A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coeff...A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coefficient of the acoustic structure are calculated via means of equivalent circuit.MATLAB is used to calculate the relationship between the parameters of the ontology structure and the sound-absorption coefficient and the sound insulation.It is revealed that the sound barrier of the new ontology structure is 7.659.80 dB,which is more than the sound barrier of the traditional reflective structures.The relationships among the parameters of sound-absorption structure,sound-absorption coefficient,and sound insulation performance are obtained.In addition,the parameters can be transformed to satisfy the noise reduction requirements of various road sections,which has a admirable adaptability.The acoustic barrier can have tremendous acoustic performance only if there is a splendid sound insulation in the traffic noise frequency band.展开更多
We apply the fast multipole method (FMM) accelerated boundary element method (BEM) for the three-dimensional (3D) Helmholtz equation, and as a result, large-scale acoustic scattering problems involving 400000 elements...We apply the fast multipole method (FMM) accelerated boundary element method (BEM) for the three-dimensional (3D) Helmholtz equation, and as a result, large-scale acoustic scattering problems involving 400000 elements are solved efficiently. This is an extension of the fast multipole BEM for two-dimensional (2D) acoustic problems developed by authors recently. Some new improvements are obtained. In this new technique, the improved Burton-Miller formulation is employed to over-come non-uniqueness difficulties in the conventional BEM for exterior acoustic problems. The computational efficiency is further improved by adopting the FMM and the block diagonal preconditioner used in the generalized minimum residual method (GMRES) iterative solver to solve the system matrix equation. Numerical results clearly demonstrate the complete reliability and efficiency of the proposed algorithm. It is potentially useful for solving large-scale engineering acoustic scattering problems.展开更多
A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microp...A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microperforated tube into N segments, and assuming the flow speed and temperature are constant in each element, sound pressure and volume velocity of each segment can be readily acquired. The transmission matrix of microperforated muffler can be established based on the continuity condition of adjacent elements on the boundary. The numerical results of the present theory are calculated and the experiment is performed in Shanghai-495A engine. The experimental results of microperforated muffler show that they are in good agreement with the theoretical results.展开更多
基金National Natural Science Foundation of China(No.51175195)Guiding Plan of Textile Industry Federation,China(No.2017053)
文摘A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coefficient of the acoustic structure are calculated via means of equivalent circuit.MATLAB is used to calculate the relationship between the parameters of the ontology structure and the sound-absorption coefficient and the sound insulation.It is revealed that the sound barrier of the new ontology structure is 7.659.80 dB,which is more than the sound barrier of the traditional reflective structures.The relationships among the parameters of sound-absorption structure,sound-absorption coefficient,and sound insulation performance are obtained.In addition,the parameters can be transformed to satisfy the noise reduction requirements of various road sections,which has a admirable adaptability.The acoustic barrier can have tremendous acoustic performance only if there is a splendid sound insulation in the traffic noise frequency band.
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. 2010MS080)the Research Fund for Doctoral Program of Higher Education of China (Grant No. 20070487403)
文摘We apply the fast multipole method (FMM) accelerated boundary element method (BEM) for the three-dimensional (3D) Helmholtz equation, and as a result, large-scale acoustic scattering problems involving 400000 elements are solved efficiently. This is an extension of the fast multipole BEM for two-dimensional (2D) acoustic problems developed by authors recently. Some new improvements are obtained. In this new technique, the improved Burton-Miller formulation is employed to over-come non-uniqueness difficulties in the conventional BEM for exterior acoustic problems. The computational efficiency is further improved by adopting the FMM and the block diagonal preconditioner used in the generalized minimum residual method (GMRES) iterative solver to solve the system matrix equation. Numerical results clearly demonstrate the complete reliability and efficiency of the proposed algorithm. It is potentially useful for solving large-scale engineering acoustic scattering problems.
文摘A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microperforated tube into N segments, and assuming the flow speed and temperature are constant in each element, sound pressure and volume velocity of each segment can be readily acquired. The transmission matrix of microperforated muffler can be established based on the continuity condition of adjacent elements on the boundary. The numerical results of the present theory are calculated and the experiment is performed in Shanghai-495A engine. The experimental results of microperforated muffler show that they are in good agreement with the theoretical results.
