基于声号筒增敏的微热流MEMS矢量水听器研究

New vector hydrophone is one of the hot spots in the research of underwater acoustic transducers and it is widely used in many fields of underwater acoustics. The development of vector hydrophone based on MEMS is an important direction for the development of vector hydrophone to low frequency, miniaturization and low cost. Novel vector hydrophone is one of the hotspots in the research of underwater acoustic transducers, and it is widely used in many fields of underwater acoustics. The development of vector hydrophone based on MEMS is an important direction for the development of vector hydrophone to low frequency, miniaturization and low cost. This project is based on the successful application of dual-wire particle velocity sensor in aeroacoustics to solve the problem of serious sensitivity attenuation when it is applied underwater. A method of combined sensitization of multi-pair hot wire microstructures and acoustic horn is proposed. The physical model of multi-wire sensing element is established by analytic method and multi-physical field finite element simulation method, and the physical parameters affecting the sensitivity and bandwidth of the sensor are analyzed. By reasonably selecting the structural parameters, the sensitivity is increased. The sensitization model of physical structure based on acoustic horn is established. Under the premise of not increasing the electrical noise, the linear physical sensitization in the working frequency band is realized. It is expected that the sensitization can be increased by 20 dB in the frequency range of 20 Hz to 1 KHz. It is applied to underwater by suitable packaging. According to the calibration specification of vector hydrophone, the sensitivity, bandwidth and directivity of vector hydrophone are measured. In order to lay a foundation for its application in underwater acoustic engineering, the flow noise suppression ability of the system is tested in typical turbulent waters.

新型矢量水听器是目前水声换能器研究的热点之一，在水声学多个领域中有广泛的应用需求。MEMS矢量水听器是矢量水听器向低频、小型化、低成本发展的一个重要方向。本项目以双丝质点振速传感器在空气声学中成功应用为基础，解决其水下应用时，灵敏度衰减严重的问题，提出多对热丝微结构及声号筒联合增敏方法，利用解析法与多物理场有限元仿真的方法，建立多丝敏感单元物理模型，分析影响传感器的灵敏度及带宽的物理参数，通过合理选择结构参数，增加其灵敏度；建立基于声号筒的物理结构增敏模型，在不增加电噪声的前提下，实现在工作频段的线性物理增敏，预计可实现在20Hz~1KHz频段增敏20dB；通过合适的封装形式，将其应用到水下，并依据矢量水听器校准规范，对其灵敏度、带宽及指向性等重要参数进行测量，对其在典型湍流水域进行流噪声抑制能力测试，为其在水声工程应用奠定基础。

本研究提出了一种具有更低热噪声的三丝式微热流传感器敏感单元，通过对三维敏感单元的特性仿真，研究了电流，质点振速，声波频率，声波入射方向与该传感器之间的物理关系，优化了传感器敏感单元的几何尺寸，通过体硅微加工技术完成了三丝式敏感单元的设计制作。针对传感器水下灵敏度衰减的问题，提出了微型声号筒增敏结构，通过Comsol 热粘性声学模块仿真，建立声号筒的仿真模型，设计一种双锥管型声号筒，对其开口半径，锥角参数仿真，比较不同结构下的增益因子，确定了声号筒最优尺寸，采用3D 打印工艺研声号筒增敏单元，经验证，三丝结构及声号筒联合增敏效果高于15dB。通过对水下封装外壳的声场仿真分析，确定了聚氨酯外壳的最优尺寸，降低封装外壳对声场的影响。设计了质点振速与声压联合的封装结构，研制三热丝MEMS矢量水听器样机，利用驻波场法对水听器的声压灵敏度，指向性，本底噪声进行测试，与前期研制的双丝式MEMS 矢量水听器相比，经测试，在5Hz~800Hz内灵敏度为-185dB±3dB，具有良好的8字指向性，指向性曲线平滑，横向抑制比大于30dB，在20~800Hz频段，其本底噪声低于1级海况浅海噪声。热丝式矢量水听器可直接测量质点振速，其低频及甚低频段灵敏度及信噪比相对传统同振加速度型矢量水听器具有绝对优势，另外，其体积小，可刚性连接，且可通过MEMS工艺较好的控制其一致性，未来在水下成阵以及小型无人潜器小型阵列低频远距离探测方面具有一定的应用前景及军事意义。