Analysis of the shielding effect of the noise reduction components in multi-chamber mufflers and optimization of structural parameters

To address the challenges of high-intensity and broadband noise in diesel engine exhaust systems, multi-chamber reactive mufflers have been widely employed. However, complex acoustic coupling effects among internal components often render traditional linear superposition-based design methods ineffective. This study systematically investigates the acoustic characteristics of a complex three-chamber muffler by integrating the acoustic transfer matrix method, finite element numerical simulation, and orthogonal experimental design. An acoustic shielding effect was proposed based on the principle of acoustic impedance mismatch, thereby quantitatively elucidating the physical mechanism through which the upstream silencing unit attenuates the sound attenuation capability of the downstream unit by modifying the boundary conditions. Building upon this understanding, a “frequency band segmentation control” structural decoupling strategy is proposed, which employs non-uniform chamber lengths to suppress modal overlap and incorporates a low-perforation-rate inlet to enhance low-frequency reflection performance. Experimental results demonstrate that the optimized muffler achieves an average noise attenuation improvement of 6.16 dB(A) across the entire frequency range, while reducing exhaust backpressure by 8.98%. This research provides a reference for addressing coupling issues in complex acoustic systems.