United States Patent  [li] Patent Number: 4,703,506
Sakamoto et al.  Date of Patent: Oct. 27, 1987
 DIRECTIONAL MICROPHONE APPARATUS
 Inventors: Atsushi Sakamoto; Makoto Iwahara, both of Sagamihara, Japan
 Assignee: Victor Company of Japan, Ltd., Japan
 Appl. No.: 888,057
 Filed: Jul. 22, 1986
 Foreign Application Priority Data
Jul. 23, 1985 [JP] Japan 60-162572
 Int. CI.4 H04R 3/00
 U.S. CI 381/92; 367/125;
 Field of Search 367/121, 126, 123, 125;
381/92, 122, 26
 References Cited
U.S. PATENT DOCUMENTS
4,025,894 5/1977 Ziese 367/126
4,485,484 11/1984 Flanagan 381/92
4,536,887 8/1986 Kaneda et al 381/92
FOREIGN PATENT DOCUMENTS
56-08994 1/1981 Japan 381/92
59-149494 8/1984 Japan .
OTHER PUBLICATIONS S. Ibaraki et al: "2nd-Order Gradient Microphone Al
ley" Acoustic Research Lab. Matsushita Elec. Ind. Co., Ltd.; Mar. 1984.
Yoshihiko, ABE et al: "Practical Application and Digital Control of the Microphone Array"; AES, Presented at the 76th Convention 1984 Oct. 8-11, New York.
Primary Examiner—Forester W. Isen
Attorney, Agent, or Firm—Lowe, Price, Leblanc, Becker
A directional microphone apparatus includes an array of at least three sets of microphone units, circuits for processing the output signals from the microphone units to produce a first signal which varies in accordance with the second order bidirectional sound pressure gradient characteristic of the array, weighting circuits for applying respective weighting coefficients to the output signals from the microphone units in accordance with a desired shape of directivity response characteristic, to produce corresponding weighted signals which are combined to form a second signal. The first and second signals are combined to produce an output signal which exhibits sharp directivity even at relatively low frequencies in the audio range.
10 Claims, 17 Drawing Figures