Spatial encoding directional microphone array
In one embodiment, an article of manufacture has microphones mounted at different locations on a non-spheroidal device body and a signal-processing system that processes the microphone signals to generate a B Format audio output having a zeroth-order beampattern signal and three first-order beampattern signals in three orthogonal directions. The signal-processing system generates at least one of the first-order beampattern signals based on effects of the device body on an incoming acoustic signal. The microphone signals used to generate each first-order beampattern signal have an inter-microphone effective distance that is less than a wavelength at a specified high-frequency value (e.g., <4 cm for 8 kHz). In preferred embodiments, the inter-microphone effective distance is less than one-half of that wavelength (e.g., <2 cm for 8 kHz). In addition, the inter-phase-center effective distances for the different first-order beampattern signals are also less than that wavelength, and preferably less than one-half of that wavelength.
1. An article of manufacture comprising:
a device body having a non-spheroidal shape;
a plurality of microphones configured at a plurality of different locations on the device body, each microphone configured to generate a corresponding microphone signal from an incoming acoustic signal; and
a signal-processing system configured to process the microphone signals to generate a first set of four different output audio signals corresponding to a zeroth-order beampattern and three first-order beampatterns in three non-planar directions, wherein:
the signal-processing system is configured to generate the output audio signal corresponding to at least one of the first-order beampatterns based on effects of the device body on the incoming acoustic signal;
for each of the non-parallel directions, the microphone signals used to generate the corresponding output audio signal have an inter-microphone effective distance that is less than a wavelength at a specified high-frequency value;
for each of the non-parallel directions, the microphone signals used to generate the corresponding output audio signal have a phase center; and
for each pair of the three non-parallel directions, an inter-phase-center effective distance between the two corresponding phase centers is less than the wavelength at the specified high-frequency value.
2. The article of claim 1 , wherein:
the specified high-frequency value is 8 kHz; and
each inter-microphone effective distance is less than 4 cm.
3. The article of claim 1 , wherein, for each of the non-parallel directions, the inter-microphone effective distance is less than half the wavelength at the specified high-frequency value.
4. The article of claim 3 , wherein:
the specified high-frequency value is 8 kHz; and
each inter-microphone effective distance is less than 2 cm.
5. The article of claim 1 , wherein:
the specified high-frequency value is 8 kHz; and
each inter-microphone effective distance and each inter-phase-center effective distance is less than 4 cm.
6. The article of claim 1 , wherein each inter-microphone effective distance and each inter-phase-center effective distance is less than half the wavelength at the specified high-frequency value.
7. The article of claim 6 , wherein:
the specified high-frequency value is 8 kHz; and
each inter-microphone effective distance and each inter-phase-center effective distance is less than 2 cm.
8. The article of claim 1 , wherein the three non-planar directions are three mutually orthogonal directions.
9. The article of claim 1 , wherein the device body has a substantially parallelepiped shape.
10. The article of claim 1 , wherein:
the plurality of microphones comprise first and second subsets of microphones;
for each of the first and second subsets of microphones, for each of the non-parallel directions, the inter-microphone effective distance is less than the wavelength at the specified high-frequency value; and
the signal-processing system is configured to generate (i) a first set of the four output audio signals based on microphone signals from the first subset of microphones and (ii) a second set of the four output audio signals based on microphone signals from the second subset of microphones, wherein the first and second sets of the four output audio signals correspond to a binaural or stereo representation of the incoming acoustic signal.
11. The article of claim 1 , wherein:
the plurality of microphones comprise first, second, third, and fourth microphones;
the first and second microphones are aligned along a first of the three non-planar directions and microphone signals from the first and second microphones are used to generate the output audio signal corresponding to the first-order beampattern in the first direction;
the third and fourth microphones are aligned along a second of the three non-planar directions and microphone signals from the third and fourth microphones are used to generate the output audio signal corresponding to the first-order beampattern in the second direction; and
microphone signals from the first and second microphones are used to generate an effective microphone signal that is used, along with microphone signals from at least one of the third and fourth microphones, to generate the output audio signal corresponding to the first-order beampattern in the third direction.
12. The article of claim 11 , wherein
the plurality of microphones further comprise fifth, sixth, seventh, and eighth microphones-;
the fifth and sixth microphones are aligned along the first direction; and
the seventh and eighth microphones are aligned along the second direction.
13. The article of claim 12 , wherein microphone signals from the fifth, sixth, seventh, and eighth microphones are used to generate a second set of four different output audio signals corresponding a zeroth-order beampattern and three first-order beampatterns in the three non-planar directions.
14. The article of claim 12 , wherein microphone signals from the fifth, sixth, seventh, and eighth microphones are used, along with the microphone signals from the first, second, third, and fourth microphones, to generate the first set of four different output audio signals.
15. The article of claim 1 , wherein:
the plurality of microphones comprise first, second, third, fourth, and fifth microphones;
the first and second microphones are aligned along a first of the three non-planar directions and microphone signals from the first and second microphones are used to generate the output audio signal corresponding to the first-order beampattern in the first direction;
the second and third microphones are aligned along a second of the three non-planar directions and microphone signals from the second and third microphones are used to generate the output audio signal corresponding to the first-order beampattern in the second direction; and
the fourth and fifth microphones are aligned along a third of the three non-planar directions and microphone signals from the fourth and fifth microphones are used to generate the output audio signal corresponding to the first-order beampattern in the third direction.
16. The article of claim 1 , wherein the signal-processing system is configured to use different subsets of the microphones to generate the output audio signals for different frequency ranges.
17. The article of claim 16 , wherein:
for acoustic signals having frequency below a specified cutoff frequency, the signal-processing system is configured to use microphones having relatively large inter-microphone effective distances to generate the output audio signals; and
for acoustic signals having frequency above the specified cutoff frequency, the signal-processing system is configured to use microphones having relatively small inter-microphone effective distances to generate the output audio signals.
18. The article of claim 16 , wherein:
for acoustic signals having frequency below a specified cutoff frequency, the signal-processing system is configured to use a larger number of the microphones to generate the output audio signals; and
for acoustic signals having frequency above the specified cutoff frequency, the signal-processing system is configured to use a smaller number of the microphones to generate the output audio signals.
19. An article of manufacture comprising:
a device body having a non-spheroidal shape;
a plurality of microphones configured at a plurality of different locations on the device body, each microphone configured to generate a corresponding microphone signal from an incoming acoustic signal; and
a signal-processing system configured to process the microphone signals to generate a first set of four different output audio signals corresponding to a zeroth-order beampattern and three first-order beampatterns in three non-planar directions, wherein:
the signal-processing system is configured to generate the output audio signal corresponding to at least one of the first-order beampatterns based on effects of the device body on the incoming acoustic signal;
for each of the non-parallel directions, the microphone signals used to generate the corresponding output audio signal have an inter-microphone effective distance that is less than a wavelength at a specified high-frequency value
the plurality of microphones comprise first and second subsets of microphones;
for each of the first and second subsets of microphones, for each of the non-parallel directions, the inter-microphone effective distance is less than the wavelength at the specified high-frequency value; and
the signal-processing system is configured to generate (i) a first set of the four output audio signals based on microphone signals from the first subset of microphones and (ii) a second set of the four output audio signals based on microphone signals from the second subset of microphones, wherein the first and second sets of the four output audio signals correspond to a binaural or stereo representation of the incoming acoustic signal.
20. An article of manufacture comprising:
a device body having a non-spheroidal shape;
a plurality of microphones configured at a plurality of different locations on the device body, each microphone configured to generate a corresponding microphone signal from an incoming acoustic signal; and
a signal-processing system configured to process the microphone signals to generate a first set of four different output audio signals corresponding to a zeroth-order beampattern and three first-order beampatterns in three non-planar directions, wherein:
the signal-processing system is configured to generate the output audio signal corresponding to at least one of the first-order beampatterns based on effects of the device body on the incoming acoustic signal;
for each of the non-parallel directions, the microphone signals used to generate the corresponding output audio signal have an inter-microphone effective distance that is less than a wavelength at a specified high-frequency value;
the plurality of microphones comprise first, second, third, and fourth microphones;
the first and second microphones are aligned along a first of the three non-planar directions and microphone signals from the first and second microphones are used to generate the output audio signal corresponding to the first-order beampattern in the first direction;
the third and fourth microphones are aligned along a second of the three non-planar directions and microphone signals from the third and fourth microphones are used to generate the output audio signal corresponding to the first-order beampattern in the second direction; and
microphone signals from the first and second microphones are used to generate an effective microphone signal that is used, along with microphone signals from at least one of the third and fourth microphones, to generate the output audio signal corresponding to the first-order beampattern in the third direction.
21. The article of claim 20 , wherein
the plurality of microphones further comprise fifth, sixth, seventh, and eighth microphones;
the fifth and sixth microphones are aligned along the first direction; and
the seventh and eighth microphones are aligned along the second direction.
22. The article of claim 21 , wherein microphone signals from the fifth, sixth, seventh, and eighth microphones are used to generate a second set of four different output audio signals corresponding a zeroth-order beampattern and three first-order beampatterns in the three non-planar directions.
23. The article of claim 21 , wherein microphone signals from the fifth, sixth, seventh, and eighth microphones are used, along with the microphone signals from the first, second, third, and fourth microphones, to generate the first set of four different output audio signals.
24. An article of manufacture comprising:
a device body having a non-spheroidal shape;
a plurality of microphones configured at a plurality of different locations on the device body, each microphone configured to generate a corresponding microphone signal from an incoming acoustic signal; and
a signal-processing system configured to process the microphone signals to generate a first set of four different output audio signals corresponding to a zeroth-order beampattern and three first-order beampatterns in three non-planar directions, wherein:
the signal-processing system is configured to generate the output audio signal corresponding to at least one of the first-order beampatterns based on effects of the device body on the incoming acoustic signal;
for each of the non-parallel directions, the microphone signals used to generate the corresponding output audio signal have an inter-microphone effective distance that is less than a wavelength at a specified high-frequency value;
the plurality of microphones comprise first, second, third, fourth, and fifth microphones;
the first and second microphones are aligned along a first of the three non-planar directions and microphone signals from the first and second microphones are used to generate the output audio signal corresponding to the first-order beampattern in the first direction;
the second and third microphones are aligned along a second of the three non-planar directions and microphone signals from the second and third microphones are used to generate the output audio signal corresponding to the first-order beampattern in the second direction; and
the fourth and fifth microphones are aligned along a third of the three non-planar directions and microphone signals from the fourth and fifth microphones are used to generate the output audio signal corresponding to the first-order beampattern in the third direction.
25. An article of manufacture comprising:
a device body having a non-spheroidal shape;
a plurality of microphones configured at a plurality of different locations on the device body, each microphone configured to generate a corresponding microphone signal from an incoming acoustic signal; and
a signal-processing system configured to process the microphone signals to generate a first set of four different output audio signals corresponding to a zeroth-order beampattern and three first-order beampatterns in three non-planar directions, wherein:
the signal-processing system is configured to generate the output audio signal corresponding to at least one of the first-order beampatterns based on effects of the device body on the incoming acoustic signal;
for each of the non-parallel directions, the microphone signals used to generate the corresponding output audio signal have an inter-microphone effective distance that is less than a wavelength at a specified high-frequency value;
the signal-processing system is configured to use different subsets of the microphones to generate the output audio signals for different frequency ranges;
for acoustic signals having frequency below a specified cutoff frequency, the signal-processing system is configured to use microphones having relatively large inter-microphone effective distances to generate the output audio signals; and
for acoustic signals having frequency above the specified cutoff frequency, the signal-processing system is configured to use microphones having relatively small inter-microphone effective distances to generate the output audio signals.
26. An article of manufacture comprising:
a device body having a non-spheroidal shape;
a plurality of microphones configured at a plurality of different locations on the device body, each microphone configured to generate a corresponding microphone signal from an incoming acoustic signal; and
a signal-processing system configured to process the microphone signals to generate a first set of four different output audio signals corresponding to a zeroth-order beampattern and three first-order beampatterns in three non-planar directions, wherein:
the signal-processing system is configured to generate the output audio signal corresponding to at least one of the first-order beampatterns based on effects of the device body on the incoming acoustic signal;
for each of the non-parallel directions, the microphone signals used to generate the corresponding output audio signal have an inter-microphone effective distance that is less than a wavelength at a specified high-frequency value;
the signal-processing system is configured to use different subsets of the microphones to generate the output audio signals for different frequency ranges;
for acoustic signals having frequency below a specified cutoff frequency, the signal-processing system is configured to use a larger number of the microphones to generate the output audio signals; and
for acoustic signals having frequency above the specified cutoff frequency, the signal-processing system is configured to use a smaller number of the microphones to generate the output audio signals.