JPS59117400A - Electrostatic acoustic transducer - Google Patents

Abstract

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.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called cell type electrostatic acoustic transducer.

FIG. 1 shows a configuration diagram of a conventional cell-type electrostatic acoustic transducer. (2) is a disk-shaped fixed electrode, and this fixed electrode (2) is made of a metal such as aluminum or brass, or a molded product with a metal coated or vapor-deposited for one conductivity. Further, this fixed electrode (2) K has a large number of holes (+) for allowing sound waves to pass through. (3
) l/'i This is a vibrating membrane formed on the upper surface of the fixed electrode (2), and is formed by this vibrating membrane + 31 t/'i. Shake again! On the upper surface of the 4IJ film (3), a flexible wJ electrode (4) is provided, which is made of metal vapor-deposited on the surface of plastic. Between the movable electrode (4) and the fixed electrode (2), there is a DC power source E that provides a DC bias via a resistor R, and a DC power source E that provides a vibration of frequency 50 to 60) G (z) via a cosidecisor C. Here, when a DC bias is applied by the DC power source E and an AC voltage is applied from the AC power source e, the vibrating membrane (3) vibrates and the hole ( 1) It is designed to output more sound waves.In the electrostatic acoustic transducer 4 having such a configuration, the second
As shown in FIG. 3 and FIG. 3, there was a problem in that the capacitance and sensitivity changed when the humidity changed. That is, when the temperature increases from lo to 20 inches to 100% Kf, the sensitivity changes by about 5 dB as shown in FIG. 2, and the capacitance change rate also changes by 20 inches.

The present invention has been provided in view of the above-mentioned points, and provides an electrostatic acoustic transducer whose purpose is to reduce changes in capacitance value and sensitivity due to changes in humidity.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 4 shows a cross-sectional view, and the structure is substantially the same as that of the conventional example. The die, which is different from the conventional one, is that an insulating layer (5) made of an insulating material such as a differential and fluororesin is formed on the entire surface of the fixed electrode (2) (including the inner circumferential surface of the hole (1)). be. Further, the insulating layer (5) may be provided on the surface of the fixed electrode (2) that contacts the vibrating membrane (3) and on the inner peripheral surface of the hole f+1. By configuring the fixed electrode (2) as shown in FIG. 4, the sensitivity change and the change in humidity with respect to humidity are as shown in FIGS. 5 and 6. In other words, as shown in Figure 5, the sensitivity change is approximately 2.5 d.
B, the change can be suppressed to about 1/2 or less compared to the conventional one, and the capacitance change rate is about 2% as shown in Figure 6, which is about 1/2 compared to the conventional one! OK, it can be suppressed.

As described above, in the electrostatic acoustic transducer of the present invention, by forming an insulating layer on the surface of the fixed electrode, the change in temperature sensitivity can be suppressed to about 1/2 or less compared to the conventional one. Further, the capacitance change with respect to temperature can be suppressed to about 1/10.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional electrostatic acoustic transducer, Figure 2 is a characteristic diagram of humidity and sensitivity change as above, Figure 3 is a characteristic diagram of humidity layer and capacitance change rate as above, FIG. 4 is a cross-sectional view of an embodiment of the present invention, FIG. 5 is a characteristic diagram of humidity and sensitivity change same as above, and FIG.
The figure is a characteristic diagram of the rate of change of humidity and volume. (1) is a hole, (2) is a solid W electrode, (3) is a vibrating membrane, (4
) indicates a movable electrode, and (5) indicates an insulating layer. Agent Patent Attorney Ishi 1) Choshichi

Claims (1)

[Claims] [1] A vibrating membrane is provided on a fixed electrode with many holes for allowing sound waves to pass through, a movable electrode is provided on the surface of the vibrating membrane, and an electric signal is applied between the movable electrode and the fixed electrode. An electrostatic acoustic transducer configured to output sound waves through holes in a fixed electrode, the electrostatic acoustic transducer comprising an insulating layer formed on the surface of the fixed electrode.