梯度型非均匀媒质的声传播理论及其阻抗匹配应用

Sound propagation in inhomogeneous media has being one of the main subjects of basic studies in acoustics, relevant to problems like sound propagation in oceanic, sedimentary, and atmospheric environments. The proposed project, arising from the practice of design of the matching layers for high-end ultrasonic transducers, studies sound propagation in continuous media with gradiently varying impedance (or other acoustic properties). It is well-known that impedance matching is fundamental to improve the performance including bandwidth and efficiency of a transducer, but the matching layers designed based on the classic one-quarter wavelength theory are difficult to fulfill both requirements simultaneously. To ultimately overcome the bottleneck restraining the improvement of performance of the high-end ultrasonic transducers, we propose the conception of matching layers of gradiently varying impedance. The project first attempts to establish the theory of sound propagation in this special type of inhomogeneous media and through the multiple layers discretized from the corresponding continuous media, analyze the properties of sound reflection and transmission, and design an optimized scheme for practical design. Finally a novel kind of acoustic functional material will be prepared based on this study and will be used to design matching layers of transducers of high efficacy and wide bandwidth.

非均匀媒质中的声传播问题长期以来是声学的基础研究内容，涉及诸如海洋、海洋沉积、大气等环境下的声传播问题。本项目研究声阻抗（或其它声学性质）呈梯度型连续变化的非均匀媒质（简称梯度型媒质）中的声传播问题。问题直接来源于高性能超声换能器阻抗匹配层的设计与制备实践。众所周知，阻抗匹配是影响超声换能器性能（带宽与效率）的关键技术之一。传统的基于四分之一波长共振透射的匹配技术所制备的匹配层已经不足以满足当前业界对高性能的要求。本项目提出，使用声阻抗率（或其它声学性质）按梯度型连续变化的匹配层有可能解决制约换能器性能的瓶颈。本项目（1）试图建立梯度媒质的声学理论，为新型阻抗匹配层设计技术提供理论基础；（2）根据梯度媒质的声传播理论，研究梯度离散化的多层状媒质中的声传播理论，分析其中的透声性能和最优匹配设计；（3）根据理论方案，制备新型高效宽带的声阻抗匹配材料。

非均匀媒质中的声传播问题长期以来是声学的基础研究内容，涉及诸如海洋、海洋沉积、大气等环境下的声传播问题。本项目研究声阻抗（或其它声学性质）呈梯度型连续变化的非均匀媒质（简称梯度型媒质）中的声传播问题。问题直接来源于高性能超声换能器阻抗匹配层的设计与制备实践。众所周知，阻抗匹配是影响超声换能器性能（带宽与效率）的关键技术之一。传统的基于四分之一波长共振透射的匹配技术所制备的匹配层已经不足以满足当前业界对高性能的要求。本项目提出，使用声阻抗率（或其它声学性质）按梯度型连续变化的匹配层有可能解决制约换能器性能的瓶颈。本项目（1）试图建立梯度媒质的声学理论，为新型阻抗匹配层设计技术提供理论基础；（2）根据梯度媒质的声传播理论，研究梯度离散化的多层状媒质中的声传播理论，分析其中的透声性能和最优匹配设计；（3）根据理论方案，制备新型高效宽带的声阻抗匹配材料。