Active noise cancellation in a waveguide in the presence of flow

Active sound cancellation in a waveguide by applying a receiver-emitter placed on the waveguide wall in the presence of a constant-velocity flow in the waveguide is studied. The acoustic field propagating inside the waveguide together with the flow is measured and used to determine the amplitudes and phases of auxiliary emitters whose field is applied to suppress the incident field in the waveguide.