Microphone array, method and apparatus for forming constant directivity beams using the same, and method and apparatus for estimating acoustic source direction using the same

• US 20040175006A1
• Filed: 03/05/2004
• Published: 09/09/2004
• Est. Priority Date: 03/06/2003
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kong, Dong-geon, Choi, Chang-kyu, Kim, Jaywoo
• Application Number:
  US10/793,270
• Publication Number:
  US 20040175006A1
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: H04R 1/406 microphones
• CPC Class Codes: H04R 2201/401 2D or 3D arrays of transducers
• CPC Class Codes: H04R 2201/405 Non-uniform arrays of transducers or a plurality of uniform arrays with different transducer spacing
• CPC Class Codes: H04R 2430/23 Direction finding using a sum-delay beam-former
• CPC Class Codes: H04R 2430/25 Array processing for suppression of unwanted side-lobes in directivity characteristics, e.g. a blocking matrix
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A microphone array, beam forming method and apparatus using the microphone array, and a method and apparatus for estimating an acoustic source direction using the microphone array are provided. The apparatus for forming constant directivity beams comprising: a microphone array, which is comprised of first through n-th microphone sub-arrays, wherein each of the microphone sub-arrays comprises: a first microphone placed at a predetermined location on a flat plate, which commonly belongs to each of the microphone sub-arrays; and second and third microphones placed at locations perpendicularly spaced by a predetermined segment from a straight line connecting the first microphone and the center of the flat plate, the predetermined segment being determined depending on a target frequency allotted to reach of the microphone sub-arrays, a beam formation unit receiving voice signals output from the first through n-th microphone sub-arrays and generating a beam for each of the first through n-th microphone sub-arrays; a filtering unit filtering the beams output from the beam formation unit; and an adding unit adding the filtered signals output from the filtering unit.

Claims

1. A microphone array comprising:

first through n-th microphone sub-arrays,

wherein each of the microphone sub-arrays comprises;

a first microphone placed at a predetermined location on a flat plate, which commonly belongs to each of the microphone sub-arrays; and

second and third microphones placed at locations perpendicularly spaced by a predetermined segment from a straight line connecting the first microphone and the center of the flat plate, the predetermined segment being determined depending on a target frequency allotted to reach of the microphone sub-arrays.

2. The microphone array of claim 1, wherein the predetermined segment d_i can be obtained using the following equation:

3. An apparatus for forming constant directivity beams comprising:

a microphone array, which is comprised of first through n-th microphone sub-arrays,

wherein each of the microphone sub-arrays comprises;

a first microphone placed at a predetermined location on a flat plate, which commonly belongs to each of the microphone sub-arrays; and

second and third microphones placed at locations perpendicularly spaced by a predetermined segment from a straight line connecting the first microphone and the center of the flat plate, the predetermined segment being determined depending on a target frequency allotted to reach of the microphone sub-arrays.

4. The beam forming apparatus of claim 3 further comprising:

a beam formation unit receiving voice signals output from the first through n-th microphone sub-arrays and generating a beam for each of the first through n-th microphone sub-arrays;

a filtering unit filtering the beams output from the beam formation unit; and

an adding unit adding the filtered signals output from the filtering unit.

5. The beam forming apparatus of claim 4, wherein the filtering unit comprises:

a low pass filter filtering a signal having a frequency lower than the first target frequency out of the beam generated for the first microphone sub-array;

n−

2 band pass filters filtering signals in a frequency range between two adjacent target frequencies among the second through (n−

1)-th target frequencies out of the beams generated for the second through (n−

1)-th microphone sub-arrays; and

a high pass filter filtering a signal having a frequency higher than the (n−

1)-th target frequency out of the beam generated for the n-th microphone sub-array.

6. The beam forming apparatus of claim 3 further comprising:

a time/frequency conversion unit converting voice signals output from the microphones of each of the first through n-th microphone sub-arrays into frequency-domain voice signals by performing high-speed Fourier transform on the voice signals and extracting first through n-th frequency bins corresponding to the first through n-th microphone sub-arrays, respectively;

a beam formation unit receiving the first through n-th frequency bins provided by the time/frequency conversion unit and then generating beams;

a frequency bin coupling unit coupling the first through n-th frequency bins provided by the beam formation unit; and

a frequency/time conversion unit converting the result of the coupling into a time-domain beam by performing inverse high-speed Fourier transform on the output of the frequency bin coupling unit.

7. The beam forming apparatus of claim 3, wherein the predetermined segment d_i can be obtained using the following equation:

8. A method of forming constant directivity beams comprising:

(a) placing a microphone array, which is comprised of first through n-th microphone sub-arrays,

wherein each of the microphone sub-arrays comprises;

a first microphone placed at a predetermined location on a flat plate, which commonly belongs to each of the microphone sub-arrays; and

second and third microphones placed at locations perpendicularly spaced by a predetermined segment from a straight line connecting the first microphone and the center of the flat plate, the predetermined segment being determined depending on a target frequency allotted to reach of the microphone sub-arrays.

9. The beam forming method of claim 8 further comprising:

(b) forming a beam for each of the first through n-th microphone sub-arrays by receiving voice signals output from the first through n-th microphone sub-arrays;

(c) performing one of low pass filtering, band pass filtering, and high pass filtering on the beams generated in step (b) depending on their corresponding target frequencies; and

(d) adding the results of the filtering performed in step (c).

10. The beam forming method of claim 8 further comprising:

(b) converting voice signals output from the microphones of each of the first through n-th microphone sub-arrays into frequency-domain voice signals by performing high-speed Fourier transform on the voice signals and extracting first through n-th frequency bins corresponding to the first through n-th microphone sub-arrays, respectively;

(c) receiving the first through n-th frequency bins extracted in step (b) and then generating beams;

(d) coupling the beams of the first through n-th frequency bins; and

(e) converting the beam output in step (d) into a time-domain beam by performing inverse high-speed Fourier transform.

19. The method of claim 8, further comprising a computer-readable recording medium having recorded thereon a computer readable program code to form constant directivity beams using the microphone array.

11. An apparatus for estimating an acoustic source direction, comprising a microphone array, which is comprised of first through n-th microphone sub-arrays,

wherein each of the microphone sub-arrays comprises:

a first microphone placed at a predetermined location on a flat plate, which commonly belongs to each of the microphone sub-arrays; and

second and third microphones placed at locations perpendicularly spaced by a predetermined segment from a straight line connecting the first microphone and the center of the flat plate, the predetermined segment being determined depending on a target frequency allotted to reach of the microphone sub-arrays.

12. The apparatus of claim 11 further comprising:

a high-speed Fourier transform unit converting voice signals output from (2n+1) microphones into frequency-domain voice signals by performing high-speed Fourier transform on the voice signals; and

an acoustic source direction detection means detecting a peak value over all frequency ranges in a spatial spectrum provided for each frequency bin of each of the frequency-domain voice signals provided by the high-speed Fourier transform unit and then determining a direction corresponding to the detected peak value as an estimated acoustic source direction.

13. The apparatus of claim 11, wherein the predetermined segment d_i can be obtained using the following equation:

14. The apparatus of claim 12, wherein the acoustic source direction detection means comprises:

a frequency bin multiplexing unit multiplexing the frequency-domain voice signals provided by the high-speed Fourier transform unit on a frequency bin basis;

a spectrum generation unit generating spatial spectra for first through k-th frequency bins provided by the frequency bin multiplexing unit;

a spectrum coupling unit coupling the spatial spectra for the first through k-th frequency bins; and

a peak detection unit detecting a peak value in a spatial spectrum provided by the spectrum coupling unit over all frequency ranges and determining a direction corresponding to the detected peak value as an estimated acoustic source direction.

15. A method for estimating an acoustic source direction comprising:

(a) placing a microphone array, which is comprised of first through n-th microphone sub-arrays,

wherein each of the microphone sub-arrays comprises;

a first microphone placed at a predetermined location on a flat plate, which commonly belongs to each of the microphone sub-arrays; and

second and third microphones placed at locations perpendicularly spaced by a predetermined segment from a straight line connecting the first microphone and the center of the flat plate, the predetermined segment being determined depending on a target frequency allotted to reach of the microphone sub-arrays.

16. The apparatus of claim 15, wherein the predetermined segment d_i can be obtained using the following equation:

17. The method of claim 15 further comprising:

(b) converting voice signals output from (2n+1) microphones into frequency-domain voice signals by performing high-speed Fourier transform on the voice signals; and

(c) detecting a peak value over all frequency ranges in a spatial spectrum provided for each frequency bin of each of the frequency-domain voice signals obtained in step (b) and then determining a direction corresponding to the detected peak value as an estimated acoustic source direction.

18. The method of claim 17, wherein step (c) comprise:

(c1) multiplexing the frequency-domain voice signals obtained in step (b) on a frequency bin basis;

(c2) generating spatial spectra for first through k-th frequency bins that are the results of the multiplexing performed in step (c1);

(c3) coupling the spatial spectra for the first through k-th frequency bins; and

(c4) detecting a peak value in a spatial spectrum obtained as a result of the coupling performed in step (c3) coupling unit over all frequency ranges and determining a direction corresponding to the detected peak value as an estimated acoustic source direction.

20. The method of claim 15, further comprising a computer-readable recording medium having recorded thereon a computer readable program code to estimate an acoustic source direction using the microphone array.