Dual omnidirectional 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 device comprising:
a headset including at least one loudspeaker, wherein the headset attaches to a region of a human head, the headset including a first area and a second area at which to dispose a first physical microphone and a second physical microphone, respectively, the first physical microphone being disposed at least an intra-microphone distance from the second physical microphone, the intra-microphone distance being less than a dimension of the headset;
a microphone array connected to the headset, the microphone array including the first physical microphone outputting a first microphone signal and the second physical microphone outputting a second microphone signal, and the first physical microphone and the second physical microphone forming an axis of the microphone array; and
a processing component coupled to the microphone array and configured to generate a virtual microphone array comprising a first virtual microphone and a second virtual microphone of which at least one is based on the intra-microphone distance, the first virtual microphone comprising a first combination of the first microphone signal and the second microphone signal, the second virtual microphone comprising 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 and the second virtual microphone have substantially similar responses to noise and substantially dissimilar responses to speech, and wherein the second virtual microphone is configured to generate an output signal in response to a speech signal received at the microphone array, the output signal in response to the speech signal being zero when the speech signal is received substantially along the axis of the microphone array, and to generate an output signal in response to a noise signal received at the microphone array, the output signal in response to the noise signal not being zero when the noise signal is received substantially along the axis of the microphone array.
2. The device of claim 1 , wherein the first and second physical microphones are omnidirectional.
3. The device of claim 1 , wherein the first virtual microphone has a first linear response to speech that is devoid of a null, wherein the speech is human speech.
4. The device of claim 3 , wherein the second virtual microphone has a second linear response to speech that includes a single null oriented in a direction toward a source of the speech.
5. The device of claim 4 , wherein the single null is a region of the second linear response having a measured response level that is lower than the measured response level of any other region of the second linear response.
6. The device of claim 4 , wherein the second linear response includes a primary lobe oriented in a direction away from the source of the speech.
7. The device of claim 6 , wherein the primary lobe is a region of the second linear response having a measured response level that is greater than the measured response level of any other region of the second linear response.
8. The device 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 device of claim 8 , wherein a midpoint of the axis is a second distance from a 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 device of claim 9 , wherein the first virtual microphone comprises the second microphone signal subtracted from the first microphone signal.
11. The device of claim 10 , wherein the first microphone signal is delayed.
12. The device 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 device 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 device 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 device of claim 9 , wherein the second virtual microphone comprises the first microphone signal subtracted from the second microphone signal.
16. The device of claim 15 , wherein the first microphone signal is delayed.
17. The device 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 device 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 device 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 device 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 device 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 device of claim 1 , wherein a speech source that generates the speech is a mouth of a human wearing the headset.
23. The device of claim 1 , comprising a voice activity detector (VAD) coupled to the processing component, the VAD generating voice activity signals.
24. The device of claim 1 , comprising an adaptive noise removal application coupled to the processing component, the adaptive noise removal application receiving signals from the first and second virtual microphones and generating an output signal, wherein the output signal is a denoised acoustic signal.
25. The device of claim 24 , wherein the microphone array receives acoustic signals including acoustic speech and acoustic noise.
26. The device 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.
27. The device of claim 26 , comprising a communication device coupled to the headset 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).
28. A device comprising:
a housing;
a loudspeaker connected to the housing;
a first physical microphone and a second physical microphone connected to the housing, which includes a first area and a second area at which to dispose the first physical microphone and the second physical microphone, respectively, the first physical microphone being disposed at least an intra-microphone distance from the second physical microphone, the intra-microphone distance being less than a dimension of the housing, the first physical microphone outputting a first microphone signal and the second physical microphone outputting a second microphone signal, wherein the first and second physical microphones are omnidirectional, and wherein the first physical microphone and the second physical microphone form an axis;
a first virtual microphone comprising a first combination of the first microphone signal and the second microphone signal; and
a second virtual microphone comprising 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 and the second virtual microphone are distinct virtual directional microphones with substantially similar responses to noise and substantially dissimilar responses to speech,
wherein at least one of the first virtual microphone and the second virtual microphone is based on the intra-microphone distance, and
wherein the second virtual microphone is configured to generate an output signal in response to a speech signal received at the first physical microphone and the second physical microphone, the output signal in response to the speech signal being zero when the speech signal is received substantially along the axis formed by the first physical microphone and the second physical microphone, and to generate an output signal in response to a noise signal received at the first physical microphone and the second physical microphone, the output signal in response to the noise signal not being zero when the noise signal is received substantially along the axis formed by the first physical microphone and the second physical microphone.
29. A device comprising:
a housing including a loudspeaker, wherein the housing is portable and configured for attaching to a mobile object; and
a physical microphone array connected to the headset, the physical microphone array including a first physical microphone and a second physical microphone that form a virtual microphone array comprising a first virtual microphone and a second virtual microphone, and the physical microphone array having an axis formed by the first physical microphone and the second physical microphone;
the first virtual microphone comprising a first combination of a first microphone signal and a second microphone signal, wherein the first microphone signal is generated by the first physical microphone and the second microphone signal is generated by the second physical microphone; and
the second virtual microphone comprising 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 that is 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, wherein the speech is human speech, and wherein the second virtual microphone is configured to generate an output signal in response to a speech signal received at the physical microphone array, the output signal in response to the speech signal being zero when the speech signal is received substantially along the axis of the physical microphone array, and to generate an output signal in response to a noise signal received at the physical microphone array, the output signal in response to the noise signal not being zero when the noise signal is received substantially along the axis of the physical microphone array.
30. The device of claim 29 , wherein the first virtual microphone and the second virtual microphone have a linear response to noise that is substantially similar.
31. The device of claim 29 , wherein the single null is a region of the second linear response having a measured response level that is lower than the measured response level of any other region of the second linear response.
32. The device of claim 29 , wherein the second linear response includes a primary lobe oriented in a direction away from the source of the speech.
33. The device of claim 32 , wherein the primary lobe is a region of the second linear response having a measured response level that is greater than the measured response level of any other region of the second linear response.
34. A device comprising:
a housing that is attached to a region of a human speaker;
a loudspeaker connected to the housing; and
a physical microphone array including a first physical microphone and a second physical microphone connected to the housing, the first physical microphone outputting a first microphone signal and the second physical microphone outputting a second microphone signal that in combination form a virtual microphone array, and the physical microphone array having an axis formed by the first physical microphone and the second physical microphone;
the 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, the second virtual microphone comprising a second combination of the first microphone signal and the second microphone signal, wherein the second combination is different from the first combination;
the virtual microphone array including a single null oriented in a direction toward a source of speech of the human speaker; and
wherein the second virtual microphone is configured to generate an output signal in response to a speech signal received at the physical microphone array, the output signal in response to the speech signal being zero when the speech signal is received substantially along the axis of the physical microphone array, and to generate an output signal in response to a noise signal received at the physical microphone array, the output signal in response to the noise signal not being zero when the noise signal 1 is received substantially along the axis of the physical microphone array.
35. The device of claim 34 , wherein the first virtual microphone has a first linear response to speech that is devoid of a null, wherein the second virtual microphone has a second linear response to speech that includes the single null.
36. The device of claim 35 , wherein the first virtual microphone and the second virtual microphone have a linear response to noise that is substantially similar.
37. The device of claim 35 , 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.
38. The device of claim 35 , wherein the second linear response to speech includes a primary lobe oriented in a direction away from the source of the speech.
39. The device of claim 38 , wherein the primary lobe is a region of the second linear response having a measured response level that is greater than the measured response level of any other region of the second linear response.
40. The device of claim 34 , wherein the single null is located at a distance from the physical microphone array where the source of the speech is expected to be.