Patent ID: 8532828

Claim:
A system for damping audible noise from a drive train, the system comprising: a sensor to detect an audible noise signal from the drive train, the audible noise signal including a vibration component at a frequency corresponding to an acoustic resonant frequency of a mechanical structure surrounding the drive train or a mechanical resonant frequency of the drive train and a noise level proportional to an amplitude of the audible noise signal; a damping circuit configured to produce a damping torque signal, wherein said damping torque signal is a phase shifted and amplified version of the audible noise signal from said drive train, the audible noise signal and damping torque signal having a same frequency; an electrical generator or an electrical motor coupled to said drive train; and a converter to apply the damping torque signal to an air-gap torque of said electrical generator or said electrical motor to reduce said audible noise only when the noise level is greater than a pre-determined threshold noise level.