Research On Acoustic Signal Directional Picking Based On Microphone Array

With the development of science and technology,speech signal processing plays an important role in Artificial Intelligence,Modern Communication and Multimedia Technology.Directional sound capture is a kind of speech signal processing,which is mainly used in speech signal enhancement to suppress and shield noise and interference signals.Microphone array is widely used as the front-end acquisition system of directional sound capture system in speech signal enhancement system,because of it's spatial selectivity.The performance of microphone array pickup system is mainly affected by the number of array elements,array geometry and array processing algorithm.In this paper,we will consider the performance of array directional sound capture from these aspects.Microphone array signal processing algorithm plays an important role in the performance of the whole pickup system.When using beamforming algorithm to process the collected acoustic signal,several important performance indicators must be considered,such as array gain,robustness,main lobe width,side lobe response and so on.Because these performances are interrelated,other performances tend to deteriorate when you just optimize one index.In this paper,the convex optimization method based on Minimax criterion is used to optimize the beam pattern.It can make a reasonable compromise among the main lobe width,sidelobe level and robustness compared with Delay-and-Sum(DAS).And the method can control the main lobe width of the beam which does not change with the frequency,reducing the interference component of the speech signal in the low frequency band,improving the quality of pickup,and ensure the robustness of the system.The effectiveness of the proposed method is verified by Matlab simulation and experiment.Because digital MEMS microphone integrates preamplifier circuit and ADC,it has strong anti-interference ability and low power consumption.Also it is widely used in consumer electronics field,and very suitable to be placed on PCB.Therefore,this paper uses Lou's SPM0423HD4H-WB digital MEMS microphone as the unit to collect acoustic signals.The topological structure of the array usually depends on the application of the array,and is limited by the space and cost.In this paper,a 6*6 rectangular grid array with 36 elements and 4 cm element spacing is designed,which is evenly placed on the PCB as the front-end of sound capture system,than the performance of the array is analyzed.The signal is collected and processed by FPGA,and the pulse density modulation signal is demodulated on the FPGA to achieve the goal of directional pickup of far-field acoustic signal.