Virtual microphone array systems using dual omindirectional microphone array (DOMA)
View Patent ↗A dual omnidirectional microphone array noise suppression is described. Compared to conventional arrays and algorithms, which seek to reduce noise by nulling out noise sources, the array of an embodiment is used to form two distinct virtual directional microphones which are configured to have very similar noise responses and very dissimilar speech responses. The only null formed is one used to remove the speech of the user from V 2 . The two virtual microphones may be paired with an adaptive filter algorithm and VAD algorithm to significantly reduce the noise without distorting the speech, significantly improving the SNR of the desired speech over conventional noise suppression systems.
1. A system comprising:
a microphone array including a first physical microphone outputting a first microphone signal and a second physical microphone outputting a second microphone signal;
a processing component coupled to the microphone array and generating a virtual microphone array comprising a first virtual microphone and a second virtual microphone, the first virtual microphone comprising a first combination of the first microphone signal and the second microphone signal and having a first linear response to speech and a first linear response to noise, the first linear response to speech being substantially similar across a plurality of frequencies for a speech source located within a predetermined angle relative to an axis of the microphone array, the second virtual microphone comprising a second combination of the first microphone signal and the second microphone signal, the second virtual microphone having a second linear response to speech and a second linear response to noise, the second linear response to noise being substantially similar to the first linear response to noise, one or both of the first linear response to noise and the second linear response to noise being non-zero in a direction toward a source of noise, and the second linear response to speech being substantially dissimilar to the first linear response to speech, wherein the second combination is different from the first combination; and
an adaptive noise removal application coupled to the processing component and generating denoised output signals by forming a plurality of combinations of signals output from the first virtual microphone and the second virtual microphone, wherein the denoised output signals include less acoustic noise than acoustic signals received at the microphone array.
2. The system of claim 1 , wherein the first and second physical microphones are omnidirectional.
3. The system of claim 1 , wherein the first linear response to speech is devoid of a null, wherein the speech is human speech.
4. The system of claim 3 , wherein the second linear response to speech includes a single null oriented in a direction toward a source of the speech.
5. The system of claim 4 , wherein the single null is a region of the second linear response to speech having a measured response level that is lower than the measured response level of any other region of the second linear response to speech.
6. The system of claim 4 , wherein the second linear response to speech includes a primary lobe oriented in a direction away from the source of the speech.
7. The system of claim 6 , wherein the primary lobe is a region of the second linear response to speech having a measured response level that is greater than the measured response level of any other region of the second linear response to speech.
8. The system of claim 4 , wherein the first physical microphone and the second physical microphone are positioned along an axis and separated by a first distance.
9. The system of claim 8 , wherein a midpoint of the axis is a second distance from the speech source that generates the speech, wherein the speech source is located in a direction defined by an angle relative to the midpoint.
10. The system of claim 9 , wherein the first virtual microphone comprises the second microphone signal subtracted from the first microphone signal.
11. The system of claim 10 , wherein the first microphone signal is delayed.
12. The system of claim 11 , wherein the delay is raised to a power that is proportional to a time difference between arrival of the speech at the first virtual microphone and arrival of the speech at the second virtual microphone.
13. The system of claim 11 , wherein the delay is raised to a power that is proportional to a sampling frequency multiplied by a quantity equal to a third distance subtracted from a fourth distance, the third distance being between the first physical microphone and the speech source and the fourth distance being between the second physical microphone and the speech source.
14. The system of claim 10 , wherein the second microphone signal is multiplied by a ratio, wherein the ratio is a ratio of a third distance to a fourth distance, the third distance being between the first physical microphone and the speech source and the fourth distance being between the second physical microphone and the speech source.
15. The system of claim 9 , wherein the second virtual microphone comprises the first microphone signal subtracted from the second microphone signal.
16. The system of claim 15 , wherein the first microphone signal is delayed.
17. The system of claim 16 , wherein the delay is raised to a power that is proportional to a time difference between arrival of the speech at the first virtual microphone and arrival of the speech at the second virtual microphone.
18. The system of claim 16 , wherein the power is proportional to a sampling frequency multiplied by a quantity equal to a third distance subtracted from a fourth distance, the third distance being between the first physical microphone and the speech source and the fourth distance being between the second physical microphone and the speech source.
19. The system of claim 18 , wherein the first microphone signal is multiplied by a ratio, wherein the ratio is a ratio of the third distance to the fourth distance.
20. The system of claim 1 , wherein the first virtual microphone comprises the second microphone signal subtracted from a delayed version of the first microphone signal.
21. The system of claim 20 , wherein the second virtual microphone comprises a delayed version of the first microphone signal subtracted from the second microphone signal.
22. The system of claim 1 , comprising a voice activity detector (VAD) coupled to the processing component, the VAD generating voice activity signals.
23. The system of claim 1 , comprising a communication channel coupled to the processing component, the communication channel comprising at least one of a wireless channel, a wired channel, and a hybrid wireless/wired channel.
24. The system of claim 23 , comprising a communication device coupled to the processing component via the communication channel, the communication device comprising one or more of cellular telephones, satellite telephones, portable telephones, wireline telephones, Internet telephones, wireless transceivers, wireless communication radios, personal digital assistants (PDAs), and personal computers (PCs).
25. A system comprising:
a first virtual microphone formed from a first combination of a first microphone signal and a second microphone signal, wherein the first microphone signal is generated by a first physical microphone and the second microphone signal is generated by a second physical microphone;
a second virtual microphone formed from a second combination of the first microphone signal and the second microphone signal, wherein the second combination is different from the first combination,
wherein the first virtual microphone has a first linear response to speech and first linear response to noise, the first linear response to speech being substantially similar across a plurality of frequencies for a speech source located within a predetermined angle relative to an axis of the microphone array and devoid of a null, wherein the second virtual microphone has a second linear response to speech that has a single null oriented in a direction toward a source of the speech and a second linear response to noise, wherein the second linear response to noise is substantially similar to the first linear response to noise, one or both of the first linear response to noise and the second linear response to noise being non-zero in a direction toward a source of noise, and the second linear response to speech is substantially dissimilar to the first linear response to speech, wherein the speech is human speech; and
an adaptive noise removal application coupled to the first and second virtual microphones and generating denoised output signals by forming a plurality of combinations of signals output from the first virtual microphone and the second virtual microphone, wherein the denoised output signals include less acoustic noise than acoustic signals received at the first and second physical microphones.
26. The system of claim 25 , wherein the single null is a region of the second linear response to speech having a measured response level that is lower than the measured response level of any other region of the second linear response to speech.
27. The system of claim 25 , wherein the second linear response to speech includes a primary lobe oriented in a direction away from the source of the speech.
28. The system of claim 27 , wherein the primary lobe is a region of the second linear response to speech having a measured response level that is greater than the measured response level of any other region of the second linear response to speech.
29. A system comprising:
a first microphone outputting a first microphone signal and a second microphone outputting a second microphone signal, wherein the first microphone and the second microphone are omnidirectional microphones;
a virtual microphone array comprising a first virtual microphone and a second virtual microphone, wherein the first virtual microphone comprises a first combination of the first microphone signal and the second microphone signal and has a first linear response to speech and a first linear response to noise, the first linear response to speech being substantially similar across a plurality of frequencies for a speech source located within a predetermined angle relative to an axis of the microphone array, wherein the second virtual microphone comprises a second combination of the first microphone signal and the second microphone signal and has a second linear response to speech and a second linear response to noise, the second linear response to noise being substantially similar to the first linear response to noise, one or both of the first linear response to noise and the second linear response to noise being non-zero in a direction toward a source of noise, and the second linear response to speech being substantially dissimilar to the first linear response to speech, wherein the second combination is different from the first combination, wherein the first virtual microphone and the second virtual microphone are distinct virtual directional microphones; and
an adaptive noise removal application coupled to the virtual microphone array and generating denoised output signals by forming a plurality of combinations of signals output from the first virtual microphone and the second virtual microphone, wherein the denoised output signals include less acoustic noise than acoustic signals received at the first microphone and the second microphone.
30. A system comprising:
a first physical microphone generating a first microphone signal;
a second physical microphone generating a second microphone signal;
a processing component coupled to the first microphone signal and the second microphone signal, the processing component generating a virtual microphone array comprising a first virtual microphone and a second virtual microphone, the first virtual microphone having a first linear response to speech and a first linear response to noise, the first linear response to speech being substantially similar across a plurality of frequencies for a speech source located within a predetermined angle relative to an axis of the microphone array, the second virtual microphone having a second linear response to speech and second linear response to noise, the second linear response to noise being substantially similar to the first linear response to noise, one or both of the first linear response to noise and the second linear response to noise being non-zero in a direction toward a source of noise, and the second linear response to speech being substantially dissimilar to the first linear response to speech,
wherein the first virtual microphone comprises the second microphone signal subtracted from a delayed version of the first microphone signal,
wherein the second virtual microphone comprises a delayed version of the first microphone signal subtracted from the second microphone signal; and
an adaptive noise removal application coupled to the processing component and generating denoised output signals, wherein the denoised output signals include less acoustic noise than acoustic signals received at the first physical microphone and the second physical microphone.
31. The system of claim 30 , wherein the first linear response to speech is devoid of a null, wherein the speech is human speech.
32. The system of claim 31 , wherein the second linear response to speech includes a single null oriented in a direction toward a source of the speech.
33. The system of claim 32 , wherein the single null is a region of the second linear response to speech having a measured response level that is lower than the measured response level of any other region of the second linear response to speech.
34. The system of claim 32 , wherein the second linear response to speech includes a primary lobe oriented in a direction away from the source of the speech.
35. The system of claim 34 , wherein the primary lobe is a region of the second linear response to speech having a measured response level that is greater than the measured response level of any other region of the second linear response to speech.
36. The system of claim 32 , wherein the first physical microphone and the second physical microphone are positioned along an axis and separated by a first distance.
37. The system of claim 36 , wherein a midpoint of the axis is a second distance from the speech source that generates the speech, wherein the speech source is located in a direction defined by an angle relative to the midpoint.
38. The system of claim 37 , wherein one or more of the first microphone signal and the second microphone signal is delayed.
39. The system of claim 38 , wherein the delay is raised to a power that is proportional to a time difference between arrival of the speech at the first virtual microphone and arrival of the speech at the second virtual microphone.
40. The system of claim 39 , wherein the power is proportional to a sampling frequency multiplied by a quantity equal to a third distance subtracted from a fourth distance, the third distance being between the first physical microphone and the speech source and the fourth distance being between the second physical microphone and the speech source.
41. The system of claim 37 , wherein one or more of the first microphone signal and the second microphone signal is multiplied by a gain factor.
42. The system of claim 30 , comprising a voice activity detector (VAD) coupled to the processing component, the VAD generating voice activity signals.
43. The system of claim 30 , comprising a communication channel coupled to the processing component, the communication channel comprising at least one of a wireless channel, a wired channel, and a hybrid wireless/wired channel.
44. The system of claim 43 , comprising a communication device coupled to the processing component via the communication channel, the communication device comprising one or more of cellular telephones, satellite telephones, portable telephones, wireline telephones, Internet telephones, wireless transceivers, wireless communication radios, personal digital assistants (PDAs), and personal computers (PCs).
45. A system comprising:
a physical microphone array including a first physical microphone and a second physical microphone, the first physical microphone outputting a first microphone signal and the second physical microphone outputting a second microphone signal;
a virtual microphone array comprising a first virtual microphone and a second virtual microphone, the first virtual microphone comprising a first combination of the first microphone signal and the second microphone signal and having a first linear response to speech and a first linear response to noise, the first linear response to speech being substantially similar across a plurality of frequencies for a source of speech located within a predetermined angle relative to an axis of the microphone array, the second virtual microphone comprising a second combination of the first microphone signal and the second microphone signal and having a second linear response to speech and a second linear response to noise, the second linear response to noise being substantially similar to the first linear response to noise, one or both of the first linear response to noise and the second linear response to noise being non-zero in a direction toward a source of noise, and the second linear response to speech being substantially dissimilar to the first linear response to speech, wherein the second combination is different from the first combination and the virtual microphone array includes a single null oriented in a direction toward the source of speech of a human speaker; and
an adaptive noise removal application coupled to the virtual microphone array and generating denoised output signals by forming a plurality of combinations of signals output from the virtual microphone array, wherein the denoised output signals include less acoustic noise than acoustic signals received at the physical microphone array.
46. The system of claim 45 , wherein the first linear response to speech is devoid of a null, wherein the second linear response to speech includes the single null.
47. The system of claim 46 , wherein the single null is a region of the second linear response to speech having a measured response level that is lower than the measured response level of any other region of the second linear response to speech.
48. The system of claim 46 , wherein the second linear response to speech includes a primary lobe oriented in a direction away from the source of the speech.
49. The system of claim 48 , wherein the primary lobe is a region of the second linear response to speech having a measured response level that is greater than the measured response level of any other region of the second linear response to speech.
50. The system of claim 45 , wherein the single null is located at a distance from the physical microphone array where the source of the speech is expected to be.
51. A system comprising:
a first virtual microphone comprising a first combination of a first microphone signal and a second microphone signal, the first virtual microphone having a first linear response to speech and a first linear response to noise, the first linear response to speech being substantially similar across a plurality of frequencies for a speech source located within a predetermined angle relative to an axis of the microphone array, wherein the first microphone signal is output from a first physical microphone and the second microphone signal is output from a second physical microphone;
a second virtual microphone comprising a second combination of the first microphone signal and the second microphone signal, the second virtual microphone having a second linear response to speech and a second linear response to noise, the second linear response to noise being substantially similar to the first linear response to noise, one or both of the first linear response to noise and the second linear response to noise being non-zero in a direction toward a source of noise, and the second linear response to speech being substantially dissimilar to the first linear response to speech, wherein the second combination is different from the first combination, wherein the first virtual microphone and the second virtual microphone are distinct virtual directional microphones; and
a processing component coupled to the first and second virtual microphones, the processing component including an adaptive noise removal application receiving acoustic signals from the first virtual microphone and the second virtual microphone and generating an output signal, wherein the output signal is a denoised acoustic signal.