Efficiency of Actively Controlled Surface Impedance of Upper Sections Attached to Noise Barriers

Abstract

Based on a mathematical model consisting of a rigid cylindrical body attached to a rigid half plane, the sound pressure on the surface of the cylindrical upper section is actively minimized to divert the tangential power transport along the surface as much as possible. The numerical study considers the possibility of deflecting the incident sound by means of a secondary sound field. The acoustical shadow region becomes more pronounced in both the near and far field, compared with the passive case. For a relatively wide frequency range it is also possible to find optimal arrangements for the secondary sources and for the error microphones. The physical principle studied theoretically can also be realized practically by means of active control. The optimal configurations found in the numerical analysis are proven to be effective in the experiment.