IMPROVED METHOD FOR SELECTING SCALE FACTORS AND MODEL MATERIALS FOR SCALE MODELLING OF OUTDOOR SOUND PROPAGATION

✍ Scribed by T.A. BUSCH; M.R. HODGSON

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 214 KB
• Volume: 243
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.2000.3462

✦ Synopsis

Critical to the development of an acoustical scale model to be used to measure the e!ectiveness of roadside noise barriers is the selection of both a model scale and materials with which to construct the scale model. Previous work on acoustical scale modelling has typically proceeded by "rst selecting a scale factor, and then selecting appropriate scale-model materials. This paper reports an improved technique for simultaneously specifying both the optimal scale factor and the optimal modelling materials. The technique was used to specify both a scale factor and model materials to simulate asphalt, hard-packed-earth berms and ground, re#ective noise barriers and acoustically hard and soft surface treatments, for use in a subsequent scale-model study of optimal roadside noise-barrier design [1,2]. Model materials*for example, materials to model the ground and noise barriers * are sought that have the best possible scaled acoustical properties when compared to the real surfaces at the test frequencies of interest. The fundamental acoustical property for these materials is the normal-incidence acoustical impedance of the locally reacting boundary. Real ground materials are not of use in modelling their own acoustical properties at scaled frequencies, since they do not have the same properties after scaling. The accurate choice of model materials is crucial to the accuracy of the scale-model tests.