Microphone array with rear venting
View Patent ↗Microphone arrays (MAs) are described that position and vent microphones so that performance of a noise suppression system coupled to the microphone array is enhanced. The MA includes at least two physical microphones to receive acoustic signals. The physical microphones make use of a common rear vent (actual or virtual) that samples a common pressure source. The MA includes a physical directional microphone configuration and a virtual directional microphone configuration. By making the input to the rear vents of the microphones (actual or virtual) as similar as possible, the real-world filter to be modeled becomes much simpler to model using an adaptive filter.
1. A method comprising:
receiving acoustic signals;
outputting microphone signals in response to receiving the acoustic signals;
controlling a delay of a first rear port of a first microphone and a second rear port of a second microphone to be approximately equal by using a common rear vent that samples a common pressure source; and
generating output signals by combining the microphone signals, the output signals including less acoustic noise than the acoustic signals;
wherein receiving acoustic signals comprises receiving acoustic signals at first and second microphones;
wherein the common rear vent comprises a common vent cavity connected to rear ports of the first and second microphones; and
wherein the common vent cavity has a volume that is small relative to a wavelength of the acoustic signals.
2. The method of claim 1 , wherein outputting microphone signals comprises outputting a first microphone output of the first microphone and a second microphone output of the second microphone.
3. The method of claim 1 , wherein the first microphone and the second microphone sample a common pressure of the vent cavity.
4. The method of claim 3 , wherein the first microphone and the second microphone have an equivalent response to the common pressure.
5. The method of claim 1 , comprising connecting the vent cavity to an external environment.
6. The method of claim 1 , comprising venting front ports of the first microphone and the second microphone to an external environment.
7. The method of claim 1 , wherein receiving acoustic signals comprises receiving acoustic signals at a first, a second and a third microphone, wherein the common rear vent comprises the third microphone.
8. The method of claim 7 , wherein outputting microphone signals comprises outputting a first virtual microphone signal by combining a first microphone output of the first microphone and a third microphone output of the third microphone.
9. The method of claim 8 , comprising subtracting the third microphone output from the first microphone output.
10. The method of claim 9 , wherein the third microphone output is delayed.
11. The method of claim 8 , wherein outputting microphone signals comprises outputting a second virtual microphone signal by combining a second microphone output of the second microphone and the third microphone output of the third microphone.
12. The method of claim 11 , comprising subtracting the third microphone output from the second microphone output.
13. The method of claim 12 , wherein the third microphone output is delayed.
14. A method comprising: receiving acoustic signals at a first microphone and a second microphone; controlling a delay of a first rear port of the first microphone to be approximately equal to a delay of a second rear port of the second microphone, wherein controlling of the delay includes venting the first rear port and the second rear port to a common vent cavity having a volume that is small relative to a wavelength of the acoustic signals; and generating output signals by combining signals from the first microphone and the second microphone, the output signals include less acoustic noise than the acoustic signals;
wherein the first microphone and the second microphone sample a common pressure of the common vent cavity; and
wherein the first microphone and the second microphone have an equivalent response to the common pressure.
15. The method of claim 14 , wherein outputting microphone signals comprises outputting a first microphone output of the first microphone and a second microphone output of the second microphone.
16. The method of claim 14 , comprising connecting the common vent cavity to an external environment.
17. The method of claim 14 , comprising venting front ports of the first microphone and the second microphone to an external environment.