JPH0834643B2 - Throat microphone - Google Patents

Description

TECHNICAL FIELD The present invention relates to a throat microphone in which howling is unlikely to occur.

2. Description of the Related Art Conventionally, electrokinetic type, electret condenser type, bone conduction type microphones and the like have been adopted and commercialized as this type of throat microphone. Here, an electret condenser type will be described as an example.

FIG. 5 shows a sectional view of a conventional electret condenser type throat microphone. In FIG. 5, 1 is a cylindrical metal case having a sound hole 1a on the top surface, 2 is a metal ring having a vibrating film 3 (electret material) formed by applying metal vapor deposition 3a on one surface, and fixed with an adhesive or the like, Reference numeral 4 is a gap spacer, 5 is a fixed electrode having a braking hole 5a, 6 is an insulator, 7 is an FET for impedance conversion, and 7a is an input terminal of the FET 7, which is electrically connected to the fixed electrode 5 by contact or spot welding. It is connected. 8 is a printed circuit board
The output terminal 7b of the FET 7 is connected and fixed by soldering 8a or the like. Each of these components is inserted into the case 1, and the end of the component is fixed to the circumference of the printed circuit board 8 by the caulking portion 1b or the like. 9 is a code for extracting this output, and 10
Is a mounting case of the metal case 1, 11 is an arm, 12 is a dustproof cloth, and 13 is skin (throat).

FIG. 6 shows an example of mounting and using this throat microphone.

Next, the operation of the above embodiment will be described. In FIG. 5, there is an air layer between the vibrating membrane 3 and the fixed electrode 5,
A capacitor (capacity) Co of about PF to several tens of PF is exhibited. this
Co changes violently when the skin 13 vibrates due to vocalization and the vibrating membrane 3 vibrates due to air transmission. If this capacitance change is ΔC, the capacitance of the capacitor is Co ^▼ = Co
It becomes ± ΔC. Therefore, the voltage change Since the capacitance change becomes a voltage change, it can be electrically taken out via the FET 7.

Microphone sensitivity Ko is Becomes (K = proportional coefficient, s = equivalent effective area of vibrating membrane 3, g = equivalent gap between vibrating membrane 3 and fixed electrode 5, Eo = surface potential of electret material) Also, sensitivity Ko is stray capacitance, C
It also depends on the gain Gv of FETs and FET7. FIG. 7 shows an equivalent circuit diagram of this conventional example.

Although the conventional example shows the type in which the electret material is used for the vibrating membrane 3, there is also a type in which the electret material is attached to the fixed electrode 5 by some method.
Further, the printed circuit board 8 is for taking out the output of the FET 7, and it is not necessary to be a separate printed circuit board, and there are a method of taking out the output terminal 7b of the FET 7 as it is, a method of taking out it through a metal terminal board or the like. The FET7 can obtain the same function even if it is externally provided without being configured internally.

However, in the above-mentioned conventional example, the vibration of the skin is transmitted to the vibrating membrane by air transmission, and because the output is taken out by this vibration, when there is a gap between the case and the skin,
Depending on the loud sound, it may cause howling. Further, there is a problem that the sound quality is greatly deteriorated.

The present invention solves such a conventional problem, and an object of the present invention is to provide a throat microphone in which howling is less likely to occur and sound quality is less deteriorated.

Means for Solving the Problems The present invention is a cylindrical metal case having a hole on the top surface to achieve the above object, a fixed electrode in which the polymer film is electretized in the metal case, and of the FET An insulator that holds the input terminal together with the fixed electrode and insulates it from the metal case, a printed circuit board that fixes the output terminal of the FET, and a protection that is arranged between the hole on the top surface of the metal case and the fixed electrode. And a film, which has a structure in which the metal case or a plate covering the metal case is in close contact with the throat.

Action The present invention has the following actions due to the above-mentioned configuration. That is, a capacitor is formed between the skin and the metal fixed electrode, and the change in skin vibration is grasped by the change in capacitance, and the built-in FET
Can be converted into an electric signal and taken out.

Embodiment FIG. 1 shows the configuration of an embodiment of the present invention.
The same parts as those in FIG. 5 are indicated by the same numbers.

In FIG. 1, 21 is a cylindrical metal case having a hole 21a, 25 is a metal fixed electrode to which a polymer film 25b is attached by heat fusion or an adhesive, and 25a is a braking hole. The insulator 6, the FET 7 and the printed circuit board 8 are the same as the conventional ones, and these internal parts are inserted into the metal case 21,
The end of the metal case 21 is caulked around the circumference of the printed circuit board 8.
It is fixed by 21b etc. Reference numeral 30 denotes a mounting case for the metal case 21, and 34 denotes a metal plate, which is electrically connected to the metal case 21. The metal plate 34 need not be provided as long as the metal case 21 directly contacts the skin 13.

In the above structure, the polymer film 25b is electretized by some method. Therefore, a FEP film or the like is suitable as a material for the polymer film 25b.

FIG. 2 shows an electric equivalent circuit of FIG.
A capacitor Co ₁ is formed between the metal fixed electrodes 25 of the skin 13. The skin 13 is not a perfect conductive object but has a certain amount of conductive voice, so it may be considered as an equivalent circuit of the same figure.

When the skin 13 vibrates due to vocalization, the capacitance of the capacitor Co ₁ changes. Therefore, it can be taken out as a voltage change as in the conventional case.

As described above, according to the above-described embodiment, the vibration of the skin 13 is conventionally vibrated by vibrating the vibrating membrane 3 by air transmission. That is,
According to the present invention, the change of the skin 13 is directly recognized as a capacitance change, but the capacitance change is extracted as a highly sensitive electric signal by using the electric charge (surface potential) of the electret. Have an effect.

In the above example, the skin 13 is not completely conductive,
Although it has a drawback that it is more susceptible to induced noise (hum, etc.) than the hole 21a, a method of removing or reducing it with a filter using an electric circuit may be considered. Alternatively, two microphones may be connected in parallel, one for vibration detection and the other for inductive noise cancellation.

FIG. 3 (a) shows a general use example of a throat microphone, in which the output of the microphone is taken out through an equalizer. That is, it is effective in correcting the transmission loss due to the skin 13 and reproducing more faithfully. FIG. 6B is an example showing the frequency-gain characteristics of the equalizer.

FIG. 4 is a sectional view showing another embodiment. This is because the electret may be deteriorated due to the attachment of water, dust, etc., so that the thin film protective film 35 for drip-proofing is formed on the front surface side of the metal fixed electrode 25. In this embodiment, the metal ring 36 is adhered and fixed to the metal ring 36 by some method, and the spacers 37 are arranged on the front surface of the metal fixed electrode 25.

As the protective film 35, a conductive one constitutes an electret condenser microphone and operates abnormally, so that a film having a high insulating property is desirable.

Various methods can be considered in addition to the configuration example of the protective film 35 provided for the purpose of preventing the electret from being deteriorated as described above. For example, the spacer 37 is abolished, and the protective film 35 and the metal ring 36 are configured in the opposite manner to that shown in FIG.

Although not shown in this embodiment, the microphone of the present invention may be configured at both ends of the mounting arm 11 to take the sum of the two, and in this case, the sound can be more surely amplified. .

Although the throat microphone of the present invention has been described above, various applications such as heart sound detection and sphygmomanometer are conceivable from the viewpoint of directly detecting the vibration of the skin 13.

Effects of the Invention As apparent from the above examples, since the change in skin vibration is directly recognized as the change in capacitance of the capacitor, the vibration of the vibration source itself can be directly converted into an electric signal, so that the sound quality is less deteriorated and the moisture is protected by the protective film. It is possible to prevent the fixed electrode from being deteriorated due to adhesion of dust or the like. Further, since the metal case or the plate covering the metal case is configured to be in close contact with the throat, there is an effect that howling is unlikely to occur even if there is a gap between the attachment portion and the skin.

[Brief description of drawings]

1 is a sectional view of a throat microphone showing an embodiment of the present invention, FIG. 2 is an electrical equivalent circuit diagram in FIG. 1, and FIG.
FIG. 4 is a diagram showing an example of using the throat microphone, FIG. 4 is a sectional view showing another embodiment of the present invention, FIG. 5 is a sectional view showing a conventional throat microphone, and FIG. 6 is a mounting diagram of the throat microphone. , FIG. 7 is an electrical equivalent circuit diagram in FIG. 21 …… Metal case, 25 …… Metal fixed electrode, 25b …… Polymer film, 6 …… Insulator, 7 …… FET, 8 …… Printed circuit board, 30 …… Mounting case, 34 …… Metal plate,
9 ... Output extraction cord, 11 ... Arm, 13 ... Skin.

Claims (1)

[Claims] 1. A metal case having a tubular metal case having a hole on the top surface, a fixed electrode located in the metal case and having a polymer film made into an electret, and an input terminal of an FET together with the fixed electrode. Insulator to insulate with FET and FET
A printed circuit board for fixing the output terminals of the device, and a protective film disposed between the hole on the top surface of the metal case and the fixed electrode, and adheres to the throat by the metal case or a plate covering the metal case. A throat microphone having the structure described below.