Influence of a wall impedance insertion on the behavior of the acoustic field in a waveguide

A rigid waveguide with an impedance covering occupying a bounded portion of its surface is considered. The influence exerted by the impedance insertion on the behavior of the waveguide field downstream of the insertion is studied depending on the impedance value, type, and the relative size of the impedance insertion. Special waveguide field propagation modes are found, and the areas of local maxima in the field suppression level are examined in the case of a layer, circular, and rectangular waveguide.