PURPOSE: To reduce the adverse effect due to change in the humidity by forming an insulating layer on the surface of a fixed electrode of the titled electrostatic acoustic transducer comprising the fixed electrode made of a metallic disc through which lots of holes are made and a moving electrode made by evaporating a metal on a plastic.
CONSTITUTION: The insulating layer 5 made of an insulating material such as "Teflon", fluororesin or the like is formed on the surface of the fixed electrode 2 made by making lots of holes 1 through the metallic disc. A diaphragm 3 made of a plastic is fitted by clipping the insulating layer 5 and the moving electrode 4 is formed by vapor-depositing a metal on the upper surface of the diaphragm 3. A DC bias voltage is applied to both the electrodes 2, 4 via a resistor R and an AC power supply (e) in, e.g., 50∼60kHz is connected via a capacitor C for performing electroacoustic conversion. Thus, the reduction in the sensitivity and the rate of change in the capacitance due to humidity change are decreased.
INOUE HIROMITSU
AZUMA NAOYA
