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An investigation is presented into the performance of parallel barrier configurations, using acoustical scale modeling. A realistic geometry is investigated, with the source being positioned over a paved roadway and the receiver over grass-covered ground. The grass-covered ground surface was properly modeled in terms of its impedance. Results were obtained for a range of barrier types, and demonstrate that frequency dependent effects are evident in barrier insertion loss data. In most cases, the barrier on the far side of the source did not significantly affect sound levels at the receiver. The most effective barrier design was found to be that of a gradual grass-covered slope up to an upright, thin barrier.

Dynamic Gauging of Soft Fouling Layers on Solid and Porous SurfacesThe experimental determination of characteristic parameters of soft coatings such as biofilms and protein deposits is essential for the study of biotechnological and chemical engineering problems. The technique of fluid dynamic gauging allows the thickness and strength of soft fouling layers to be measured in situ and in real-time under different flow conditions. It is possible to monitor the thickness and strength of biofilms and protein deposits. Different operating modes and nozzle designs allow deposit specific investigations. This paper reports some recent developments of the technique.