Microphone system

• US 6,069,961 A
• Filed: 11/06/1997
• Issued: 05/30/2000
• Est. Priority Date: 11/27/1996
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakazawa, Fumihiko
• Primary Examiner(s): Chang, Vivian
• Assistant Examiner(s): Lemm, Debra A.
• Application Number:
  US08/965,191
• Time in Patent Office: 936 Days
• Field of Search: 381/92, 381/122, 367/124, 367/126
• US Class Current: 381/92
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

Provided is a microphone system capable of detecting a direction of a sound source and extracting an object sound with a high S/N ratio. A microphone system comprises a plurality of microphone pairs 1 to 7, each pair having two microphones arranged apart from each other at a predetermined space at a crossing angle of 60 degrees or less, a plurality of subtraction circuits 11a for calculating a difference signal of outputs of each microphone pair, a plurality of addition circuits 11e for calculating a sum signal of outputs of each microphone pair, circuit sections 11c, 11d and 20 for detecting, as sound source direction information, a minimum value output from each output of the subtraction circuits 11a, and a switch 11f for selecting a sum signal of the microphone pairs 1 to 7 corresponding to the minimum value output and for outputting the selected sum signal as sound information.

Claims

1. A microphone system comprising:

a plurality of microphone pairs, each pair having two microphones arranged apart from each other at a predetermined space at a crossing angle of 60 degrees or less;

a plurality of first calculating means for calculating a difference signal of outputs of each microphone pair;

a plurality of second calculating means for calculating a sum signal of outputs of each microphone pair;

means for detecting, as sound source direction information, a minimum value output from each output of the first calculating means; and

means for selecting a sum signal of the microphone pair corresponding to the minimum value output and outputting the selected sum signal as sound information.

2. The microphone system according to claim 1, wherein a sum signal corresponding to a second smallest difference signal is also selected and output in addition to the sum signal corresponding to the minimum value of the difference signal.

3. The microphone system according to claim 1, wherein a plurality of microphone pairs are arranged on a concentric circle.

4. The microphone system according to claim 1, further comprising a low-pass filter for filtering the difference signal output from the first calculating means at a cut-off frequency F represented by V/2D=F between a sound velocity V and the space D.

7. The microphone system according to any of claims 1 to 6, wherein the microphone is a non-directional microphone.

8. The microphone system according to claim 7, wherein the sound source is provided on a central axis of a microphone array, thereby adjusting a sensitivity of each microphone pair.

5. A microphone system comprising:

a microphone array in which microphone sets are arranged at a crossing angle of 45 degrees or less, each microphone set including a first microphone pair having two microphones arranged apart from each other at a predetermined space and a second microphone pair orthogonal to the first microphone pair;

a plurality of first calculating means for calculating a difference signal of outputs of each microphone pair;

means for detecting, as a direction of a sound source, a minimum value output from each output of the first calculating means;

second calculating means for calculating a ratio of output voltages of a microphone pair orthogonal to a microphone pair corresponding to the minimum value output; and

means for calculating a distance from the microphone array to a sound source based on the ratio of the output voltages which is calculated by the second calculating means.

6. A microphone system comprising a plurality of sound source direction discriminators including a plurality of microphone pairs, each pair having two microphones arranged apart from each other at a predetermined space at a crossing angle of 60 degrees or less, a plurality of calculating means for calculating a difference signal of outputs of each microphone pair, and means for detecting, as a direction of a sound source, a minimum value output from each output of the calculating means, wherein a crossing point of the directions of the sound source which are obtained by the sound source direction discriminators is calculated, thereby detecting a position of the sound source.