Helicopter active noise control system

An active noise control system for a helicopter for effectively nullifying high frequency vibrations emanating from the main transmission gearbox thereof to significantly reduce interior noise levels of the helicopter, comprising:

• modified transmission beam means including mounting hardpoints for interfacing the main transmission gearbox in combination with the airframe of the helicopter, said modified transmission beam means being mechanically stiffened with respect to at least one of the high frequency vibrations emanating from the main transmission gearbox wherein said modified transmission beam means function as a rigid body with respect to said at least one high frequency vibration;
• actuator means mounted in combination with said modified transmission beam means adjacent said transmission gearbox and airframe interface for generating a plurality of single dimensional counterforces having a frequency, magnitude, and phase to effectively nullify said at least one high frequency vibration at said transmission gearbox and airframe interface;
• and
• means operative with respect to said at least one high frequency vibration to detect magnitudes and frequencies of single dimensional components thereof at said transmission gearbox and airframe interface and to provide command signals to control operation of said actuator means to generate said single dimensional counterforces having said frequency, magnitude, and phase to effectively nullify said at least one high frequency vibration at said transmission gearbox and airframe interface wherein the interior noise levels of the helicopter are significantly reduced.