| 摘要 |
PROBLEM TO BE SOLVED: To provide a capacitor microphone suitable for detection of low frequency audio signals with an inexpensive configuration.SOLUTION: A capacitor microphone includes: a vibration film subassembly 20 in which a vibration film 22 is fixed to an undersurface of a holding ring 20; a back electrode plate and a spacer disposed underneath the vibration film subassembly 20; and a conductive cover 50 for covering them from the above. The conductive cover 50 is disposed on the upper wall so as to closely attached to an upper surface 24a of the holding ring 24. As a ventilation structure for maintaining an equilibrium between a back pressure at the lower side of the vibration film 22 in the conductive cover 50 and the external air pressure, a groove 24g extending over the upper surface 24a of the holding ring 24 in circumferential direction is provided, the groove 24 having one end part 24g1 opening into an inner peripheral surface side of the holding ring 24 and the other end part 24g2 opening into an outer peripheral surface side thereof. Thereby, a moderate flow resistance is provided without additional components so that the detection of low frequency acoustic signals is not adversely affected. |
