| 摘要 |
PROBLEM TO BE SOLVED: To easily attach an acoustic resistance material when a microphone case itself is used as an acoustic tube to use a microphone unit having a larger diameter. SOLUTION: The narrowly directional microphone, which is provided with a cylindrical acoustic tube having a sound wave introduction hole, covered with the acoustic resistance material, in a tube wall, is constituted by: extending the cylindrical microphone case itself in which a unidirectional microphone unit 30 is stored toward before a front acoustic terminal of the unit by a length corresponding to a desired acoustic tube to obtain an acoustic tube portion 10C; boring the sound wave introduction hole 110 at a predetermined position of the tube wall of the acoustic tube portion 10C, forming a recessed groove 120 to form a step portion 120a on the external wall side of the acoustic tube portion 10C and around the sound wave introduction hole 110; disposing the acoustic resistance material 130 covering the sound wave introduction hole 110 at the step portion 120a; and disposing a protection net which covers the acoustic resistance material 130 and is preferably made water-repellent in the recessed groove 120. COPYRIGHT: (C)2008,JPO&INPIT
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