Research on Measurement Method of Aerodynamic Noise of Reactive Muffler

The aerodynamic noise of the reactive muffler is generated inside the muffler and mixed with the noise of the muffler body, which is difficult to be measured in the exhaust system. Based on two-microphone transfer function method and transmission loss of mufflers in the absence of airflow, this paper proposes a method for measuring the aerodynamic noise of the muffler. On the built-in muffler aerodynamic noise test bench, a special sampling tube was designed to measure the aerodynamic noise of the muffler at different flow velocity. For the sound absorption end with large reflection coefficient, the test and simulation data have large error at low frequency, and a correction formula that can eliminate the reflection of sound waves at the end of the test pipeline and form multiple reflections in the upstream and downstream is derived. The test results of the muffler on the test bench show: The aerodynamic noise data obtained by the sampling pipe is basically consistent with the simulation results by means of leading out measurement, which realizes the measurement of high noise in the pipe by ordinary sensor. The correction formula can effectively eliminate the influence of the reflected wave caused by the end load on the calculation of the transmission loss, reduce the performance requirements of the end sound absorbing material, and ensure the accuracy of the aerodynamic noise measurement.