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面向数字声音重建的静电MEMS扬声器优化及阵列加权方法

Optimization of Electrostatic MEMS Speakers and Array Weighting Methods for Digital Sound Reconstruction

  • 摘要: 针对数字声音重建(DSR)技术中扬声器瞬态声压输出偏低及二值驱动约束下的波束赋形能力不足问题,本文对静电MEMS扬声器单元结构参数进行优化,并对阵列指向性与加权方法进行分析研究。首先,通过优化振膜厚度、边长及空腔高度,在12 V直流偏置与12 V交流驱动下,在谐振频率76 kHz时使单元于1 mm距离处的声压级提升至72.6 dB,具有较高的瞬态声压输出能力,响应时间小于23 μs,且声学输出满足线性叠加要求,符合DSR技术要求。其次,构建均匀平面方阵,对阵元数量与间距对指向性的影响进行分析,确定最优阵列配置为32×32、阵元间距λ/2,阵列主瓣宽度3.14°。最后,针对DSR阵列二值驱动特性,提出基于误差扩散的单元密度映射加权方法,将连续权值转换为二值开关状态。仿真结果得出,采用泰勒加权时,32 × 32阵列的峰值旁瓣电平为−27.49 dB,较未加权的−13.29 dB显著改善,表明该方法能够一定程度上逼近理想连续加权并抑制旁瓣电平。本文为DSR扬声器阵列的声场控制提供了有效技术方案。

     

    Abstract: To address the issues of low transient sound pressure output and insufficient beamforming capability under binary drive constraints in digital sound reconstruction (DSR) technology, this paper optimizes the structural parameters of electrostatic MEMS speaker units and investigates array directivity and weighting methods. First, by optimizing the diaphragm thickness, side length, and cavity height, under 12 V DC bias and 12 V AC drive, the sound pressure level of the unit at a distance of 1 mm is increased to 72.6 dB at the resonant frequency of 76 kHz, achieving high transient sound pressure output capability, with a response time of less than 23 μs. The acoustic output satisfies the linear superposition requirement, conforming to DSR requirements. Second, a uniform planar array is constructed to analyze the influence of the number of elements and element spacing on directivity. The optimal array configuration is determined as 32 × 32 with an element spacing of λ/2, achieving a main lobe width of 3.14°. Finally, in view of the binary drive characteristic of DSR arrays, a unit density mapping weighting method based on error diffusion is proposed, which converts continuous weights into binary switching states. Simulation results show that with Taylor weighting, the 32 × 32 array achieves a peak sidelobe level of −27.49 dB, which is significantly improved compared with −13.29 dB for the unweighted case, indicating that the method can approximate ideal continuous weighting and effectively suppress sidelobe levels to a certain extent. This work provides an effective technical solution for sound field control in DSR loudspeaker arrays.

     

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