Waveguide insulator – theory and experiment

The theory of sound propagation in waveguides with a system of resonators on the wall is given in [1-2]. The papers present theoretical data showing that the use of a chain of identical Helmholtz resonators on the walls of a waveguide reduces the sound pressure levels effectively not only at the resonant frequency, but also at frequencies which are significantly higher than the resonant frequency. This theory was called by the authors of [1, 2] the theory of waveguide isolation (WI). Nowadays, the decades later, the idea of using a set of identical resonators has been widely developed in creation and research of acoustic metamaterials – artificial structures with unusual wave properties (see for example [3-6]). At the same time, the works [1-2] remained almost unnoticed. This paper is devoted to experimental and numerical verification of the WI theory. The design of the studied WI, a simple experimental setup, the results of the experiment and numerical experiment are described