Systems and methods for virtual microphones in active noise cancellation

A noise cancellation system for a vehicle comprising:

• a reference sensor configured to acquire a reference signal correlated to noise within a vehicle cabin;
• a time domain adaptive weight filter in electronic communication with the reference sensor, configured to apply an adaptive filtering process to the reference signal to produce a noise cancellation signal to cancel noise around ears of one or more vehicle occupants;
• a plurality of speakers positioned within the vehicle cabin and in electronic communication with the time domain adaptive weight filter, configured to emit the noise cancellation signal into the vehicle cabin;
• a plurality of physical error microphones positioned within the vehicle cabin and configured to acquire a residual signal resulting from interaction of the noise cancellation signal and the noise within the vehicle cabin;
• and
• a signal processing unit in electronic communication with the reference sensor, the plurality of speakers, and the plurality of physical error microphones, wherein the signal processing unit comprises:
• a non-transitory memory storing a set of frequency domain subband filters, and instructions;
• and
• a processor, wherein, when executing the instructions, the processor is configured to:
• estimate a frequency domain filtered virtual microphone signal from the noise cancellation signal and a residual physical error microphone signal, and a frequency domain filtered reference signal from the reference signal;
• decompose the frequency domain filtered virtual microphone signal and the frequency domain filtered reference signal into a plurality of frequency domain subband signals;
• calculate a frequency domain subband adaptive filter for each subband of the plurality of frequency domain subband signals to produce a plurality of frequency domain subband adaptive filters;
• and
• update the time domain adaptive weight filter based on a weighted transformation of the plurality of frequency domain subband adaptive filters.

A method for noise cancellation in a vehicle comprising:

• acquiring a reference signal using a reference sensor, wherein the reference signal is correlated with noise in a vehicle cabin;
• processing the reference signal with a time domain adaptive weight filter to produce a noise cancellation signal;
• emitting the noise cancellation signal to cancel noise around ears of one or more vehicle occupants using a plurality of speakers positioned in the vehicle cabin;
• acquiring a residual signal from a plurality of physical error microphones positioned in the vehicle cabin;
• transforming the noise cancellation signal, the residual signal, and the reference signal into a frequency domain noise cancellation signal, a frequency domain residual signal, and a frequency domain reference signal, respectively, using a Fast Fourier Transform (FFT);
• applying a plurality of secondary path filters to the frequency domain noise cancellation signal and the frequency domain residual signal to produce a frequency domain filtered estimated virtual microphone signal, and to the frequency domain reference signal to produce a frequency domain filtered reference signal;
• applying a set of frequency domain subband filters to decompose the frequency domain filtered reference signal and the frequency domain filtered estimated virtual microphone signal respectively into a plurality of frequency domain subband filtered reference signals and a plurality of frequency domain filtered estimated virtual microphone signals;
• determining a frequency domain subband gradient for each subband based on a frequency domain subband reference signal and a frequency domain subband error signal;
• determining a frequency domain normalized step size for each subband based on a power contribution of the frequency domain subband reference signal and the frequency domain subband error signal;
• updating a set of frequency domain subband adaptive filter weights based on the frequency domain subband gradient and the frequency domain normalized step size to produce an updated set of frequency domain subband adaptive filter weights;
• transforming the updated set of frequency domain subband adaptive filter weights from a frequency domain to a time domain using Inverse Fast Fourier Transform to produce an updated time domain adaptive weight filter;
• and
• emitting the noise cancellation signal based on the updated time domain adaptive weight filter to reduce noise around the ears of the one or more vehicle occupants.