PURPOSE: To perform effective erasure of blade noise through the proper generation of control sounds by providing a control sound source to generate a plurality of control sounds such that directionality is variable in a manner to match with directionality of blade noise of a helicopter.

CONSTITUTION: A control sound source 1 is provided for generating a plurality of control sounds directionality of which is variable according to directionality of blade noise generated by the blade 02 of a helicopter 01. The control sound source 1 forms an assembly of a plurality of control sound sources 1a to generate respective control sounds realizing a control sound having directionality matching with directionality of blade noise. When reduction of the generation of blade noise is controlled, a control signal to erase blade noise is generated by a control device 2, which sets a delay time of each of a plurality of the control sounds generated by the control sound source 1 and generates a control sound having directionality matching with directionality of blase noise. This constitution causes effective reduction of the generation of a blade end vortex interference noise, a problem on which is most apt to arise in terms of an auditory sensation.