Variable bandwidth delayless subband algorithm for broadband active noise control system
An active noise control (ANC) system includes a speaker and one or more processors programmed to implement a delayless subband filtered-x least mean square control algorithm. The algorithm includes a variable bandwidth discrete Fourier transform filter bank having a number of subbands such that the system, in response to a broadband white noise reference signal indicative of road noise in the vehicle, exhibits a uniform gain spectrum across a frequency range defined by the subbands and partially cancels the road noise via output of the speaker.
1. An active noise control system for a vehicle comprising:
speakers;
sensors configured to detect broadband white noise reference signals indicative of road noise; and
a processor including a delayless subband filtered-x least mean square control algorithm that comprises a variable bandwidth discrete Fourier transform filter bank having a number of subbands, the processor configured to execute the delayless subband filtered-x least mean square control algorithm to process the broadband white noise reference signals and generate output exhibiting uniform gain spectrum across a frequency range defined by the subbands to partially cancel the road noise via the speakers.
2. The system of claim 1 , wherein the delayless subband filtered-x least mean square control algorithm further comprises a uniform filter bank and wherein center frequencies of the variable bandwidth discrete Fourier transform filter bank are offset from center frequencies of the uniform filter bank by one half a bandwidth of the uniform filter bank.
3. The system of claim 2 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is less than the bandwidth of the uniform filter bank.
4. The system of claim 2 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is at least one half the bandwidth of the uniform filter bank.
5. A method for actively controlling noise in an active noise control (ANC) system comprising speakers, sensors, and one or more processors including a delayless subband filtered-x least mean square control algorithm that comprises a variable bandwidth discrete Fourier transform filter bank having a number of subbands, the method comprising:
detecting by the sensors broadband white noise reference signals indicative of road noise and having an audible frequency range of 20 Hz to 20 kHz; and
executing by the one or more processors the delayless subband filtered-x least mean square control algorithm to process the broadband white noise reference signals, and generate output exhibiting uniform gain spectrum across a frequency range defined by the subbands to partially cancel the road noise via the speakers.
6. The method of claim 5 , wherein the delayless subband filtered-x least mean square control algorithm further comprises a uniform filter bank and wherein center frequencies of the variable bandwidth discrete Fourier transform filter bank are offset from center frequencies of the uniform filter bank by one half a bandwidth of the uniform filter bank.
7. The method of claim 6 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is less than the bandwidth of the uniform filter bank.
8. The method of claim 7 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is at least one half the bandwidth of the uniform filter bank.
9. An active noise control (ANC) system comprising:
a speaker;
sensors configured to detect broadband white noise reference signals indicative of road noise; and
one or more processors including a delayless subband filtered-x least mean square control algorithm that comprises a variable bandwidth discrete Fourier transform filter bank having a number of subbands, the one or more processors being configured to execute the delayless subband filtered-x least mean square control algorithm to process the broadband white noise reference signals and generate output exhibiting uniform gain spectrum across a frequency range defined by the subbands to partially cancel the road noise via the speakers.
10. The system of claim 9 , wherein the delayless subband filtered-x least mean square control algorithm further comprises a uniform filter bank and wherein center frequencies of the variable bandwidth discrete Fourier transform filter bank are offset from center frequencies of the uniform filter bank by one half a bandwidth of the uniform filter bank.
11. The system of claim 10 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is less than the bandwidth of the uniform filter bank.
12. The system of claim 10 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is at least one half the bandwidth of the uniform filter bank.