组合声源测试消声器传递损失的噪声信号修正方法

针对某些传递损失较大的消声器,现有白噪声测试设备的单一噪声源发生器无法满足消声量的测试需求。通过采用低频和中频两种声源发生器,利用过渡管道与测试管道垂直连接的方式,实现了两种声源组合发声对消声器声学性能的测试。为了解决过渡管道与组合声源系统连接处声阻抗变化,导致输出的噪声信号频谱特性随机波动的问题,提出了一种噪声信号的修正方法。该方法基于四传感器法测量过渡管道声阻抗,根据过渡管道传递矩阵,以随机白噪声为激励源输出的管口噪声作为输出声压信号,得到组合声源系统的输入声压信号,实现了对组合声源系统声音信号的补偿。实验结果表明,与传统均衡器调节方法相比,该方法能够在较宽的测试频率范围内输出平稳的声压信号;其次,利用修正前后的声学信号对扩张腔的传递损失进行测量,修正后得到的测试曲线与理论值吻合度较高,证明了该方法的可行性。

A noise signal correction method for muffler transmission loss measurement with combined sound source

For some mufflers with high transmission loss, the single noise source generator of existing white noise test equipment cannot meet the test requirements of the noise reduction amount. In this paper, the acoustic performance of muffler is tested by the combination of low frequency and medium frequency noise generators and the vertical connection between the transition pipe and the test pipe. In order to solve the problem of random fluctuation of the spectral characteristics of output noise signal, which is caused by the change of acoustic impedance at the junction of the transition pipeline and the combined sound source system, a correction method for combining noise signals is proposed. This method is based on the four-sensor method to measure the acoustic impedance of the transition pipeline. According to the transfer matrix of transition pipeline, the noise at the pipe orifice, which is the output of a random white noise excitation source, is used as the output sound pressure signal to obtain the input sound pressure signal of the combined sound source system and realize the sound signal compensation of the system. The experimental results show that compared with the traditional equalizer adjustment method, this method can achieve a stable sound pressure signal output in a wide range of test frequencies and the noise signal obtained meets the test requirements. Secondly, the acoustic signal before and after the correction is used to measure the transmission loss of the expansion cavity. The measured curve after correction is in good agreement with the theoretical one, which proves the feasibility of this method.