抗性消声结构声腔模态对其消声特性的影响研究

Effects of Acoustic Modes in Chamber on Acoustic Attenuation Characteristics of Reactive Silencing Elements

为分析抗性消声结构声腔模态对消声器消声性能的影响,以典型3种抗性消声结构为对象,基于有限元法计算了其传声损失及扩张腔室的声模态,分析了扩张腔室声模态和进出口管位置对传声损失的影响规律。研究结果表明:扩张腔室的声模态和进出口管布置对抗性消声结构传声损失的影响非常显著。只有在极低的低频范围内,抗性消声结构的传声损失与基于一维平面波理论模型的传声损失结果才相吻合,进出口管布置位置对传声损失的影响才较小。消声器的进出口管布置位置对腔室的高阶声模态抑制和激发有重要影响,将进出口管布置在扩张腔室声模态节点区域能显著改善消声器中高频消声性能。对某汽车消声器进行改进设计,改进后平均传声损失提高了15.8dB。

In order to study the influence of acoustic modes of reactive silencing structure on muffler acoustic attenuation performance, the transmission losses and acoustic modes in the expansion chamber were calculated by using finite element method with three kinds of typical silencing elements. Futhermore the effect of acoustic modes in the expansion chamber and the locations of inlet and outlet on the transmission losses were analyzed. Only in the extremely low frequency range, the transmission losses calculated by finite element method are in good agreement with that given by one dimensional plane wave theory allowing to have less influence of locations of inlet and outlet on the transmission lesses. While in the middle and high frequency range, noise attenuation performance of the reactive mufflers can be improved significantly when the inlet/outlet is located in the nodal point area of higher order acoustic modes where these modes cannot be excited/responded observably. Finally, the improved design of a car muffler is carried out based on the above results, and the average transmission loss is increased by 15.8 dB.