Conventional element based methods for modeling acoustic problems are limited to low-frequency applications due to the huge computational efforts.For high-frequency applications,probabilistic techniques,such as statis...Conventional element based methods for modeling acoustic problems are limited to low-frequency applications due to the huge computational efforts.For high-frequency applications,probabilistic techniques,such as statistical energy analysis(SEA),are used.For mid-frequency range,currently no adequate and mature simulation methods exist.Recently,wave based method has been developed which is based on the indirect TREFFTZ approach and has shown to be able to tackle problems in the mid-frequency range.In contrast with the element based methods,no discretization is required.A sufficient,but not necessary,condition for convergence of this method is that the acoustic problem domain is convex.Non-convex domains have to be partitioned into a number of(convex)subdomains.At the interfaces between subdomains,specific coupling conditions have to be imposed.The considered two-dimensional coupled vibro-acoustic problem illustrates the beneficial convergence rate of the proposed wave based prediction technique with high accuracy.The results show the new technique can be applied up to much higher frequencies.展开更多
To get desired sound absorption,we proposed a novel periodic composite structure comprised of micro-perforated plates(MPPs),porous materials and air cavities.The composite structure is then solved using an equivalent ...To get desired sound absorption,we proposed a novel periodic composite structure comprised of micro-perforated plates(MPPs),porous materials and air cavities.The composite structure is then solved using an equivalent circuit model,with equivalent fluid porous model and Maa’s theory.Distributed four-pole elements are used to handle structures which are not compact compared to the sound wavelength.The model procedures are validated and confirmed as satisfactory by published results and finite-element results.Analysis conducted on a single layer shows that,compared with traditional MPP,the porous addition can increase sound absorption in the low-to-medium frequency range;however,the advantage of porous materials in the high-frequency range is lost.Meanwhile,by arranging the porous materials in parallel and controlling their filling ratios,the absorption curve of the composite structure can be tuned.As to periodic composite structures,it is found that the influence of layer number N is mainly in the low-to-medium frequency range.When N varies,the half-absorption bandwidth increases over 40%(≥380 Hz) compared with a single layer.Compared with multi-layered MPPs,N=2 and N=4 produce an increase of bandwidth by 50%(≥400 Hz) and 30%(≥300 Hz) respectively.As N increases,the sound absorption is better but the enhancement weakens as it tends to the limit of the composite structure.These results show the potential enhancements that can be made to the traditional MPP,which can benefit the research on wideband noise reduction in the low-to-medium frequency range.展开更多
基金This project is supported by National Natural Science Foundation of China(No.10472035).
文摘Conventional element based methods for modeling acoustic problems are limited to low-frequency applications due to the huge computational efforts.For high-frequency applications,probabilistic techniques,such as statistical energy analysis(SEA),are used.For mid-frequency range,currently no adequate and mature simulation methods exist.Recently,wave based method has been developed which is based on the indirect TREFFTZ approach and has shown to be able to tackle problems in the mid-frequency range.In contrast with the element based methods,no discretization is required.A sufficient,but not necessary,condition for convergence of this method is that the acoustic problem domain is convex.Non-convex domains have to be partitioned into a number of(convex)subdomains.At the interfaces between subdomains,specific coupling conditions have to be imposed.The considered two-dimensional coupled vibro-acoustic problem illustrates the beneficial convergence rate of the proposed wave based prediction technique with high accuracy.The results show the new technique can be applied up to much higher frequencies.
基金supported by the National Natural Science Foundation of China (11572137)。
文摘To get desired sound absorption,we proposed a novel periodic composite structure comprised of micro-perforated plates(MPPs),porous materials and air cavities.The composite structure is then solved using an equivalent circuit model,with equivalent fluid porous model and Maa’s theory.Distributed four-pole elements are used to handle structures which are not compact compared to the sound wavelength.The model procedures are validated and confirmed as satisfactory by published results and finite-element results.Analysis conducted on a single layer shows that,compared with traditional MPP,the porous addition can increase sound absorption in the low-to-medium frequency range;however,the advantage of porous materials in the high-frequency range is lost.Meanwhile,by arranging the porous materials in parallel and controlling their filling ratios,the absorption curve of the composite structure can be tuned.As to periodic composite structures,it is found that the influence of layer number N is mainly in the low-to-medium frequency range.When N varies,the half-absorption bandwidth increases over 40%(≥380 Hz) compared with a single layer.Compared with multi-layered MPPs,N=2 and N=4 produce an increase of bandwidth by 50%(≥400 Hz) and 30%(≥300 Hz) respectively.As N increases,the sound absorption is better but the enhancement weakens as it tends to the limit of the composite structure.These results show the potential enhancements that can be made to the traditional MPP,which can benefit the research on wideband noise reduction in the low-to-medium frequency range.
