Studies on an automobile muffler with the acoustic characteristic of low-pass filter and Helmholtz resonator

Tail pipe is a most common structure in mufflers to silence low frequency noise from an engine for its acoustic performance of low-pass filter. Based on the typical structure, a muffler with an interconnecting hole on the tail pipe was proposed to improve its acoustic performance in the present research. Acoustic performances of the proposed muffler were studied experimentally and theoretically in frequency and time domain. It was found that the interconnecting hole enabled the proposed muffler to have a noise attenuation performance of Helmholtz resonator. So the proposed muffler can attenuate the noise of low frequency and middle frequency at the same time. The frequency equation of this structure was derived using the acoustic-electronic analogy. It is useful for estimating the attenuation performance at the stages of predesign or tuning. The influence of structure parameters of the proposed muffler on its acoustic performance was studied. According to the results, the design guideline of this muffler was concluded in the present research.