![]() ![]() The authors analyzed many measurements on different noise barriers, performed on outdoor test sites during an inter-laboratory test organized in the frame of the European project QUIESST5,6,7, having among its objectives the improvement of the CEN/TS 1793-5 measurement method. The European standard explains the measurement procedure in details, but a criterion for validating the measurements and prevent the acquisition of possible invalid data is missing. ![]() This kind of problems is not always easy to recognize when on site. Some errors may anyway occur: for sound reflection, when the signal subtraction procedure1 leaves a small residual for airborne sound insulation, when the barrier under test is highly insulating and so the transmitted signal is very low. The procedure, based on impulse response measurements close to the noise barrier and in the free field, is robust and easily applicable it allows to get the results in real-time just after the measurements, in situ or in laboratory, applying a well defined post-processing to the raw data. The sound reflection and the airborne sound insulation of noise barriers can be measured in-situ according to CEN/TS 1793-51,2,3,4. A question we frequently hear from engineers is "How is the effectiveness of the barrier in the enclosed space?" We believe that predicting the acoustic performance of barrier in a long industrial space would help the engineer to properly locate and select the height of the barrier in the enclosed space. Recently, barrier becomes one of the acoustic measures in the interior design, such as to reduce the equipment noise at the office or machine noise in the industrial area. Introduction The barrier is initially designed in the outdoor area, which is always located beside the highway to eliminate the traffic noise from the residential area. Comparison results with Bradley's prediction so as to verify that these numerical models can quite accurately predict the acoustic performance of the barrier in a long industrial space. Finally, applying the Pierce's formulation to predict the sound field diffracted by the barrier in the ray model. These predictions are compared with the classical ray-based method where the total sound fields are obtained by summing contributions from all image sources either coherently or incoherently. The Parabolic Equation (PE) method and an approximate scheme based on the Helmholtz-Kirchoff formulation are presented. This paper describes the development of two computational schemes for predicting sound propagation behind a barrier in a long industrial space. ![]()
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