Systems and methods for subband virtual path calculation in active noise cancellation

A noise cancellation system for a vehicle, comprising:

• a physical microphone configured to acquire a physical microphone signal correlated to a filtered noise signal within a vehicle cabin;
• a plurality of virtual microphones positioned within the vehicle cabin and configured to acquire a residual signal;
• an adaptive weight filter in electronic communication with the physical microphone signal, configured to apply an adaptive filtering process to the physical microphone signal to estimate a virtual secondary path from the physical microphone to the plurality of virtual microphones;
• and
• a signal processing unit in electronic communication with the physical microphone and the plurality of virtual microphones, wherein the signal processing unit comprises:
• a non-transitory memory storing a set of analysis filters, and instructions;
• and
• a processor, wherein, when executing the instructions, the processor is configured to:
• apply the set of subband analysis filters to decompose the residual signal into a plurality of subband error signals and to decompose the physical microphone signal into a plurality of subband physical microphone signals;
• determine a subband gradient for each subband based on a subband physical microphone signal and a subband error signal;
• calculate a normalized step size for each subband, based on a constant value that is adjusted based on a threshold normalized step size, the threshold normalized step size a non-zero, positive value threshold determined via a calibration operation;
• determine a subband virtual path convergence speed based on the normalized step size for each subband;
• determine a subband virtual path for each subband based on the normalized step size and the subband gradient;
• and
• apply a subband weight transformation process to each subband virtual path to update the adaptive weight filter and verify the subband virtual path.

A method comprising:

• acquiring a physical microphone signal using a physical microphone, wherein the physical microphone signal is correlated with a filtered noise signal in a vehicle cabin;
• processing the physical microphone signal with an adaptive weight filter to estimate a virtual secondary path from the physical microphone to a plurality of virtual microphones;
• acquiring a residual signal from the plurality of virtual microphones positioned in the vehicle cabin;
• decomposing the physical microphone signal and the residual signal into a plurality of subband signals;
• calculating a subband gradient for each subband based on a decomposed physical signal and a decomposed residual signal;
• calculating a normalized step size for each subband based on a power contribution of the physical microphone signal and a constant value that is adjusted based on a threshold normalized step size, the threshold normalized step size a non-zero, positive value threshold determined via a calibration operation;
• updating a set of subband virtual path weights based on the subband gradient and the normalized step size;
• weight transforming the updated set of subband virtual path weights to a time domain using an Inverse Fast Fourier Transform (IFFT);
• and
• processing the residual signal based on the transformed subband virtual weights to reduce noise in the vehicle cabin.