A single-step measurement method for transmission loss of the muffler based on improved transfer matrix

Transmission loss is a very important acoustic characteristic of the muffler. In order to improve the efficiency of the double-load method for measuring the transmission loss of the muffler, this paper proposes a single-step measurement method for transmission loss of muffler. In addition, the simulation model of the single-step measurement method is established based on the finite element acoustic analysis. For the model, the calculation method of the transmission loss of the muffler is deduced from the theoretical knowledge of the transfer matrix. In the simulation, the sound pressure data of six positions in the model are obtained, and the transfer matrix is used to calculate the transmission loss of the muffler. Then, two simulation comparison experiments were done. In order to verify the validity of the single-step measurement method, the first comparison experiment was to compare the transmission loss of the muffler simulated by the single-step measurement method with their theoretical transmission loss in the finite element acoustic analysis. The results of the simulation validation test cases showed that the transmission loss of the muffler obtained by the single-step measurement method was consistent with the theoretical value. The second comparison experiment was to compare the transmission loss obtained by the single-step measurement method with the transmission loss obtained by the double-load method. The results of the simulation validation test cases showed that at certain frequencies, the transmission loss obtained by the single-step measurement method was more accurate than the transmission loss obtained by the double-load method. In conclusion, the single-step measurement method proposed in this paper can accurately obtain the transmission loss of the muffler with only one measurement, which improves the measurement efficiency.