摘 要:传统的消声器传声损失测量通常是在单末端边界条件下,将消声器上、下游侧作为2个独立声学系统,分别测量上游侧入射功率和下游侧透射功率,进而计算确定其传声损失,该方法未能完全考虑消声器下游侧末端反射波对上游侧的耦合效应,限制了传声损失的测量精度。因此,为了完整计及下游侧末端反射波对上游侧的耦合,提出了基于传递函数的4传声器位置、双末端边界条件传声损失测量方法。并给出了提高传递函数测量精度的传递函数修正算法。在此基础上,以B&K的声学材料测试系统为硬件平台,对典型扩张式消声器进行了传声损失测量分析,实验结果与理论分析结果具有良好的一致性。
Abstract: The traditional measurement of the
transmission loss of muffler was done in single terminal boundary conditions, the sound fields at the upstream side and downstream side of the muffler were considered to be two independent acoustic systems. Then the transmission loss of muffle was determined by calculating the incidence power of upstream side and the transmitted power of downstream side respectively. But it failed to take into account the full coupling effect on the sound field of upstream side for the reflected wave from the terminal of the downstream side of the muffler, limiting the measurement accuracy of the sound transmission loss.
Consequently, in order to take into account the coupling fully, the new measurement method of
transmission loss, which based on transfer function, 4 microphone locations, and dual terminal boundary conditions, was put forward. Furthermore, transfer function correction algorithm which can improve the accuracy of transfer function measurements also
was derived. In the end, the experiment for transmission loss of a typical expansion muffler using hardware platform of B&K acoustical material testing system was done, and the results were consistent with the theory.