System and method for multi-channel noise suppression
View Patent ↗Described herein are multi-channel noise suppression systems and methods that are configured to detect and suppress wind and background noise using at least two spatially separated microphones: at least one primary speech microphone and at least one noise reference microphone. The multi-channel noise suppression systems and methods are configured, in at least one example, to first detect and suppress wind noise in the input speech signal picked up by the primary speech microphone and, potentially, the input speech signal picked up by the noise reference microphone. Following wind noise detection and suppression, the multi-channel noise suppression systems and methods are configured to perform further noise suppression in two stages: a first linear processing stage that includes a blocking matrix and an adaptive noise canceler, followed by a second non-linear processing stage.
1. A system for suppressing noise in a primary input speech signal that comprises a first desired speech component and a first background noise component using a noise reference input speech signal that comprises a second desired speech component and a second background noise component, the system comprising:
a blocking matrix configured to filter the primary input speech signal in accordance with a first transfer function to estimate the second desired speech component and to remove the estimate of the second desired speech component from the noise reference input speech signal to provide an adjusted second background noise component;
an adaptive noise canceler configured to filter the adjusted second background noise component in accordance with a second transfer function to estimate the first background noise component and to remove the estimate of the first background noise component from the primary input speech signal to provide a noise suppressed primary input speech signal; and
a non-linear processor configured to apply a suppression gain to the noise suppressed primary input speech signal, wherein the suppression gain is determined based on a difference between a level of the primary input speech signal, or a signal indicative of the level of the primary input speech signal, and a level of the noise reference input speech signal, or a signal indicative of the level of the noise reference input speech signal.
2. The system of claim 1 , wherein the blocking matrix and the adaptive noise canceler are further configured to adjust a rate at which the first transfer function and the second transfer function are updated based on a presence of wind noise in the primary input speech signal.
3. The system of claim 2 , further comprising:
a wind noise detection and suppression module configured to detect the presence of wind noise in the primary input speech signal.
4. The system of claim 1 , wherein:
the blocking matrix is further configured to determine the first transfer function based on first statistics estimated from the primary input speech signal and the noise reference input speech signal, and
the adaptive noise canceler is further configured to determine the second transfer function based on second statistics estimated from the primary input speech signal and the adjusted second background noise component.
5. The system of claim 4 , wherein the blocking matrix and the adaptive noise canceler are further configured to adjust a rate at which the first statistics and the second statistics are updated based on a presence of wind noise in the primary input speech signal.
6. The system of claim 5 ,
wherein the blocking matrix and the adaptive noise canceler are further configured to halt updating the first statistics and the second statistics based on the presence of wind noise in the primary input speech signal.
7. The system of claim 1 , wherein the non-linear processor is further configured to apply the suppression gain to a single frequency component or sub-band of the noise suppressed primary input speech signal.
8. The system of claim 7 , wherein the non-linear processor is further configured to smooth the suppression gain over time and in frequency.
9. The system of claim 1 , wherein the suppression gain is adaptively adjusted based on the likelihood of desired speech.
10. The system of claim 1 , wherein the non-linear processor is further configured to determine the difference between the level of the primary input speech signal and the level of the noise reference input speech signal based on the difference between calculated signal-to-noise ratio values for the primary input speech signal and the noise reference input speech signal.
11. The system of claim 1 , further comprising:
a voice activity detector configured to detect a presence or absence of desired speech in the primary input speech signal based on a plurality of calculated speech indication values.
12. The system of claim 11 , wherein the non-linear processor is further configured to adaptively adjust the suppression gain based on whether the presence or absence of desired speech in the primary input signal was detected by the voice activity detector.
13. A method for suppressing noise in a primary input speech signal that comprises a first desired speech component and a first background noise component using a noise reference input speech signal that comprises a second desired speech component and a second background noise component, the method comprising:
filtering the primary input speech signal in accordance with a first transfer function to estimate the second desired speech component;
removing the estimate of the second desired speech component from the noise reference input speech signal to provide an adjusted second background noise component;
filtering the adjusted second background noise component in accordance with a second transfer function to estimate the first background noise component;
removing the estimate of the first background noise component from the primary input speech signal to provide a noise suppressed primary input speech signal; and
determining a suppression gain to apply to the noise suppressed primary input speech signal, wherein the suppression gain is determined based on a difference between a level of the primary input speech signal, or a signal indicative of the level of the primary input speech signal, and a level of the noise reference input speech signal, or a signal indicative of the noise reference input speech signal.
14. The method of claim 13 , wherein the first transfer function and the second transfer function are updated at a rate determined based on a presence of wind noise in the primary input speech signal.
15. The method of claim 13 , further comprising:
determining the first transfer function based on first statistics estimated from the primary input speech signal and the noise reference input speech signal, and
determining the second transfer function based on second statistics estimated from the primary input speech signal and the adjusted second background noise signal.
16. The method of claim 15 , further comprising:
adjusting a rate at which the first statistics and the second statistics are updated based on at least a presence of wind noise in the primary input speech signal.
17. The method of claim 16 , further comprising:
halting updating the first statistics and the second statistics based on the presence of wind noise in the primary input speech signal.
18. The method of claim 13 , further comprising:
applying the suppression gain to a first frequency component or a first sub-band of the noise suppressed primary input speech signal.
19. The method of claim 18 , further comprising:
smoothing the suppression gain over time and in frequency.
20. The method of claim 13 , wherein the suppression gain is adaptively adjusted based on the likelihood of desired speech.
21. The method of claim 13 , further comprising:
determining the difference between the level, of the primary input speech signal and the level of the noise reference input speech signal based on the difference between calculated signal-to-noise ratio values for the primary input speech signal and the noise reference input speech signal.
22. The method of claim 13 , further comprising:
detecting a presence or absence of desired speech in the primary input speech signal based on a plurality of calculated speech indication values.
23. The method of claim 22 , further comprising:
adaptively adjusting the suppression gain based on whether the presence or absence of desired speech in the primary input signal was detected by the voice activity detector.
24. A system for suppressing noise in a primary input speech signal that comprises a first desired speech component and a first background noise component using a noise reference input speech signal that comprises a second desired speech component and a second background noise component, the system comprising:
a blocking matrix configured to filter the primary input speech signal to estimate the second desired speech component and to remove the estimate of the second desired speech component from the noise reference input speech signal to provide an adjusted second background noise component;
an adaptive noise canceler configured to filter the adjusted second background noise component to estimate the first background noise component and to remove the estimate of the first background noise component from the primary input speech signal to provide a noise suppressed primary input speech signal; and
a non-linear processor configured to apply a suppression gain to the noise suppressed primary input speech signal determined based on the primary input speech signal and the noise reference input speech signal.