Abstract: The order noise in low-frequency band has great impact on the sound quality of exhaust noise. The muffler with valve becomes one of the means to eliminate low-frequency noise. The actual muffler with valve is analyzed by experiment and three-dimensional numerical simulation methods. It is found that the resonance frequency shift towards high frequency as the valve’s opening degrees increase. Further, a sub structural unit, named adjustable lumped inertance resonator(ALIR), is extracted from the actual muffler with valve. Three-dimensional numerical simulation and an in-line lumped element model are used to calculate the lumped inertance of the valve structure with different opening angles. The lumped model of ALIR is established. The results show that the lumped inertance, which changes with the valve’s opening degrees, is the key factor on the shifting of resonance frequency. Therefore the low frequency silencer mechanism of the muffler with valve is successfully revealed. At last, actual vehicle test is implemented with the muffler with valve and a contrast muffler. It is found that the muffler with valve can effectively eliminate the order noise tracing the engine speed times.

Key words: exhaust order noise, lumped inertance, resonator, valve structure