Acoustic attenuation performance through a constricted duct improved by an annular resonator

Abstract

Acoustic attenuation performance through a constricted duct is greatly improved by an annular resonator. A method based on the Green's function for a semi-infinite circular duct is proposed to calculate the transmission loss, where the velocity distributions are assumed to be uniform at the constriction inlet/outlets and at the inlet to the annular resonator. From an analogous acoustical circuit, the effect of higher order evanescent modes on the quarter-wave resonance is described by an extra length. The improved acoustic attenuation performance is also confirmed by an experiment.

Retrieving Effective Acoustic Impedance and Refractive Index for Size Mismatch Samples

“…In Eqs. ( 12)-( 19), G 1 (r, 0; r 0 , 0) and G 2 (r, t; r 0 , t) are Green's function at the interfaces and can be simplified as 31,32 :…”

Acoustic wave manipulation with artificial metasurfaces

“…where 𝐺 1 (𝑟, 0; 𝑟 0 , 0) and 𝐺 2 (𝑟, 𝑡; 𝑟 0 , 𝑡) are Green's function at the interfaces and can be simplified as (Feng et al, 2013;Li et al, 2014b):…”