基于分流电路和柔性壁面耦合的管道低频噪声控制方法研究

Duct noise is one of the most important parts of environmental noise. In this project, a kind of electro-mechanical-acoustic coupling unit is presented. In the low-frequency region, due to the coupling between cavities and flexible structures in different units, multiple adjacent resonant peaks are found in the transmission loss curve. Meanwhile, the cancellation between the electrical impedance and the mechanical impedance creates a "soft" acoustic segment in low-frequency region. Compared to the traditional passive noise controlling, the current method possesses both the superiority in bandwidth and higher low-frequency performance. The main structures of the current project cover the following contents. First, with the employment of coupling impedance model, the impedance matching rules between the medium and the coupling unit, the strategy of parameter optimization and the character of sound absorbing/reflection will be explored. Then, the validity of the equivalent impedance model and the working frequency range will be checked in the impedance testing of the unit, while the transmission loss of this silencer will be measured in an acoustic tube rig. Finally, a method of broadband noise controlling, especially in the low frequency range, will be developed.

管道噪声是环境噪声中的一个重要组成部分。本项目提出了一种声腔-柔性结构-分流电路耦合单元。在低频范围内，利用多个单元之间声腔-柔性结构的耦合，形成多个邻近的传递损失峰；同时，利用分流电路的电阻抗抵消腔室声阻抗，进而在低频范围内营造一段声学软边界。与传统被动式管道噪声控制方法相比，本方法既能保持被动式控制的带宽优势，又能拓展其低频消声频率的下限。本项目的主要研究内容为：利用建立的耦合阻抗模型，研究声媒质和耦合单元之间的阻抗匹配规律、参数优化方法、声反射/吸收特性。通过阻抗测试实验研究等效阻抗理论模型的准确性、适用频率范围等，通过声管实验检验这种消声器的传递损失，最终形成一种低频管道噪声控制方法。

针对管道低频噪声控制问题，本项目利用多个声腔-柔性结构耦合单元形成多个邻近的传递损失峰，进而在低频区域实现宽频的降噪效果。项目开展过程中分别对柔性膜片耦合单元和扬声器耦合单元的声反射特性进行了研究，建立了其声学分析方法，分析了耦合单元的结构尺寸、物性参数、电路参数等对单元声反射/吸收的效果的影响。对相关参数进行了匹配，在腔室容积固定的情况下形成了耦合单元的最优化设计。最后设计了试验台，通过试验验证了耦合单元的声学计算模型。对于双膜片耦合单元，腔室内气体的声速和密度是影响结构响应的主要因素，应选用低密度气体填充腔室，应减少柔性体自身的附加质量以增强结构的响应；对于双扬声器耦合单元，应选择低结构阻抗的扬声器及其匹配背腔，使更多的声扰动能量在电路中传递；新提出的双扬声器单元使用电路进行耦合连接，空间布置更加灵活，特别适用于对管道低频线谱的被动控制。