Sound Transmission of Mufflers Lined with Micro-perforated Panel Absorbers with Parallel-arranged Cavities of Different Depths

Micro-perforated panel (MPP) mufflers act as a critical role in duct silencing and are introduced as an alternative to conventional porous absorbers adapting to airflow conditions of humidity, cleanliness and high velocity. However, mufflers lined with usual single-layer MPP absorbers are effective only in a narrow band around the MPP absorber resonance frequency. To improve sound transmission loss (STL) in a wider band, a kind of mufflers lined with MPP absorbers with parallel-arranged cavities of different-depths (PCD) is proposed for investigation in the paper. Parameter optimizations, including MPP parameters and PCD optimization, are conducted in simulations with finite element method (FEM). The STL of mufflers lined with the PCD-MPP absorbers is investigated by comparisons with that of mufflers lined with conventional porous materials. Results show that mufflers lined with the PCD-MPP absorbers can be optimized for effective STL in a wide band compared with porous material liners. The PCD-MPP absorbers lined mufflers proposed in this paper have great potentials in practical applications. Keywords: Micro-perforated panel; Mufflers; Sound transmission loss; Finite element method; Sound absorber * Corresponding