Systems and methods for adjusting harmonic cancellation

A method for harmonic cancellation, comprising:

• producing, via a feedback sensor disposed within a cancellation zone within a cabin of a vehicle, a feedback signal corresponding to audio within the cancellation zone;
• producing, via a controller, a harmonic cancellation signal that, when transduced into an acoustic signal, reduces audible harmonics from a harmonic noise source at a harmonic frequency within the cancellation zone, wherein the harmonic cancellation signal is adjusted according to a comparison of the feedback signal at the harmonic frequency to at least one of a saturation threshold or the feedback signal at one or more sideband frequencies offset from the harmonic frequency;
• and
• transducing, via a speaker disposed within the cabin and configured to receive the harmonic cancellation signal, the harmonic cancellation signal into acoustic harmonic cancellation audio to reduce the audible harmonics within the cancellation zone,
• wherein the method further comprises:
• generating, via the controller, a complex conjugate oscillation signal based on an oscillation signal;
• generating, via the controller, a first frequency offset oscillation signal by adding a frequency offset to the complex conjugate oscillation signal;
• generating, via the controller, a second frequency offset oscillation signal by subtracting the frequency offset from the complex conjugate oscillation signal;
• generating, via a downconverter implemented by the controller, a baseband feedback signal, a first offset baseband signal, and a second offset baseband signal by mixing down the feedback signal according to the oscillation signal, the first frequency offset oscillation signal, and the second frequency offset oscillation signal;
• and
• generating, via a saturation low pass filter (LPF) implemented by the controller, a saturated feedback signal, a first offset saturated signal, and a second offset saturated signal by filtering the baseband feedback signal, the first offset baseband signal, and the second offset baseband signal, wherein the cancellation adjustment signal is determined based on the saturated feedback signal, the first offset saturated signal, and the second offset saturated signal.

A system to control operation of a harmonic canceller, comprising:

• a feedback input to receive a feedback signal from a feedback sensor within a cancellation zone of a cabin of a vehicle, wherein the feedback signal corresponds to audio with the cancellation zone;
• a controller configured to produce a harmonic cancellation signal that, when transduced into an acoustic signal, reduces audible harmonics from a harmonic noise source at a harmonic frequency within the cancellation zone, wherein the harmonic cancellation signal is adjusted according to a comparison of the feedback signal at the harmonic frequency to at least one of a saturation threshold or the feedback signal at one or more sideband frequencies offset from the harmonic frequency;
• and
• an output configured to adjust one or more parameters of the harmonic canceller according to the comparison,
• wherein the controller is further configured to:
• generate a complex conjugate oscillation signal based on an oscillation signal;
• generate a first frequency offset oscillation signal by adding the frequency offset to the complex conjugate oscillation signal;
• generate a second frequency offset oscillation signal by subtracting the frequency offset from the complex conjugate oscillation signal;
• generate, via a downconverter, a baseband feedback signal, a first offset baseband signal, and a second offset baseband signal by mixing down the feedback signal according to the oscillation signal, the first frequency offset oscillation signal, and the second frequency offset oscillation signal;
• and
• generate, via a saturation low pass filter (LPF), a saturated feedback signal, a first offset saturated signal, and a second offset saturated signal by filtering the baseband feedback signal, the first offset baseband signal, and the second offset baseband signal, wherein the harmonic cancellation signal is determined based on the saturated feedback signal, the first offset saturated signal, and the second offset saturated signal.