| 摘要 |
PROBLEM TO BE SOLVED: To provide a primary sound pressure-gradient microphone which is suitable to adopt a structure where the high sensitivity side of directional characteristics in the transmission part of a portable terminal device is arranged toward a sound source at the time of speaking. SOLUTION: The CR ( the product between an acoustic capacity and an acoustic resistance) larger than that on a rear side (RSm) is set on a front side (FSm) of a primary sound pressure-gradient microphone (20) to make the rear sensitivity higher than the front sensitivity, and the microphone is used with the rear side turned toward the sound source to take out a sound signal from an output terminal (25) on the rear side. Since the high sensitivity side of the microphone is on the rear side having the output terminal, the output terminal is turned inward a casing (61) for portable terminal and cam be easily connected to a desired terminal of a circuit board (62) in the portable terminal device when the rear side as the high sensitivity side of the microphone is turned toward the sound source at the time of speaking and the front side (FSm) as the low sensitivity side is turned a rear part (RSp) of the casing (61) for portable terminal.
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