel walls or lattice arrangements have been shown to be useful forms of roughness. Reflections from façades and barriers can be reduced by vegetative coverings. While hedges offer relatively little noise reduction, 15 m wide belts of trees can be designed to give on the order of 10 dB reduction at a receiver 30 m from a road. Potential noise reductions from combining ‘natural’ methods in situations where barriers are not feasible will be explored.