JP6432051B2 - Unidirectional dynamic microphone - Google Patents

Description

  The present invention relates to a unidirectional dynamic microphone.

  Among microphone devices, for example, handheld wireless microphones often use unidirectional dynamic microphone units as microphone units. The directivity of the dynamic microphone unit is defined by an acoustic resistance component for an omnidirectional component and an acoustic mass component for a bidirectional component. In the dynamic microphone, in order to adjust the omnidirectional component, an acoustic resistance and an air chamber are required at the rear part of the microphone unit (the back side of the diaphragm). If the rear air chamber is made smaller in order to reduce the size of the microphone device, the directional frequency response in the middle and low frequency band is deteriorated.

  In the handheld wireless microphone, a transmission unit for transmitting an audio signal to an acoustic device is necessary. For this reason, a small handheld wireless microphone is known in which a transmitter is provided integrally. However, when trying to reduce the size of a handheld wireless microphone with a built-in transmitter, the dimensions of the portion that accommodates the microphone unit that affects the performance (frequency characteristics, directivity, etc.) of the microphone are limited.

  Some microphone devices are provided with a shock mount that elastically supports the microphone unit with respect to the case in order to reduce an impact applied to the microphone unit. In the microphone device, when acceleration is applied from the side of the case, the microphone unit may swing around the portion supported by the shock mount. Further, when it is difficult to sufficiently secure the longitudinal dimension in the case due to downsizing of the microphone device, the microphone unit comes into contact with other components. If the microphone unit comes into contact with other parts, the diaphragm vibrates and an unpleasant impact sound is generated.

  As described above, in the microphone device, it is difficult to obtain high performance when the device is downsized.

  A technique is disclosed in which a microphone having a microphone unit mounted in a case via a shock mount is provided with stopper means for preventing the movement of the microphone unit (for example, see Patent Document 1).

  Even with the technique disclosed in Patent Document 1, it is difficult to obtain high performance when the microphone device is downsized.

JP-A-11-252675

  An object of the present invention is to provide a unidirectional dynamic microphone capable of obtaining high performance even when downsized.

The present invention
A microphone unit including a diaphragm that vibrates by sound, a magnet that generates a magnetic field in a magnetic gap, and a voice coil that is provided in the diaphragm and generates an electrical signal in the magnetic gap;
A support housing that forms an air chamber on the back side of the diaphragm;
A first support member for supporting the microphone unit on the support housing;
A second support member for supporting the microphone unit on the support housing at a position closer to the air chamber than the position of the first support member;
I have a,
The first support member supports the microphone unit in the vicinity of a hole that is provided on the back side of the diaphragm and allows sound from the back side of the diaphragm to pass toward the diaphragm.
The shape of the first support member defines the acoustic impedance of the sound intake passage including the hole,
It is characterized by that.

  According to the present invention, high performance can be obtained even when downsized.

It is sectional drawing which shows embodiment of the unidirectional dynamic microphone which concerns on this invention. It is sectional drawing which shows the modification of the shock mount of the dynamic microphone of FIG. It is an expanded sectional view of the microphone unit part of the dynamic microphone of FIG. FIG. 2 is an acoustic equivalent circuit diagram of the dynamic microphone of FIG. 1. It is sectional drawing which shows the dynamic microphone of a reference example.

  Hereinafter, embodiments of a unidirectional dynamic microphone, particularly a wireless dynamic microphone according to the present invention will be described with reference to the drawings.

  A dynamic microphone 1 with a built-in wireless function according to the embodiment of the present invention shown in FIG. 1 has a microphone unit 2 that converts sound into an electrical signal and outputs it, and a net 3 that surrounds the microphone unit 2. The directivity characteristic of the dynamic microphone 1 is defined by the balance of the combination of the omnidirectional component and the bidirectional component of the directivity characteristic. In order to realize unidirectionality in the dynamic microphone 1, it is necessary to optimize and design the acoustic impedance of each of the omnidirectional component and the bidirectional component. The dynamic microphone 1 obtains an omnidirectional component of directional characteristics by an acoustic resistance component. In addition, the dynamic microphone 1 obtains a directional characteristic bi-directional component from the acoustic mass component. The dynamic microphone 1 has an air chamber 4 at the rear of the microphone unit 2 in order to obtain an omnidirectional component. In the following description, the side where the microphone unit 2 is provided in FIG. 1 is the upper side, and the side where the air chamber 4 on the opposite side is provided is the lower side.

  The microphone unit 2 includes a diaphragm 21 that vibrates by sound and a magnetic circuit that is located below the diaphragm 21 and generates a magnetic field. The magnetic circuit includes a dish-shaped yoke 25, a disk-shaped magnet 22 attached to the upper surface of the yoke 25, and a disk-shaped pole piece 28 attached to the upper surface of the magnet 22. The microphone unit 2 includes a voice coil 23. The voice coil 23 is fixed to the back surface of the diaphragm 21 and generates an electrical signal with the magnet 22. The microphone unit 2 includes a unit case 24 that houses the diaphragm 21, the magnet 22, the voice coil 23, the yoke 25, the pole piece 28, and the like.

  The diaphragm 21 includes a center dome having a shape obtained by cutting a part of a spherical surface, and a sub dome having a partial arc shape in cross section and surrounding the periphery of the center dome. The diaphragm 21 is attached to the unit case 24 by fixing the outer peripheral edge of the sub dome to the unit case 24.

  The magnet 22 and the pole piece 28 constitute a magnetic circuit using a permanent magnet together with the yoke 25 in the unit case 24. The yoke 25 has an edge that rises upward so as to cover the outside of the voice coil 23. In the unit case 24, there is a cylindrical magnetic gap surrounded by the outer peripheral surface of the magnet 22 and the pole piece 28 and the inner peripheral surface of the yoke 25. A voice coil 23 fixed to the diaphragm 21 is disposed in the magnetic gap.

  The voice coil 23 is bonded along the boundary between the center dome and the sub dome. When receiving the sound wave, the diaphragm 21 vibrates in the vertical (vertical) direction corresponding to the sound wave together with the voice coil 23. The voice coil 35 that vibrates together with the diaphragm 21 generates power by crossing the magnetic flux in the magnetic gap and outputs an audio signal corresponding to the sound wave.

  The unit case 24 includes a front side unit case 241, a back side unit case 242, and a transformer housing case 243.

  The front unit case 241 covers the front side of the diaphragm 21. The front unit case 241 is provided with a hole 26 through which sound from the outside passes toward the front side of the diaphragm 21. On the front side of the hole 26, there is a front acoustic terminal that is the center position of air that moves simultaneously with the diaphragm 21.

  The back side unit case 242 covers the back side of the sub dome of the diaphragm 21. The rear unit case 242 is provided with a hole 27 through which sound from behind is passed toward the rear side of the diaphragm 21. In the vicinity of the hole 27, there is a rear acoustic terminal that is the center position of air that moves simultaneously with the diaphragm 21.

  The transformer accommodating case 243 accommodates a transformer 8 that boosts the output level of the audio signal. The transformer housing case 243 is provided below the back side unit case 242 and covers the back side of the center dome of the diaphragm 21. The transformer housing case 243 is provided with a wall-like connecting portion 245 that is connected to the back-side unit case 242 and a hole 246 that allows sound from the back side of the diaphragm 21 to pass through the diaphragm 21. The inside of the transformer housing case 243 constitutes a part of the air chamber 4.

  In the dynamic microphone 1, unidirectionality is obtained by optimizing the acoustic impedance of the omnidirectional component and the bidirectional component as described above. In the dynamic microphone 1, the front side of the diaphragm 21 in FIG.

  The dynamic microphone 1 has a shock mount 5. The shock mount 5 supports the microphone unit 2 on the support housing 7 in the vicinity of the center of gravity of the microphone unit 2 near the second acoustic terminal 27.

  The shock mount 5 corresponds to the first support member. The shock mount 5 is made of an elastic material such as various elastomers or rubber materials. The shock mount 5 includes a first connection portion 511, a second connection portion 521, and a wall surface portion 531. The shock mount 5 needs to have low stiffness in order to reduce vibration noise.

  The first connection portion 511 is connected to the first recess 244 of the unit case 24 located near the center of gravity of the microphone unit 2. The second connection portion 521 is connected to a second recess 71 provided on the upper end side of the support housing 7. The wall surface portion 531 is configured to connect the first connection portion 511 and the second connection portion 521, and is a wall surface that is convex with respect to the hole 27.

  In the dynamic microphone 1, when an external impact force is applied, the microphone unit 2 and the part from the microphone unit 2 to the transformer housing case 243 vibrate together. The shock mount 5 supports the unit case 24 in the vicinity of the center of gravity of the portion that vibrates as a unit. When receiving an impact from the outside, a rotational moment centered on the support position by the shock mount 5 is less likely to occur. For this reason, in the dynamic microphone 1, the movement of the microphone unit 2 is suppressed when an impact is applied from the outside, and the microphone unit 2 is difficult to rotate (swing motion) around the support portion of the shock mount 5.

  Thus, according to the dynamic microphone 1, since the microphone unit 1 does not contact other parts, unnecessary vibration of the diaphragm 21 due to contact is suppressed. Therefore, according to the dynamic microphone 1, generation of unpleasant impact sound due to the contact of the microphone unit 1 is prevented.

  In the dynamic microphone 1, the shock mount 5 supports the unit case 24 near the center of gravity of the microphone unit 2, and the shock mount 5 constitutes a part of the partition wall of the air chamber 4. For this reason, the volume of the air chamber 4 can be sufficiently secured to reduce the size of the apparatus. In other words, the volume of the air chamber 4 is not sacrificed when the microphone device is downsized.

  The shock mount 5 defines a part of acoustic mass (mass component of acoustic impedance) near the hole 27 by the shape of the wall surface portion 531. The shape of the wall surface portion 531 is a substantially arc-shaped curved surface protruding toward the opening of the hole 27. For this reason, by changing the shape of the wall surface portion 531 of the shock mount 5, it is possible to change the acoustic impedance for the sound entering from the hole 27. The shape of the wall surface portion 531 of the shock mount 5 is not limited to the shape described above. For example, as shown in FIG. 2, the shape of the wall surface portion 531 </ b> A of the shock mount 5 </ b> A may be a substantially arcuate curved surface that is recessed with respect to the hole 27.

  The dynamic microphone 1 has a gasket 6. With the gasket 6, the microphone unit 2 is supported by the support housing 7 in the air chamber 4 at a position behind the support position by the shock mount 5 in the direction of the directional axis (near the air chamber 4 in FIG. 1).

  The gasket 6 corresponds to the second support member. The gasket 6 supports the microphone unit 2 on the support housing 7 by contacting the outer wall surface of the transformer housing case 243 and the inner wall surface of the support housing 7. The gasket 6 is formed of a low-resilience closed cell sponge or a flexible urethane foam having both elasticity and viscosity (having viscoelasticity). For example, when a flexible urethane foam is used for the gasket 6, the elasticity of the flexible urethane foam is kept low and the viscosity is increased. Therefore, the gasket 6 has a low rebound resilience with a large hysteresis loss rate.

  The gasket 6 is a material having air permeability. In the dynamic microphone 1, the gasket 6 is interposed at a position that partitions the space inside the wall surface portion 531 of the shock mount 5 and the air chamber 4. Since the gasket 6 is a material having air permeability, the gasket 6 does not substantially limit the volume of the air chamber 4. For this reason, in the dynamic microphone 1, the part from the partition wall 72 to the shock mount 5 can also function as the air chamber 4.

  The gasket 6 also prevents the shock mount 5 from vibrating by sound waves and propagating the sound waves to the air chamber. The shock mount 5 is designed to be thin so as to reduce stiffness in order to reduce vibration noise. Such a shock mount 5 may vibrate by sound waves and propagate the sound waves to the air chamber 4. Sound waves mixed into the air chamber via the shock mount 5 are absorbed by the gasket 6. Therefore, the gasket 6 prevents the sound wave mixed through the shock mount 5 from propagating to the rear side of the diaphragm 22.

  In the dynamic microphone 1, the viscoelastic gasket 6 supports the unit case 24, so that the movement of the unit case 24 due to impact and pressure fluctuations in the air chamber 4 can be suppressed. For this reason, in the dynamic microphone 1, the microphone unit 1 does not come into contact with other components and vibrate unnecessary for the diaphragm 21. Therefore, such a dynamic microphone 1 can prevent generation of unpleasant impact sound.

  Further, the gasket 6 has an elastic modulus lower than the elastic modulus of the shock mount 5, specifically, a stiffness about 1/5 of the stiffness of the shock mount 5. That is, the stiffness of the shock mount 5 is dominant between the shock mount 5 and the gasket 6. For this reason, the gasket 6 converges an impact that cannot be converged only by the shock mount 5 when receiving an impact from the outside.

  The support housing 7 is connected to a body for holding the dynamic microphone 1 by a speaker's hand. The support housing 7 forms the air chamber 4 together with the wall surface portion 531 of the shock mount 5, the partition wall 72, and the transformer housing case 243. That is, the air chamber 4 is a portion defined by the inner wall of the support housing 7, the wall surface portion 531, the partition wall 72, and the transformer housing case 243.

  As shown in FIG. 3, in the example of the dynamic microphone 1, the acoustic resistance material 9 is provided in a space that constitutes a part of the air chamber 4 formed by the back-side unit case 242 and the transformer housing case 243. . The acoustic resistance material 9 makes it possible to adjust the acoustic impedance on the back side of the diaphragm 21. In FIG. 3, the acoustic resistance material 9 is shown so as to fill the space formed by the back unit case 242 and the transformer housing case 243, but is partially disposed near the back side of the hole 246 and the diaphragm 21. It may be.

FIG. 4 shows an acoustic equivalent circuit diagram of the dynamic microphone 1. The acoustic equivalent circuit is denoted by the same reference numerals as in FIG. An audio signal _{P 1} from the hole 26, the vibration plate 21 having an acoustic stiffness _{m 0} and acoustic mass _{s 0} by the audio signal _{P 2} passing through the holes 27 having an acoustic stiffness _{m 1} and the acoustic resistance _{r 2} vibrates. At this time, if a pressure fluctuation occurs in the air chamber 4, a change occurs in the acoustic mass s ₁ , and vibration is transmitted to the diaphragm 21, resulting in noise. According to the dynamic microphone 1, since the gasket 6 also suppresses the movement of the shock mount 5, vibration noise due to pressure fluctuations in the air chamber 4 can be suppressed.

  FIG. 5 is a cross-sectional view showing a conventional dynamic microphone 10 as a reference example. In the dynamic microphone 10 of the reference example, the vertical dimension of the transformer 80 is different, and the portion supported by the support housing 70 is larger in the vertical direction than the dynamic microphone 1. Moreover, in the dynamic microphone 10 of the reference example, the microphone unit 2 is supported by the first shock mount 51 and the second shock mount 52 that are made of a material having the same elastic modulus.

  With the above configuration, the volume of the air chamber 40 cannot be increased in the dynamic microphone 10 of the reference example. In the dynamic microphone 10 of the reference example, there is no difference in stiffness between the first shock mount 51 and the second shock mount 52. For this reason, in the dynamic microphone 10 of the reference example, the microphone unit 2 rotates or vibration noise occurs when an external impact or a pressure fluctuation of the air chamber 4 occurs.

  On the other hand, according to the dynamic microphone 1 according to the present embodiment described above, the following effects can be obtained.

  According to the dynamic microphone 1, it is possible to suppress displacement of the microphone unit 2 and vibration noise due to pressure fluctuations and impacts in the air chamber. Moreover, according to the dynamic microphone 1, since the volume of the air chamber 4 can be ensured, the design which considered the favorable directional frequency response in a mid-low frequency band is attained. In addition, according to the dynamic microphone 1, even if components (circuit board, battery, etc.) other than the microphone unit are built in, the shock mount 5 and the gasket 6 reduce the displacement (rotational motion) due to imbalance in weight balance. Therefore, it is possible to prevent deterioration of acoustic balance and vibration noise due to positional deviation.

  For this reason, according to the dynamic microphone 1, high performance can be obtained even when it is downsized.

  According to the dynamic microphone 1, even a microphone in which components such as a transmission unit other than the microphone unit are mounted, such as a handheld wireless microphone, can obtain high performance when downsized.

DESCRIPTION OF SYMBOLS 1 Dynamic microphone 2 Microphone unit 3 Net 4 Air chamber 5 Shock mount 6 Gasket 7 Support housing 8 Transformer 9 Acoustic resistance material 21 Diaphragm 22 Magnet 23 Voice coil 24 Unit case 25 Yoke 26 Hole 27 Hole 28 Pole piece 71 2nd recessed part 72 Partition 241 Front side unit case 242 Rear side unit case 243 Transformer housing case 244 First recess 245 Connection portion 246 Hole 511 First connection portion 521 Second connection portion 531 Wall surface portion

Claims (8)

A microphone unit including a diaphragm that vibrates by sound, a magnet that generates a magnetic field in a magnetic gap, and a voice coil that is provided in the diaphragm and generates an electrical signal in the magnetic gap;
A support housing that forms an air chamber on the back side of the diaphragm;
A first support member for supporting the microphone unit on the support housing;
A second support member for supporting the microphone unit on the support housing at a position closer to the air chamber than the position of the first support member;
I have a,
The first support member supports the microphone unit in the vicinity of a hole that is provided on the back side of the diaphragm and allows sound from the back side of the diaphragm to pass toward the diaphragm.
The shape of the first support member defines the acoustic impedance of the sound intake passage including the hole,
Unidirectional dynamic microphone. The first support member and the second support member are formed of an elastic material.
The unidirectional dynamic microphone according to claim 1. The second support member has an elastic modulus lower than that of the first support member.
The unidirectional dynamic microphone according to claim 2. The first support member supports the microphone unit in the vicinity of the center of gravity of the microphone unit;
The unidirectional dynamic microphone according to any one of claims 1 to 3. The second support member supports the microphone unit inside the air chamber.
The unidirectional dynamic microphone according to any one of claims 1 to 4. The first support member is a shock mount;
The unidirectional dynamic microphone according to any one of claims 1 to 5. The material of the second support member is a material having air permeability.
The unidirectional dynamic microphone according to any one of claims 1 to 6. The first support member forms a part of the air chamber together with the support housing.
The unidirectional dynamic microphone according to any one of claims 1 to 7.

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