封闭空间声场重构的多层等效源法

对于封闭空间内的多途反射声,传统的等效声源法将其等效为距离边界一定距离的单层等效声源体进行声场重构,然而等效源与边界的距离选取依据不确定。因此,为获得等效声源配置的最优距离,在等效声源法(ESM)的基础上构建多层等效声源,提出一种适用于封闭环境声场重构的多层等效声源法(MESM),并依据等效声源的空间分布的稀疏性来获得等效声源强度信息。首先给出多层等效源法的理论依据,其次通过数值计算以及实验测试两种方式对比验证了所提方法。数值结果表明:MESM相比于ESM可在600 Hz以上频段获得低5~10 dB左右的重构误差,但是200 Hz以下的低频重构误差会增加5 dB左右。实验结果表明:MESM可比ESM获得更低的重构误差。文章最后基于数值计算研究了所提方法的主要影响因素。研究表明:虽然MESM会比ESM耗费2倍的计算时间,但在整体频率范围内,MESM可在ESM基础上提升600 Hz以上的重构性能。另外,等效声源的层数和层内数目的改变不会影响声场重构性能,而当传声器数目较多、阵列位置随机、空间边界的吸声系数不是很大时,MESM可获得比ESM更低重构误差,特别是600 Hz以上的中频段区间。 

3D sound field reconstruction for the enclosed cavity using the multilayer equivalent sources method

Conventional equivalent source method always models the reflective waves from boundaries using one layer equivalent sources,but how selecting the optimized distance of equivalent sources is diffcult.The proposed MESM (Multiple layer Equivalent Source Method) mainly uses multiple layer equivalent sources to approximate the desired sound field under the assumption that the equivalent sources are sparsely distributed in the external boundary of the space.Firstly,the details of the proposed method are derived.Secondly,the proposed MESM is validated using numerical simulations in a rectangular cavity and measured data in a cabin.The numerical simulation shows that a lower error of 5-10 dB can be achieved with MESM than ESM for the frequencies higher than 600 Hz and a higher error of 5 dB for frequencies lower than 200 Hz.A higher performance can also be achieved by the experimental data.Next,MESM are investigated through the numerical simulations against different conditions.It turns out that the elapsed time by MESM will be about two times of that by ESM.However,a high reconstructive accuracy for the frequency higher than 600 Hz can be obtained if the sound field in enclosed space is computed using more sensors,a random distribution of microphones and a lower absorption coeffieint.In addition,the performance of sound field reconstruction will not be almost unaffected by the layer number and the number of equivalent source in each layer.