Robust adaptive noise cancelling systems and methods
Adaptive noise cancellation systems and methods comprise a reference sensor operable to sense environmental noise and generate a corresponding reference signal, an error sensor operable to sense noise in a noise cancellation zone and generate a corresponding error signal, a noise cancellation filter operable to receive the reference signal and generate an anti-noise signal to cancel the environmental noise in the cancellation zone, an adaptation module operable to receive the reference signal and the error signal and adaptively adjust the anti-noise signal, and a transient activity detection module operable to receive the reference signal, detect a transient noise event and selectively disable the adaptation module during the detected transient noise event.
1. An adaptive noise cancellation system comprising:
a reference sensor operable to sense environmental noise and generate a corresponding reference signal;
an error sensor operable to sense noise in a noise cancellation zone and generate a corresponding error signal;
a noise cancellation filter operable to receive the reference signal and generate an anti-noise signal to cancel the environmental noise in the cancellation zone;
an adaptation module operable to receive the reference signal and the error signal and adaptively adjust the anti-noise signal; and
a transient activity detection module operable to receive the reference signal, detect a transient noise event and selectively disable the adaptation module during the detected transient noise event, wherein the transient noise event is detected if a smoothed magnitude of a received signal is greater than a scaled average noise magnitude of the received signal.
2. The adaptive noise cancellation system of claim 1 wherein the transient noise event includes talking by an operator of the adaptive noise cancellation system.
3. The adaptive noise cancellation system of claim 1 wherein the transient activity detection module comprises a state machine operable to detect the transient noise event and transmit a state command to the adaptation module; and wherein the adaptation module is operable to receive the state command and enable and/or disable the adaptation in accordance therewith.
4. The adaptive noise cancellation system of claim 1 , wherein after an end of the transient noise event is detected, a delay is applied before enabling adaptation.
5. The adaptive noise cancellation system of claim 4 , wherein the end of the transient noise event is detected when the smoothed magnitude falls below the scaled average noise magnitude.
6. The adaptive noise cancellation system of claim 5 wherein the scaled average noise magnitude is derived by applying a programmable scale factor to the average noise magnitude.
7. The adaptive noise cancellation system of claim 1 wherein the noise cancellation filter is further operable to generate the anti-noise signal in accordance with stored filter coefficients; and wherein the adaptation module is further operable to modify the stored filter coefficients.
8. The adaptive noise cancellation system of claim 1 further comprising a loudspeaker operable to receive the anti-noise signal and generate anti-noise to cancel the noise in the noised cancellation zone.
9. The adaptive noise cancellation system of claim 1 wherein the adaptation module further comprises a noise amplification control subsystem.
10. The adaptive noise cancellation system of claim 1 wherein the adaptation module further comprises an adaptive gain control subsystem.
11. A method for active noise cancellation comprising:
receiving a reference signal from a first sensor, the reference signal representing external noise;
processing the reference signal through a noise cancellation filter to generate an anti-noise signal;
outputting the anti-noise signal to a loudspeaker;
receiving an error signal from a second sensor, the error signal representing noise in a noise cancellation zone;
adaptively adjusting the noise cancellation filter in response to the reference signal the, the error signal and a transient noise detection state; and
detecting a transient noise event and selectively setting the transient noise detection state to enable and disable, respectively, the adaptively adjusting the noise cancellation, wherein detecting the transient noise event comprises comparing a smoothed magnitude of the received signal to a scaled average noise magnitude of the received signal.
12. The method of claim 11 wherein the transient noise event includes talking by a user.
13. The method of claim 11 wherein selectively setting the transient noise detection state comprises transmitting a state command; and wherein the adaptively adjusting the noise cancellation filter further comprises receiving the state command and enabling and disabling, respectively, the adaptation in accordance therewith.
14. The method of claim 11 , wherein after an end of the transient noise event is detected, a delay is applied before enabling adaptation.
15. The method of claim 14 , wherein the transient noise event is detected when the smoothed magnitude falls below the scaled average noise magnitude.
16. The method of claim 15 wherein the scaled average noise magnitude is derived by applying a programmable scale factor to the average noise magnitude.
17. The method of claim 11 wherein the adaptively adjusting the noise cancellation filter comprises a noise amplification control process.
18. The method of claim 11 wherein the adaptively adjusting the noise cancellation filter comprises an adaptive gain control process.