Method and apparatus for controlling tonal noise from subsonic axial fans

摘要

An apparatus for reducing a selected tonal noise generated by an axial flow fan (12) operating in a non-uniform flow by locating at least one obstruction (2) in the non-uniform flow such that the at least one obstruction (2) generates a noise that is out of phase with the selected tonal noise. The noise generated by the at least one obstruction (2) interferes with the selected tonal noise, thus reducing the selected tonal noise. It is also contemplated to use additional obstructions to reduce other tonal noises generated by the axial flow fan (12).