Asymmetric Loss-Induced Perfect Sound Absorption In Duct Silencers

We investigate a duct silencer consisting of coupled resonators for perfect sound absorption. The device is composed of pairs of compact, ring-shaped Helmholtz resonators stacked along a duct. To study the effect of asymmetric intrinsic losses on the absorption performance, the resonators within each pair have the same dimensions (i.e., the identical resonance) but with different intrinsic losses. We find that the perfect absorption is realized by carefully choosing asymmetric intrinsic losses to the coupled resonators within each pair. The device with optimized losses exhibits exceptional point-like characteristics. This study provides not only a solution for practical duct systems but also allows thorough understanding of the role of asymmetric loss in degenerate resonators.