Barrier-Free Duct Muffler For Low-Frequency Sound Absorption

Abstract

We demonstrate a duct muffler design operating at frequency range that lower than 2000Hz. The device is composed of coupled annular Helmholtz Resonators (HRs) and installed as side branch of a circular ventilation tube to avoid affecting the ventilation. Porous material is employed for the purpose of generating asymmetric intrinsic loss status of the HR. Analytical model based on temporal coupled-mode theory is introduced and numerical simulation technique for structure design are introduced and verified. Experimental study verifies the effectiveness of the design methodology and illustrate that the device can achieve near perfect sound absorption in the desired frequency range. A symmetry configuration of HRs also experimentally proved to be able to conduct sound absorption for sound incident from both sides of the duct. This work provides a solid foundation for the application of the designed muffler and an analytical explanation of the corresponding sound absorption mechanisms.