JPS58182397A - Magnetic bone conduction microphone - Google Patents

Abstract

PURPOSE:To obtain a microphone stable in the operating point and excellent in the acoustic characteristics, by synthesizing the magnetic bone conduction microphones of velocity and acceleration type. CONSTITUTION:A diaphragm 17 is made of resin or metal film having concentric ruggedness and low in the intensity of resonance and the resonance point is scattered. A suspension 14 is made of a metallic plate having a high molecules of rigidity to improve the linearity and to attain low attenuation and formed into a shape allowing sufficient stroke. In contacting an outer skin contact chip 15 on the surface of a living body, the suspension 14 is swollen toward the diaphgram 17, but the diaphragm 17, a magnet 20 and a magnet core 19 are displaced in the same direction by the equal amount. Thus, even if the pressing force is changed, the operating point is unchanged. In transmitting a bone conduction sound to the chip 15, the suspension 14 acts like an HPF to deliver the high frequency components to the diaphragm 17. The oscillation of the suspension 14 is transmitted to the diaphragm 17 almost without loss as mentioned above. In this case, a moving coil 18 only is oscillated and an electric signal with fidelity is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electromagnetic bone conduction microphone that converts into bone conduction electrical signals and is effective in 4IK under high noise conditions.

As conventional electromagnetic bone conduction microphones, speed plate and acceleration type are known. Figure lm1 shows an example of a speed plate electromagnetic bone conduction microphone. In the figure, 1 is the magnetic core,
2 is a power generation coil, 3 is a permanent monument, and the power generation section is made of straw.

A suspension 4 is attached to the frame of the magnetic core 1 with screws 5, and an outer skin contact chip 7 with an imaging plate 6 made of a magnetic material is fixed to the suspension 4. In addition,
This fixation occurs on one side lζ diaphragm 6 of the suspension 4.
This is done by placing the skin contact chip 7 on the other side and screwing the male thread formed on the diaphragm 6Iζ into the female thread formed on the skin contact chip 7.

In the speed reduction microphone having such a configuration, when the surface of the living body vibrates due to bone conduction sound, this vibration is directly transmitted to the skin contact tip 7 and the diaphragm 6. Therefore, it has the advantage of being able to directly pick up vibrations and convert them into electrical signals.

However, since the diaphragm 6 directly contacts the surface of the living body via the skin contact tip 7, there is a drawback that the operating point changes depending on the pressure applied to the living body. In addition, when the microphone is pressed against the headband or the like, the sound of contact with the headpan F and the sound of a strike are easily picked up. Increasing the rigidity of the suspension to prevent these problems had the disadvantage of reducing output. Furthermore, it is easy to pick up low-frequency sounds in the living body, such as sounds of blood flow and pulsation, and the noise becomes a noise component.

Therefore, there was a drawback that SA was poor. Furthermore, since the suspension of the power generation mechanism is exposed to the outside air and is susceptible to common loss, it has the disadvantage that air noise is relatively easily picked up and howling is likely to occur.

Next, an example of a conventional acceleration type electromagnetic bone conduction microphone will be explained with reference to FIG. In the figure, 8 is the main body case,
9 is a lid attached to the main body case 8 with screws. Further, the suspension 4 is sandwiched between the main body case 8 and the fi9, and the central portions of the suspension 4 and the diaphragm 10 are fixed to each other by 8tI. Further, a diaphragm 6 made of a magnetic material is attached to the center of the diaphragm 10. Note that the symbols other than these indicate the same or equivalent items as in FIG. 1.

Now, in the acceleration bone conduction microphone having such a configuration, the entire main body case 8 attached to the surface of the living body vibrates in response to bone conduction sound. This vibration causes the diaphragm 6 to vibrate through the suspension 4. At this time, the magnetic core 122 and the permanent magnet 3 do not move because their diameter is large and the moment of inertia is large, and only the diaphragm 1θ moves. Therefore, the distance between the diaphragm 6 and the convex portion of the magnetic core 1 changes, and the bone conduction lid is converted into an electrical signal.

This type of microphone has the advantage that the operating point does not change at all even if the pressure applied to the living body changes. However, since the transmission mechanism of the lid is complicated, there are many differential losses and absorption, and it has the disadvantage that it is difficult to pick up natural snow. In other words, the sound quality changes and the individuality of the voice is suppressed.
8, there was a drawback that the sound of the transmission system itself was added.

Furthermore, in this type of microphone, the power generation mechanism is not directly exposed to the outside air, and the main body case, lid, and suspension have high rigidity, so howling is relatively less likely to occur than in the above-mentioned speed type. However, when used in a high noise environment, the speaker sound is generally loud and the diaphragm is large, so external noise reaches the diaphragm. In this case, since the vibration system of this type of microphone is formed only by the diaphragm, vibration occurs at the resonance point of the diaphragm, and /% ringing occurs. Therefore, it was not suitable as a microphone for a public address system under high noise conditions.

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, to avoid changing the operating point due to the pressure applied to the living body, to pick up low frequency noise, to be resistant to shock noise, and to pick up natural sounds. The aim is to provide a transverse bone conduction microphone that is effective under high noise conditions. Another object of the present invention is to provide a non-howling microphone that can be used even under high noise conditions.

The characteristics of the present invention include a main body case, a suspension that is attached to the main body case and is made of a metal plate with high rigidity and good linearity and has a shape that allows a sufficient stroke, an outer skin contact tip fixed to the center of the suspension, The central part includes a diaphragm fixed to the skin contact tip, a power generation mechanism supported only by the diaphragm, and converting the vibration of the diaphragm into an electric signal.

Another advantage is that the mosquito diaphragm and the two-boo vibration system of the suspension each have greatly different resonance points, and each is coupled with a metal material whose acoustic resistance can be ignored.

The present invention will be explained below by way of examples. FIG. 3 shows an embodiment of the invention. As is clear from the figure, the main body 12 is fixed to the main body case 11 with screws 13 8r'I. A suspension 14 is sandwiched between the lid 12 and the main case 11. 11 in the center of the suspension 14. By screwing the male screw 16 into the female screw provided on the skin contact tip 15 via the suspension 14,
A skin contact tip 15 is fixed. Excellent male screw 1
Reference numeral 6 is a metal material having a thickness and hardness that allows negligible acoustic resistance, and its head is fixed to a diaphragm 17 made of a non-magnetic material by adhesive or the like. A moving coil 18 is attached to this die and diaphragm 17.

On the other hand, a permanent magnet 20 is fixed to the magnetic core 19,
The convex portion of the magnetic core 19 projects inside the winding of the movable coil 18 . The permanent magnet 20 is connected to the diaphragm by a support member 21 having a plurality of air holes 22 around the periphery of the diaphragm.
tII. Also, fit12 and suspension 14
A damper 23 made of a sponge or the like is provided between the two. 24 is a lead wire for taking out an electric signal, specifically, an air hole 22 provided in the support member 21.
2 and the main body case 11 to take it out to the outside.

Here, the diaphragm 17 is formed of a resin film or a metal film provided with concentric irregularities. Therefore, the diaphragm 17 can reduce the strength of resonance at the resonance points and disperse the resonance points. Further, the movable coil 18 attached to the diaphragm 17 can easily move independently of the permanent magnet 20.

FIG. 4 is a plan view of the suspension 14. The suspension 14 is made of a metal plate with high rigidity, such as a steel plate, in order to improve linearity and reduce damping against vibrations on the biological surface. It is made so that the center part has sufficient variation @ (stroke) with respect to the peripheral part. In the figure, 141 is a metal plate, 14b is a punched portion, and 14c is a screw insertion hole.

The suspension 14 and the diaphragm 17 are made of materials, thicknesses, and shapes such that their self-resonance frequencies are greatly different.

Further, FIG. 5 is a plan view of the support member 21. As shown in FIG.

The support member 21 is provided with air holes 22 on a plurality of sides.

Next, the operation of this embodiment will be explained. First, the microphone shown in FIG. 3 is pressed against the surface of a living body with a pressure force of several hundred grams or less, using the skin contact tip 15 as a contact surface, using a headband or Herad set. Then, as described above, since the suspension 14 has a shape that allows a sufficient stroke, the suspension 14 swells into the diaphragm 17g4 in response to the pressing force.

However, the deformation of the diaphragm during pressure welding is in the low frequency range, so the diaphragm 17. The magnet 20 and the magnetic core 19 supported by this also change their position by the same amount in the same direction at the same time as the magnet 20 and the magnetic core 19 are compressed. Therefore, even if the force with which the microphone is pressed against the living body surface changes, the operating point does not change.

Now, bone conduction spreads from the voice to the bone tissue and subcutaneous tissue,
Assuming that the sound is transmitted to the surface of the living body, vibrations based on the bone conduction sound are transmitted to the skin contact tip 15I that is in pressure contact with the surface of the living body. In this case, since the suspension 14 has a high resistance, it acts as a bypass filter, cuts out the low frequency component (1), and transmits the high frequency component to the diaphragm 17.The diaphragm 17 resists vibration as described above. The vibration of the suspension 14 is transmitted to the diaphragm 17 with almost no loss because it is made of a small material and has a shape that reduces resistance.When the diaphragm 17 vibrates, the diaphragm 17.magnetic core 19 Air in the space surrounded by the permanent magnet 20 and the support member 21 flows in and out through a plurality of air holes 22 provided in the support member 21.

On the other hand, since the masses of the magnetic core 19 and the permanent magnet 20 are large, this moment of inertia is large. Therefore, when vibration is transmitted from the living body side to the diaphragm 17 as described above, the moving coil 16 vibrates, but the magnetic core 19 and the permanent stone 20 do not vibrate. As a result, the movable coil 18 moves within the field created by the permanent magnet 20, and an electric signal corresponding to the vibration is generated in the movable coil 18.

The electric signal generated in the moving coil 18 passes through the lead wire 24 and exits to the terminal at the subsequent stage.

The microphone of this embodiment does not cause howling even when used as a loudspeaker microphone under high noise conditions.

The details will be explained below. Generally, in the microphone of this embodiment, the mechanical impedance of the suspension gene 14 is sufficiently higher than that of the air, resulting in mismatching, and the amount of air is difficult to be transmitted to the diaphragm 17 in a normal atmosphere.

However, in environments where the speakers are used in high-noise environments, the speaker sound is generally loud and the noise is large.
The sound travels around the suspension 14 and diaphragm 17 a little before reaching the sound. However, in this embodiment, as mentioned above, since the self-resonance frequencies of the suspension 14 and the diaphragm 17 are significantly different, the amount that wraps around and reaches the suspension 14 and the diaphragm 17 is the first The vibration system, that is, the moment of inertia of the magnetic core 19 and the permanent magnet 20 with respect to the suspension 14 prevents resonance of the suspension,
The diaphragm does not vibrate easily. suspension 14
Even if it resonates despite ζtI#c, it is difficult to induce resonance because the resonance point of the diaphragm 17, which is the second internal vibration system, is different from the resonance point of the suspension 14. Therefore, the microphone of this embodiment can be said to have a structure that is extremely resistant to howling.

As described above, in this embodiment, even when the microphone is pressed against both surfaces of a 4-year-old living body, the operating point does not change, and the noise is low and does not interfere. Therefore, all the drawbacks of the conventional speed lever microphone as described above can be eliminated. In this example, the magnetic core 19 and the permanent monument 2
The moment of inertia at zero is so great that the stiffener does not move, but the diaphragm 1γ that holds the moving coil 18 vibrates. Therefore, although it performs an acceleration type operation, the diaphragm 17K directly transmits vibrations on the surface of the living body, so it is able to peak up more natural sounds than conventional acceleration type microphones.

Further, since the suspension 14 has a large difference in mechanical impedance from the air, the sound insulation of the air volume is large. For this reason, it is extremely effective for calls under high noise environments.

In addition, by sufficiently separating the number of resonances between the suspension 14 and the diaphragm 17, the effect of the suspension 14 is combined with the sound effect of the Suspension 14, and even if the output of the speaker etc. is returned to the microphone for a long time, the sound will not be heard. The target combination is unobtrusive and the howling is extremely unpleasant. According to the inventor's experiment 4ζ, using the microphone of Example C, the output of the speaker was 130 d at the microphone position (In).
Howling did not occur even when the sound pressure was increased to B. Therefore, even if the output of the speaker is increased to a level that allows sufficient transmission under high noise conditions 1c, howling does not occur and a great effect is exhibited under high noise conditions.

According to this embodiment, the shot noise applied to the main body case IIK is absorbed by the suspension 14 that is in pressure contact with the living body, and the subcutaneous tissue that is roughly under pressure functions as a damper material with high hysteresis. Since the vibration is damped, the effect on the power generation mechanism is extremely small.

Furthermore, the damper 23's action of 1tK can attenuate unnecessary sounds caused by the self-collinearity of the suspension 14 itself when the case is struck, for example, in front of the air, when the damper 23 is not in pressure contact with the living body. Therefore, it is insensitive to external ilK. However, when the microphone is in a living body [f:*, the mass and impedance of the bone tissue are both large, so the suspension 14 is forcibly vibrated by the bone vibration sound Cζ regardless of the damping of the damper 23. It will be done. Therefore, it is possible to obtain sufficient pickup sound.

Another embodiment of the present invention is shown in Figure 6. This example is the third
The difference from the illustrated embodiment is that a movable iron piece 2s is attached to the diaphragm 17 instead of the movable coil 18,
and the generating coil 26 is the magnetic core 19 KWjA518rI
The rest of the structure is the same as or equivalent to Volume 3.

In addition to this implementation S, when the movable iron piece 2z moves in response to bone conduction sound, the movable iron piece 2s, the magnetic core 1 and the permanent stone 2
0, and the resistance of the magnetic circuit changes at once.

For this reason, the bundle passing through the power generation coil 26 is oxidized, and the vibration is converted into an electric signal.

The effect of this embodiment is almost the same as that of Fig. 3, so
Explanation will be omitted.

As described above, since the present invention has a configuration that combines a velocity type electromagnetic bone conduction microphone and an acceleration type electromagnetic bone conduction microphone, the operating point is stable, low frequency noise is not picked up, and the It has a large ratio and can pick up natural sounds. Furthermore, since it is insensitive to external noise, it does not pick up noise or cause howling even when used under high noise conditions. Therefore, it is suitable as a microphone under high noise environments.

[Brief explanation of the drawing]

Figure 1 shows the conventional straight 11! I Newspaper diagram of an example of an electromagnetic bone conduction microphone, No. 2111 is a cross-sectional view of an example of a conventional acceleration type electromagnetic bone conduction microphone, FIG. 3 is a cross-sectional view of an example of the present invention, and FIG. Used as an example, 1000 WIM of Giwadai Suspension, #I! 11ll is a plan view of the support member 8t'I used in this embodiment, and Figure 6 is a newspaper diagram of another embodiment of the present invention. 11... Main body case, 12... Lid, 14... Suspension, 1B... Outer skin contact tip, 17... Diaphragm, 18... Moving coil, 19... Magnetic core, 2°... Permanent - stone, 21... support member, 2-toe air hole,
23... Damper, 24... Lead wire, 2 To... Movable iron piece, 2... Power generation filter, Sanjin valve, Hiraki Michi, 1 non-human

Claims (2)

[Claims] (1) Main body case, a suspension made of metal with high rigidity and good linearity attached to the main body case, and a shape that allows for sufficient stroke, a skin contact tip fixed to the center of the mosquito suspension, and a cough skin in the center. An electromagnetic bone conduction microphone characterized by comprising a diaphragm fixed to a contact tip, a power generation mechanism supported only by the diaphragm, and converting vibrations of the wrinkled diaphragm into electrical signals. (2) Paragraph 1 of the Patent Enclosure, characterized in that the power generation mechanism is comprised of a moving coil fixed to the center of the diaphragm, and a permanent magnet and a magnetic core fixed to one side of the cough diaphragm via a support member. The electromagnetic moving coil bone conduction microphone described. +31 In 11, the power generation mechanism is characterized by comprising a movable iron piece fixed to the central part of the diaphragm, and a permanent magnet, a magnetic core, and a power generation coil fixed to the peripheral part of the cough diaphragm via a support member. An electromagnetic moving magnet bone conduction microphone according to claim 1.