Method for phase mismatch calibration for an array microphone and phase calibration module for the same

1. A phase calibration module, calibrating phase mismatch between microphone signals output by a plurality of microphones of an array microphone, comprising:

a subband filter, extracting a high frequency component and a low frequency component from each of the microphone signals to obtain a plurality of high-frequency component signals and a plurality of low-frequency component signals;

a delay calculation module, coupled to the subband filter, for calculating delays between the low-frequency component signals; and

a delay compensation filter, coupled to the delay calculation module, for compensating the low-frequency component signals for phase mismatches therebetween according to the calculated delays to obtain a plurality of calibrated low-frequency component signals,

wherein the phase calibration module further comprises a voice activity detector, detecting whether the high-frequency component signals comprise voice components to generate a voice detection signal enabling delay calculation of the delay calculation module.

2. The phase calibration module as claimed in claim 1 , wherein the subband filter comprises a high pass filter and a low pass filter, wherein the high pass filter filters the microphone signals to obtain the high-frequency component signals according to a cutoff frequency which is equal to a boundary frequency, and the low pass filter filters the microphone signals to obtain the low-frequency component signals according to a cutoff frequency which is equal to the boundary frequency.

3. The phase calibration module as claimed in claim 2 , wherein the boundary frequency is a frequency ranging from 500 Hz to 1000 Hz.

4. The phase calibration module as claimed in claim 1 , wherein the voice activity detector detects whether powers of the high-frequency component signals exceed a power threshold to determine whether the voice detection signal is enabled.

5. The phase calibration module as claimed in claim 1 , wherein the delay calculation module correlates the low-frequency component signals to calculate the delays therebetween.

6. The phase calibration module as claimed in claim 1 , wherein combination of the high-frequency component signals and the calibrated low-frequency component signals form a plurality of calibrated signals respectively corresponding to the microphone signals, and a beamforming/signal separation module connected in series with the phase calibration module then derives a target signal without noise and interference from the calibrated signals according to beamforming or signal separation techniques.

7. A method for phase mismatch calibration for an array microphone, wherein a plurality of microphones of the array microphone convert a sound into a plurality of microphone signals, the method comprising:

extracting, by a subband filter, a high frequency component and a low frequency component from each of the microphone signals to obtain a plurality of high-frequency component signals and a plurality of low-frequency component signals;

calculating, by a delay calculation module, delays between the low-frequency component signals; and

calibrating, by a delay compensation filter, phase mismatches between the microphone signals according to the calculated delays to obtain a plurality of calibrated signals,

detecting whether the high-frequency component signals comprise voice components to generate a voice detection signal; and

enabling calculation of the delays according to the voice detection signal.

8. The method as claimed in claim 7 , wherein detection of whether the high-frequency component signals comprise voice components is determined according to whether powers of the high-frequency component signals exceed a power threshold.

9. The method as claimed in claim 7 , wherein extraction of the high-frequency component signals and the low-frequency component signals comprises:

filtering the microphone signals with a high pass filter with a cutoff frequency which is equal to a boundary frequency to obtain the high-frequency component signals; and

filtering the microphone signals with a low pass filter with a cutoff frequency which is equal to the boundary frequency to obtain the low-frequency component signals.

10. The method as claimed in claim 9 , wherein the boundary frequency is a frequency ranging from 500 Hz to 1000 Hz.

11. The method as claimed in claim 7 , wherein calculation of the delays comprises correlating the low-frequency component signals to calculate the delays therebetween.

12. The method as claimed in claim 7 , wherein calibration of the phase mismatches comprises:

compensating the low-frequency component signals for phase mismatches therebetween according to the calculated delays to obtain a plurality of calibrated low-frequency component signals,

wherein combination of the high-frequency component signals and the calibrated low-frequency component signals form the calibrated signals respectively corresponding to the microphone signals.

13. The method as claimed in claim 7 , further comprises deriving a target signal without noise and interference from the calibrated signals according to beamforming or signal separation techniques.

14. A voice processing apparatus, comprising:

an array microphone, generating a plurality of microphone signals with a plurality of microphones thereof;

a phase calibration module, coupled to the array microphone, for extracting a high frequency component and a low frequency component from each of the microphone signals to obtain a plurality of high-frequency component signals and a plurality of low-frequency component signals, calculating delays between the low-frequency component signals, and calibrating phase mismatches between the microphone signals according to the calculated delays to obtain a plurality of calibrated signals; and

a beamforming/signal separation module, coupled to the array microphone and the phase calibration module, for deriving a target signal without noise and interference from the calibrated signals according to beamforming or signal separation techniques,

wherein the phase calibration module comprises:

a subband filter, extracting the high-frequency component signals and the low-frequency component signals from the microphone signals;

a delay calculation module, calculating the delays between the low-frequency component signals; and

a delay compensation filter, compensating the low-frequency component signals for phase mismatches therebetween according to the calculated delays to obtain a plurality of calibrated low-frequency component signals;

wherein combination of the high-frequency component signals and the calibrated low-frequency component signals form the plurality of calibrated signals respectively corresponding to the microphone signals

wherein the phase calibration module further comprises a voice activity detector, detecting whether the high-frequency component signals comprise voice components to generate a voice detection signal enabling delay calculation of the delay calculation module.

15. The voice processing apparatus as claimed in claim 14 , wherein the subband filter comprises a high pass filter and a low pass filter, wherein the high pass filter filters the microphone signals to obtain the high-frequency component signals according to a cutoff frequency which is equal to a boundary frequency, and the low pass filter filters the microphone signals to obtain the low-frequency component signals according to a cutoff frequency which is equal to the boundary frequency.

16. The voice processing apparatus as claimed in claim 15 , wherein the boundary frequency is a frequency ranging from 500 Hz to 1000 Hz.

17. The voice processing apparatus as claimed in claim 14 , wherein the voice activity detector detects whether powers of the high-frequency component signals exceed a power threshold to determine whether the voice detection signal is enabled.

18. The voice processing apparatus as claimed in claim 14 , wherein the delay calculation module correlates the low-frequency component signals to calculate the delays therebetween.