JP2001218297A - Contact-type microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact-type microphone that can pick up a very small vibration sound with a sound pressure level of about several dBs in air, even under a normal environment, provides a sufficiently superior output S/N used for broadcasting and a high output voltage which does not need a special post- stage amplifier. SOLUTION: The contact type microphone is provided with a stylus contact pin 10, whose tip is in contact with a vibrating object and an electroacoustic transducer 11 that transduces vibration delivered to the contact pin into an electrical signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact microphone for picking up a minute vibration sound of an object with high sensitivity.

[Summary of the Invention] [0002] The present invention relates to a microphone that picks up a minute vibration sound of an object with high sensitivity, and pays attention to the fact that an object radiating sound always vibrates. A contact microphone that directly contacts a thin and light needle-shaped contact pin and converts vibration transmitted to the contact pin into an electric signal is realized. Unlike a normal microphone, since it does not have a vibrating membrane, it does not pick up sound in the air that propagates in the air in the environment where the microphone is installed.
Further, it is possible to collect only a small vibration sound of a target object with high sensitivity without being affected by background noise in a normal use environment.

[0003]

2. Description of the Related Art A method for picking up minute vibration sound of an object includes:
There is a method of collecting the propagation sound in the air using a normal microphone having a vibrating membrane, and a method of collecting the sound by directly taking out the vibration of the object and converting it into electricity.

In general, when a very small sound having a very low sound pressure is picked up using a microphone, both the intrinsic noise of the microphone and the intrinsic noise of the post-amplifier must be sufficiently low. In addition, the background noise level of the picking up environment must also be sufficiently low.

For example, when the sound pressure level emitted from an object is 10
If the sum of the input converted sound pressure levels of these three noises is not sufficiently lower than 10 dB, the sound emitted from the target object has a lower level than the noise, and the sound buried in the so-called noise Will be.

[0006] Some microphones used for acoustic measurement have a negative input conversion of the inherent noise, but the microphone output at the time of noise measurement is large in low and high ranges close to human hearing. In general, correction is performed using the A characteristic, which has an attenuating characteristic. If the correction is not performed using the A characteristic, the noise level increases.

[0007]

However, when sound is picked up by a microphone, correction of the A characteristic is not usually performed.

[0008] Further, when a minute sound is targeted, an environment having a background noise level of several dB or less, that is, an anechoic room or the like is required. It can not be used except in small environments.

[0009] Further, since the sensitivity of a microphone intended for a minute sound is increased, the background noise is also large.

[0010] For these reasons, it has been very difficult to pick up a minute sound from the air using the vibration of the air under a normal environment using the conventional technology.

Therefore, it is considered that the method of directly extracting the vibration of the object and converting it into an electric signal is optimal for collecting the minute vibration sound of the object which is the subject of the present invention. It was difficult to realize using the technique described above.

First, there is a record needle as a device for converting vibration into an electric signal. However, a record needle is not suitable as a transducer for minute vibration as the object of the present invention.

That is, since a large driving force and weight are applied to the record needle, a mechanism having low compliance such as rubber is generally used as a supporting mechanism. For this reason, the frequency range in which the needle can follow the minute vibration is narrowed, and at the same time, the output is also small, and cannot be adopted. In addition,
The reason why the frequency range at the time of record reproduction is wide is that the driving force for the record needle is sufficiently large.

Further, since the entire magnetic circuit of the record needle is made small, the coils constituting the magnetic circuit are very small. Therefore, the electric converted output is very small. In order to amplify to the level used in broadcasting, the gain of the post-amplifier needs to be very large, and it is difficult to sufficiently satisfy the S / N.

Next, there is a vibration pickup used for general measurement purposes as a device for converting vibration into an electric signal. Although a piezoelectric element is often used for this vibration pickup, the input-equivalent noise of the piezoelectric element is much larger than that of an electrodynamic type, so that the piezoelectric element cannot be used for applications against minute vibration.

In addition, a piezoelectric element for converting vibration into an electric signal is provided in the housing. Vibration from the outside is first transmitted to the housing, and vibration of the housing is transmitted to the piezoelectric element. For this reason, a loss occurs in the vibration transmitted to the piezoelectric element. That is, a mechanism for directly transmitting vibration to the piezoelectric element is required, but there is no vibration pickup having such a mechanism.

The present invention has been made in view of the above circumstances, and enables sound having a sound pressure level of about several dB in air to be collected even under a normal environment, and the S / N of the output is broadcast. It is an object of the present invention to provide an ultra-sensitive contact type microphone which is sufficiently high enough to be used for an electronic device and has a large output voltage so as not to require a special post-amplifier.

[0018]

According to a first aspect of the present invention, there is provided a contact-type microphone according to the first aspect of the present invention, comprising: a needle-shaped contact pin which is in contact with an object whose tip vibrates; An electroacoustic transducer for converting vibration transmitted to the pin into an electric signal.

According to this configuration, only the vibration transmitted through the needle-like contact pin is converted into electricity and collected, and almost no sound propagating in the air is collected. Sound can be picked up without being affected by background noise.

According to a second aspect of the present invention, there is provided the contact type microphone according to the first aspect, further comprising a damper mechanism for attenuating transmission of vibration of an installed environment to the contact pin. It is characterized by:

According to this configuration, the vibration of the environment installed by the damper mechanism can be suppressed from being transmitted to the contact pins, and the sensitivity can be increased.

According to a third aspect of the present invention, in the contact type microphone according to the first or second aspect, the entirety of the contact pin and the electro-acoustic transducer is integrally formed with the length of the contact pin. And an adjusting mechanism for moving in the vertical direction.

According to this configuration, the contact state of the contact pins can be adjusted according to the shape of the object, and reliable contact can be realized.

According to a fourth aspect of the present invention, in the contact type microphone according to any one of the first to third aspects, a supporting pin for supporting an object to be placed is provided. It is characterized by having.

According to this configuration, the overload on the contact pin can be reduced, and reliable contact with the object can be realized.

According to a fifth aspect of the present invention, in the contact type microphone according to any one of the first to fourth aspects, the electroacoustic transducer generates a constant magnetic field. It is of an electrodynamic type including a circuit and a coil movably arranged in the constant magnetic field with the vibration of the contact pin.

According to this configuration, since the size of the coil is not limited as in the case of the record needle, it can be made large enough to obtain a large electric output. The use of an amplifier becomes possible.

According to a sixth aspect of the present invention, in the contact type microphone according to the fifth aspect, the contact pin and the coil for electrically converting vibration of the contact pin are formed in a thin film shape. It is characterized by being supported by a spring member.

According to this configuration, the compliance of the mechanical vibration system can be increased, so that it has a wide frequency characteristic with respect to minute vibrations and can increase the output voltage.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic sectional view of a contact microphone which is an embodiment of an electrodynamic electroacoustic transducer according to the present invention.

In FIG. 1, the contact type microphone according to the present embodiment includes a microphone unit 1 and a pedestal 2 having a concave cross section for housing and supporting the microphone unit 1.

As shown in FIG. 2, the microphone unit 1 has a contact pin 10 provided on an electrodynamic electroacoustic transducer 11, which will be described in detail later.

A weight support pin 3 is provided upright on the upper end surface of the side wall of the pedestal 2. This weight support pin 3 is shown in FIG.
In FIG. 2, the object supporting plate 4 is mounted as needed. Depending on the shape of the object, the object may be directly placed without the object support plate 4.

The weight supporting pin 3 is desirably made of a hard material with a small internal loss. Since the vibration of the object support plate 4 and the vibration of the directly placed object are transmitted to the contact pins 10 without loss, the contact area with the object support plate 4 and the directly placed object is smaller. Is good. In the illustrated example, the shape is such that contact close to point contact is possible.

The object support plate 4 is a plate that supports the weight of the object. In order to transmit the vibration of the object to the contact pin 10 without loss, the object support plate 4 is preferably made of a hard material having a small internal loss as described above.

A foot 6 is attached to the lower end surface of the side wall of the pedestal 2 via an anti-vibration spring 5. Anti-vibration spring 5
Is provided to attenuate unnecessary vibration from the floor so as not to be transmitted to the pedestal 2. The feet 6 are provided to stably support the entire contact microphone of the present embodiment on the installation floor. The whole of the vibration-proof spring 5 and the foot 6 corresponds to the damper mechanism according to the second aspect.

Further, a height adjusting screw 7 is attached to the center of the floor of the pedestal 2 (corresponding to the adjusting mechanism of claim 3). The height adjusting screw 7 is screwed from the outer surface (the lower surface in the illustrated example) of the floor of the pedestal 2 toward the inside of the pedestal 2. Thereby, the height adjusting screw 7 can push up the bottom of the microphone unit 1.

Therefore, the contact pins 10 of the microphone unit 1 can be brought into contact with the object support plate 4 with an appropriate pressure in the example of FIG. 1 by adjusting the amount of pushing up by the height adjusting screw 7.

When the height adjusting screw 7 is rotated in the reverse direction by rotating the height adjusting screw 7 in reverse, the microphone unit 1 descends by its own weight and settles on the floor of the pedestal 2.

FIG. 2 is a sectional view for explaining details of the microphone unit 1. The microphone unit 1 has a needle-shaped contact pin 10 whose tip comes into contact with an object to extract the vibration of the object, and an electrokinetic electroacoustic conversion that converts the vibration of the object extracted by the contact pin 10 into an electric signal. Table 11
It is composed of

The contact pin 10 is preferably made of a material having a small internal loss, and the smaller the contact area at the tip, the better. In the illustrated example, the needle has a thin and light needle shape capable of making contact close to point contact.

The electrodynamic electroacoustic transducer 11 includes an E-shaped magnetic body 111 constituting an iron core, a magnet 112 attached to an outer frame (outer leg) of the magnetic body 111, and a middle frame of the magnetic body 111. (Inner leg), a coil 113 that moves up and down integrally with the attached contact pin 10 and outputs the vibration as an electric signal,
And a thin film-shaped spring 114 movably supported in a magnetic circuit formed by the magnet 112.

Next, the operation of the contact microphone according to the present embodiment will be described with reference to FIGS.

An object (not shown) that emits sound is placed on the object support plate 4. When the object vibrates on the object support plate 4, the vibration is transmitted to the contact pins 10 through the object support plate 4, and the contact pins 10 vibrate vertically. Then, the coil 113 moves up and down integrally with the contact pin 10, cuts off a constant magnetic field in the magnetic circuit formed by the magnetic body 111 and the magnet 112, and outputs an electric signal.

The above is a case where the object is placed on the object support plate 4. Depending on the shape of the object, the object support plate 4 may be omitted and the object may be directly connected to the weight support pins 3. Of course, it may be put on top.

At this time, the vibration transmitted from the floor to the foot 6 is suppressed by the vibration-proof spring 5, and is hardly transmitted to the contact pin 10. Further, the contact pin 10 is not sensitive to the vibration of air. Therefore, the electric signal output from the coil 113 corresponds to only the magnitude of the vibration extracted from the object by the contact pin 10.

Since the size of the coil 113 is not limited as in the case of a record needle, it is possible to make the coil 113 large enough to obtain a large electric output. Thus, a commonly used microphone amplifier can be used.

Further, since the spring 114 supporting the contact pin 10 and the coil 113 for converting the vibration of the contact pin 10 is made of a thin film member, the compliance of the mechanical vibration system can be increased, and Has a wide frequency characteristic, and can increase the output voltage.

As described above, the contact type microphone according to the present embodiment is hardly affected by the vibration of the surrounding environment or the vibration transmitted through the air, and the contact pin 10 is in contact with the object.
Can convert only vibrations into electricity, and can collect minute vibration noises with ultra-high sensitivity. Therefore, it is suitable for sound pickup of minute vibration of the vibrating body in a normal environment.

The electro-acoustic transducer includes an electrostatic type and a piezoelectric type in addition to the electrodynamic type. The contact type microphone having the electrodynamic electroacoustic transducer in the present embodiment has been described for the following two reasons.

That is, first, since the input-converted inherent noise level is generally the smallest in the electrodynamic type, in order to capture minute vibrations, it is necessary to use the electrodynamic electroacoustic transducer. This is because it is desirable.

Second, in the electrostatic type and the piezoelectric type,
Since the impedance of the converter is high, a conversion circuit is required to reduce the impedance. Therefore, in the case of the electrostatic type and the piezoelectric type, the circuit configuration becomes complicated and the inherent noise of the device also increases, so that it is desirable to use the electrodynamic type.

However, these two reasons show that it is preferable to use an electro-dynamic electroacoustic transducer in order to realize a contact microphone with ultra-high sensitivity. This does not indicate that an electrostatic or piezoelectric electroacoustic transducer cannot be used for the microphone. Of course, electrostatic and piezoelectric electro-acoustic transducers can be used in the same manner by taking the above problems into consideration.

[0054]

As described above, according to the present invention,
Since only the vibration of the object can be converted into electricity, even if the volume of the sound generated by the object is extremely small, it can withstand broadcast quality under normal circumstances without being affected by background noise.
/ N can be picked up.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a contact microphone using an electrodynamic electroacoustic transducer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the microphone unit in FIG. 1 in detail.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microphone unit 2 Base 3 Weight support pin 4 Object support plate 5 Anti-vibration spring (damper mechanism) 6 Feet (damper mechanism 7 Height adjusting screw (adjusting mechanism) 10 Contact pin 11 Electrodynamic electroacoustic transducer 111 Magnetic Body 112 Magnet 113 Coil 114 Spring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Morita 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Research Institute of Broadcasting (72) Inventor Atsushi Imai 1-10-11 Kinuta, Setagaya-ku, Tokyo No. Japan Broadcasting Corporation Broadcasting Research Institute F-term (reference) 5D021 DD03 5D125 DD05

Claims (6)

[Claims] 1. A contact-type microphone comprising: a needle-like contact pin whose tip contacts a vibrating object; and an electroacoustic transducer that converts vibration transmitted to the contact pin into an electric signal. 2. The contact microphone according to claim 1, further comprising: a damper mechanism configured to attenuate transmission of vibration of an installed environment to the contact pin. 3. The contact microphone according to claim 1, further comprising: an adjustment mechanism for integrally moving the contact pin and the electroacoustic transducer in the length direction of the contact pin. A contact microphone characterized by the following. 4. The contact microphone according to claim 1, further comprising: a support pin for supporting an object to be placed. 5. The contact microphone according to claim 1, wherein the electroacoustic transducer is movable with a magnetic circuit that generates a constant magnetic field and vibration of the contact pin. And a coil arranged in the constant magnetic field. 6. The contact type microphone according to claim 5, wherein the contact pin and the coil for electrically converting the vibration of the contact pin are supported by a thin film-shaped spring member. Contact microphone.