Active control of the blade passage frequency noise level of an axial fan with aeroacoustic sound sources

Abstract

This paper presents results of a research project on active control of the blade passage frequency tone of an axial fan. The secondary sound field is generated by aeroacoustic sources, which are produced by actively controlling the flow around the impeller blade tips. Both amplitude and phase can be controlled in such a way that a destructive superposition with the primary sound field is possible. The flow distortions can be achieved by using different actuators; results using steady and unsteady jets of compressed air and piezo-electric actuators are presented.