JP4737546B2 - Method for manufacturing variable directional condenser microphone unit and variable directional condenser microphone - Google Patents

Description

  The present invention relates to a method of manufacturing a variable directivity condenser microphone unit and a variable directivity condenser microphone, and in particular, in which each pair of diaphragms functions as an acoustic resistance material by having a pressure equivalent opening, This is focused on ensuring the consistency of the acoustic resistance value of the diaphragm.

  Generally speaking, the variable directional condenser microphone unit is composed of a diaphragm, a fixed electrode disposed opposite to the diaphragm with a gap therebetween, and a rear sound disposed opposite to the fixed electrode. A microphone element provided with a resistance material as a main component has a structure in which two microphone elements are joined together in a back-to-back manner. As the diaphragm, for example, a synthetic resin film made of polyphenylene sulfide (PPS) having a thickness of 2 μm is used as a base, and a conductive metal film such as gold is deposited thereon.

  The variable directivity condenser microphone unit has a pair of condenser microphone elements connected back and forth in the back-and-forth manner as described above.Therefore, there are acoustic terminals on the front and rear elements, and the diaphragm functions as the acoustic terminal. Plays. When the degree of sealing between the elements is high due to the combination of the pair of microphone elements, an atmospheric pressure difference is generated between the inside and outside of the element as the atmospheric pressure varies, and the diaphragm is displaced by this atmospheric pressure difference. When the atmospheric pressure is lowered, the diaphragm may bulge outward like a balloon, and the diaphragm may be destroyed. When the atmospheric pressure increases, the diaphragm is pushed inward, and the diaphragm may come into contact with the fixed electrode. For this reason, the variable directivity condenser microphone unit employs a configuration in which air is circulated by bypassing the inside and outside of the unit to eliminate the pressure difference between the inside and outside of the unit. Eliminating this pressure difference is called pressure equivalence.

  If the structure of the variable directional condenser microphone unit is roughly divided, the two microphone elements can be separated into the front and back, that is, the structure in which a pair of condenser microphone elements are combined back and forth as described above. In addition, there is a non-separable structure in which two microphone elements including a diaphragm and a fixed electrode are incorporated in one unit case. The variable directional condenser microphone unit having a separated structure has two microphone elements connected by a ring-shaped coupler with a gasket interposed therebetween. Therefore, when connecting two microphone elements, pressure equivalence can be easily realized by giving a high acoustic resistance to the gasket. Giving a gasket high acoustic resistance means that air is circulated inside and outside to a degree that can sufficiently cope with fluctuations in atmospheric pressure, although air circulation is limited.

  In order to reduce manufacturing costs, the variable directional condenser microphone unit with a non-separable structure includes a pair of microphone element components that are assembled in a sealed state around a single base, and omits gaskets and couplers. It has a possible structure. For this reason, if there is no kind of air flow opening in the pair of diaphragms, pressure equalization inside and outside cannot be performed, so the pressure equivalent openings are formed in the diaphragm.

  In order to provide a pressure equivalent opening in the diaphragm, the present applicant has proposed a method of applying heat by spark discharge to a predetermined portion of the diaphragm (see, for example, Patent Document 1). According to this method, since no burr is generated at the periphery of the opening, it is possible to prevent generation of noise due to contact of the conductive metal film of the diaphragm with the fixed electrode, and variation in the diameter of the opening is relatively small. There are advantages that can be done.

  However, even if a method for providing a pressure equivalent opening in the diaphragm by applying heat from spark discharge is used, there is variation in air leakage (circulation) resistance, which is a factor in the bidirectionality of the microphone unit. The problem that the frequency response of the low frequency varies between the front side and the rear side is unresolved. In the bidirectionality of the microphone unit, in order to eliminate the variation in the low-frequency response between the front side and the rear side, it is necessary to incorporate diaphragms with equal air leakage resistance into the front and rear microphone elements. For this purpose, it is necessary to measure the air leakage resistance, that is, the degree of air leakage. Here, the air leakage resistance can be referred to as acoustic resistance from an acoustic aspect, and measuring the air leakage resistance of the diaphragm also measures the acoustic resistance of the diaphragm.

The present applicant has previously applied for a patent regarding an acoustic resistance measuring device and an acoustic resistance adjusting method (see Patent Document 2). The invention described in Patent Document 2 includes a first pipe in which one end is connected to a compressed air supply source and a reference acoustic resistance material is arranged at the other end, and one end is connected to the compressed air supply source and the other end is an acoustic resistance to be measured. A second pipe in which the material is disposed, an air throttle part provided in the middle of each of the first pipe and the second pipe, and the first pipe and the second pipe connected downstream of the air throttle part in the air flow direction. And a differential pressure gauge that is provided in the bridge pipe and measures a pressure difference between the first pipe and the second pipe.
The invention described in Patent Document 2 can be applied to the acoustic resistance measurement of the diaphragm in the present invention. However, although invention of patent document 2 assumes using a compressed air supply source, what is necessary is just to be able to generate an air flow in the 1st piping and the 2nd piping, A weak vacuum generating means for sucking air to make the inside of the pipe have a negative pressure can be used as an air flow generation source as well as a compressed air supply source.

JP-A-9-84195 JP 2005-328347 A

The present invention makes it possible to reliably and stably obtain bi-directional characteristics having the front and rear low-frequency response characteristics while utilizing the above-described conventional technology, so that a high-performance variable directivity condenser microphone can be obtained at low cost. It is an object of the present invention to provide a method for manufacturing a variable directivity condenser microphone unit that can be obtained.
Another object of the present invention is to provide a high-performance variable directivity condenser microphone at low cost by using the microphone unit manufactured by the above method.

The manufacturing method of the variable directivity microphone unit according to the present invention includes two air flow paths whose one ends are collectively connected to an air flow generation source, and the tips of the two air flow paths are respectively connected to a differential pressure gauge. The acoustic resistance measuring device should be used, the diaphragm should be set at the tip of one air flow path of the acoustic resistance measuring device, the reference acoustic resistance material should be set at the tip of the other air flow path, and the diaphragm should be set One end of the air flow path is a funnel-shaped receiving part, the diaphragm is fixed to the diaphragm holder at the outer periphery, and the diaphragm integrated with the diaphragm holder is the funnel-shaped receiving part. The air flow generation source sucks the air in the air flow path, measures the acoustic resistance of each diaphragm based on the pressure difference in the two air flow paths, and determines the appropriate acoustic resistance. microphone and the diaphragm value pairs The most important feature be incorporated into the unit.

  The variable directional condenser microphone according to the present invention is obtained by incorporating a variable directional condenser microphone unit manufactured by the method according to the present invention into a microphone case as a variable directional condenser microphone unit.

  According to the manufacturing method of the variable directivity condenser microphone unit according to the present invention, the acoustic resistance is measured for each pair of diaphragms, and the diaphragm having an appropriate acoustic resistance value is incorporated into the microphone unit. The sound resistance value can be made uniform, and bi-directionality with the front and rear low-frequency response characteristics can be obtained reliably and stably, so that a high-performance variable-directional condenser microphone can be obtained at low cost. .

Using an acoustic resistance measuring device with two air flow paths connected at one end to the air flow source in a lump, using a diaphragm at the tip of one air flow path and a reference acoustic resistance at the tip of the other diaphragm By setting the material and measuring the acoustic resistance of the diaphragm based on the pressure difference between the two air flow paths, the acoustic resistance of the diaphragm can be measured easily and accurately.
When the air flow generation source of the acoustic resistance measuring device is one that sucks air in the air flow path, the diaphragm having the outer peripheral edge fixed to the diaphragm holder is received by the funnel-shaped receiver of one air flow path. The diaphragm is adsorbed to the receiving part only by being placed on the part, and a special kind of pressing member is not required. Therefore, the configuration of the measuring device is simplified and the measurement is facilitated.

  According to the variable directivity condenser microphone according to the present invention, since the variable directivity condenser microphone unit manufactured by the method according to the present invention is used, the acoustic resistance values of the paired diaphragms can be made uniform, and the front and rear are reduced. Bidirectionality with uniform frequency response characteristics can be obtained reliably and stably, so that a high performance variable directivity condenser microphone can be obtained at low cost.

Hereinafter, a method for manufacturing a variable directivity condenser microphone unit and an embodiment of a variable directivity condenser microphone according to the present invention will be described with reference to the drawings.
First, an embodiment of a variable directivity condenser microphone according to the present invention will be schematically described. In FIG. 8, the variable directional condenser microphone 10 is configured by incorporating a variable directional condenser microphone unit 18 in a microphone case 12. The variable directional condenser microphone unit 18 is a variable directional condenser microphone unit manufactured by a method according to one of the embodiments of the present invention described later. A front mesh 14 is coupled to the upper end of the microphone case 12, and a portion corresponding to the microphone unit 18 is covered with the front mesh 14. A microphone connector 16 is provided at the rear end (lower end) of the microphone case 12. A cable connector can be coupled to the microphone connector 16 to guide the output signal of the microphone to the outside.

The variable directivity condenser microphone unit 18 converts the sound from the front side and the back side into an electrical signal by integrally forming two microphone elements in a back-to-back manner, and a characteristic curve representing directivity is provided in the front-rear direction. Has bi-directionality to draw figure 8. And directivity can be changed by changing the voltage applied between the diaphragm which comprises a capacitor | condenser, and the fixed electrode facing this, and its polarity.
Next, an embodiment of a method for manufacturing a variable directivity condenser microphone unit will be described.

  The embodiment shown in FIGS. 1 and 2 shows an example of a variable directional condenser microphone unit in which two individually configured condenser microphone elements 21 and 41 are coupled back to back. In FIGS. 1 and 2, reference numeral 22 denotes a diaphragm-like diaphragm, and the diaphragm 22 has a peripheral edge fixed to the outer peripheral edge of the diaphragm holder 23. The diaphragm holder 23 is in the shape of a circular flat dish, and the outer peripheral edge of the diaphragm 22 is fixed to a flat surface formed on the outer peripheral edge, and from the surface corresponding to the bottom surface of the diaphragm holder 23. They are separated by a predetermined interval. The diaphragm 22 is mounted on the disk-like fixed electrode 26 through a very thin ring spacer in a form held integrally with the diaphragm holder 23, and the diaphragm 22 and the upper surface of the fixed electrode 26 are connected to each other. They face each other with a minute gap corresponding to the thickness of the spacer. The spacer is interposed between the diaphragm 22 and the fixed electrode 26 near the outer periphery thereof.

  The lower surface of the outer peripheral portion of the fixed electrode 26 is placed on the upper surface of the outer peripheral portion of the circular cover 27. A portion other than the outer peripheral portion is scraped off on the upper surface of the cover 27 to form a recessed portion, and the bottom surface of the recessed portion of the cover 27 and the lower surface of the fixed electrode 26 are opposed to each other with an appropriate interval. A male screw is formed on the outer peripheral surface of the cover 27, and a female screw formed on the inner periphery of the presser ring 30 is screwed into the male screw. The presser ring 30 has an inward flange on the side opposite to the screwed portion with the cover 27, and the inward flange presses the outer surface of the outer peripheral edge of the diaphragm holder 23, so that the cover 27 and the fixed electrode 26 are pressed. The spacer, the diaphragm 22, and the diaphragm holder 23 are integrally coupled to constitute one microphone element 21.

  A plurality of holes 24 are formed in the diaphragm holder 23, and these holes 24 serve as front acoustic terminals of the microphone element 21. A hole 28 is formed in the center of the cover 27, and the hole 28 serves as a rear acoustic terminal for the microphone element 21. The hole 28 is covered with an acoustic resistance material 29. In the center portion of the fixed electrode 26, a hole is formed to communicate the gap between the diaphragm 22 and the fixed electrode 26 with the hole 28 of the cover 27 serving as the rear acoustic terminal. A voltage is applied between the fixed electrode 26 and the diaphragm 22 from the outside. An electrode 25 extends outward from the center of the diaphragm holder 23 in the direction perpendicular to the surface of the diaphragm holder 23, and the electrode 25 is electrically connected to the diaphragm 22 via the diaphragm holder 23. Connected. The electrode 25 is formed of a screw. The screw is inserted from the inner surface side of the diaphragm holding body 23, and a nut is screwed to the screw from the outer surface side of the diaphragm holding body 23 to be tightened. It is fixed to the holding body 23.

  Another microphone element 41 coupled back to back to the one microphone element 21 described above is also configured in the same manner as the microphone element 21. Reference numeral 42 is a diaphragm, 43 is a diaphragm holder, 44 is a hole constituting a front acoustic terminal, 45 is an electrode, 46 is a fixed electrode, 47 is a cover, 48 is a hole constituting a rear acoustic terminal, 49 is an acoustic Resistive material 50 and a presser ring are shown. The members that match the names of the members constituting the microphone element 21 are configured in the same manner as the members in the microphone element 21.

  One microphone element 21 and another microphone element 41 are coupled back to back, but are coupled with a gasket 51 between the microphone elements 21 and 41. Further, as coupling means for the microphone elements 21 and 41, the above-described female screw of the coupler 52 having an internal thread formed on the inner peripheral surface thereof, the cover 27 on the one microphone element 21 side, and the outer peripheral surface of the cover 47 of the other microphone element 41 are provided. Each male screw formed is screwed. The covers 27 and 47 are coupled to each other while compressing the gasket 51 by screwing the covers 27 and 47 from both sides of the coupler 52.

  When the pair of microphone elements 21 and 41 are coupled in an airtight state, the rear acoustic terminals of the microphone elements 21 and 41 are sealed, and the diaphragms 22 and 42 bulge outward or are fixed due to a change in external air pressure. It contacts the electrodes 26 and 46. Therefore, the gasket 51 interposed between the microphone elements 21 and 41 is provided with air permeability so that the internal space communicates with the outside air to enable pressure equivalence. Since the change in pressure of the outside air is gradual, a slight air permeability is provided, and the sound wave is configured not to pass as much as possible.

  As described above, pressure equivalence is performed by providing the gasket 51 with air permeability. However, as described in Patent Document 1, pressure equivalence is performed by providing openings in the diaphragms 22 and 42. Also good. The method of providing the pressure equalization openings in the diaphragms 22 and 42 is arbitrary, and a method of forming the openings by heat by spark discharge as described in Patent Document 1 may be used. By providing the pressure equalization openings in the diaphragms 22 and 42, the acoustic resistance of the diaphragms 22 and 42 changes, and the conditions such as the size and position of the openings change to change the acoustic characteristics of the diaphragms 22 and 42. The resistance value changes. It is desirable that the acoustic resistance values of the pair of diaphragms 22 and 42 are substantially the same. Therefore, the respective acoustic resistance values are measured before the diaphragms 22 and 42 are assembled, and diaphragms having substantially the same acoustic resistance value are selected as a pair and assembled as a microphone unit. A method for measuring the acoustic resistance value is arbitrary, but a preferable measuring method will be described later.

  According to the embodiment described above, the acoustic resistance is measured for each of the paired diaphragms 22 and 42, and the diaphragm of the appropriate acoustic resistance value is incorporated into the microphone unit. The resistance values can be made uniform, and the bi-directionality having the front and rear low-frequency response characteristics can be obtained reliably and stably, so that a high-performance variable-directional condenser microphone can be obtained at a low cost.

  The microphone element 21 and the microphone element 41 each function as an independent electroacoustic transducer, and the sound wave entrance from the rear acoustic terminal side is substantially blocked, so that the sound wave from the front of each is This is sensed and converted into an electric signal to constitute a bidirectional microphone unit. In each microphone element 21 and microphone element 41, when the voltage applied between the diaphragm and the fixed electrode is individually changed, the directivity of the microphone element is changed individually, and the directivity of the entire microphone unit is changed. By switching the polarity of the voltage applied to both elements, it is possible to switch to a non-directional microphone unit, a bidirectional microphone unit, or the like.

  Next, a second embodiment shown in FIGS. 3 and 4 will be described. This embodiment is an embodiment of a variable directivity condenser microphone unit that is relatively simple in structure and inexpensive, in which a pair of microphone elements 70 and 80 are incorporated on both sides of a base 60. 3 and 4, an acoustic terminal hole 61 serving as a rear acoustic terminal of the pair of microphone elements 70 and 80 is formed at the center of the short columnar base 60. In the acoustic terminal hole 61, a pair of acoustic resistance members 78 and 88 are attached at a predetermined interval so as to close the acoustic terminal hole 61. The acoustic resistance material 78 is an acoustic resistance material on the microphone element 70 side, and the acoustic resistance material 88 is an acoustic resistance material on the microphone element 80 side. On both end faces of the base 60, recesses 63, 64 are formed by cutting along a circle centered on the central axis of the base 60. Further, the recesses 63, 64 are slightly smaller in diameter than the recesses 63, 64. Concave portions 65 and 66 are formed.

  A fixed electrode 76 is fitted in the recessed portion 63 of the base 60. The thickness dimension of the fixed electrode 76 is larger than the depth dimension of the recessed portion 63, and a part of the fixed electrode 76 protrudes from the end surface of the base 60. On the fixed electrode 76, a thin ring-shaped spacer 73, a diaphragm 71 having an outer peripheral edge fixed to a ring-shaped diaphragm holder 72, and a ring-shaped electrode plate 74 are stacked in this order, A cover 77 having a cylindrical shape and having an inward flange at one end is covered. The cylindrical portion of the cover 77 covers the outer periphery of the electrode plate 74, the diaphragm holding body 72, the diaphragm 71, and the spacer 73. The cover 77 is fitted on the outer periphery of one end of the base 60 and is integrally coupled to the base 60. The coupling means between the base 60 and the cover 77 is arbitrary, and may be press-fitted or may be screwed. When the cover 77 is coupled to the base 60, the electrode plate 74 is pressed by the inward flange portion of the cover 77, and the diaphragm holder 72, the diaphragm 71, the spacer 73, and the fixed electrode 76 are pressed in the following order. These are fixed to the base 60.

  A minute gap corresponding to the thickness of the spacer 73 is formed between the vibration plate 71 and the fixed electrode 76, and the vibration plate 71 and the fixed electrode 76 face each other with this gap, and the vibration plate 71 and the fixed electrode 76 are fixed. The electrode 76 constitutes a capacitor. The spacer 73 is made of an insulator. The diaphragm holder 72 and the electrode plate 74 are made of a conductor, and a voltage is applied to the diaphragm 71 from the outside through a terminal portion 75 rising outward from the inner peripheral portion of the electrode plate 74. ing.

  The other microphone element 80 is configured similarly to the microphone element 70. Reference numeral 81 is a diaphragm, 82 is a diaphragm holder, 83 is a spacer, 86 is a fixed electrode, 84 is an electrode plate, 87 is a cover, and 64 is a concave portion of the base 60 into which the fixed electrode 86 is fitted. . The members that coincide with the names of the members constituting the microphone element 70 are configured in the same manner as the members in the microphone element 70. The acoustic terminal hole 61 of the base 60 constitutes a rear acoustic terminal common to the microphone elements 70 and 80. The acoustic resistance material 78 is a rear acoustic resistance material of the microphone element 70, and the acoustic resistance material 88 is a rear acoustic resistance material of the microphone element 80. Although not shown, holes are formed in both the fixed electrodes 76 and 86 so that the gap between the diaphragms 71 and 81 and the fixed electrodes 76 and 86 communicates with the rear acoustic terminal hole 61.

  According to the embodiment shown in FIGS. 3 and 4, the inner space defined by both diaphragms 71 and 81 is sealed, thereby providing bidirectionality. However, if the space is completely sealed, the diaphragms 71 and 81 have the above-described problems. Therefore, as described in Patent Document 1, a pressure equivalent opening is formed in the diaphragm. Is provided. The pressure equivalent opening is provided near the outer periphery of the diaphragm close to the holding portion by the diaphragm holder so as not to affect the acoustic characteristics as much as possible. The diameter of the pressure equivalent opening is in the range of 50 μm to 0.1 mm. Although it is desirable that the acoustic resistance values of the diaphragms 71 and 81 in both microphone elements 70 and 80 are substantially the same, the acoustic resistance value varies depending on variations in the diameter of the pressure equivalent opening and other conditions. Therefore, it is difficult to select and combine the diaphragms 71 and 81 having substantially the same acoustic resistance value based on only the appearance.

  Therefore, the acoustic resistance value of the diaphragm is measured using a measuring device as described in Patent Document 2, and a diaphragm having substantially the same acoustic resistance value is selected from the measurement results and incorporated in the microphone unit. I did it. Hereinafter, an example of an acoustic resistance value measuring apparatus will be described.

  In FIG. 5, reference numerals 91 and 92 denote air flow paths. One end (the lower end in the figure) of the two air flow paths 91 and 92 is collectively connected to the air flow generation source by the communication path 102. The air flow generation source may be a compressed air generation device, or an air suction device that creates a weak vacuum (negative pressure) in the air flow paths 91 and 92. In this embodiment, the air flow generation source is an air suction device. In the middle of the two air flow paths 91 and 92, air flow rate adjusting devices 94 and 95 such as needles are provided, and a reference air resistance is set by the adjusting devices 94 and 95.

  The front end of one air flow path 91 is a receiving portion 96 opened in a funnel shape, and the open upper end edge of the receiving portion 96 is a flat portion 97. In the case of the embodiment shown in FIG. 3 and FIG. 4, a vibration plate that is held by a vibration plate holder and that has an opening for pressure equivalence is placed on the flat portion 97 together with the vibration plate holder. FIG. 5 shows an example in which the diaphragm 71 held by the diaphragm holder 72 is placed. A reference air resistance 98 including an air flow rate adjusting device such as a needle is provided at the tip of the other air flow path 92. The two air flow paths 91 and 92 are connected to the differential pressure gauge 100 at the lower part of the receiving part 96 and the lower part of the reference air resistance 98, and the differential pressure gauge 100 reads the difference in air pressure between the two air flow paths 91 and 92. By comparing with the reference air resistance 98, the air resistance value of the diaphragm 71 can be obtained. Then, the acoustic resistance value of the diaphragm 71 can be obtained from the air resistance value.

  While exchanging the diaphragm integrated with the diaphragm holder placed on the receiving portion 96 of the measuring apparatus, the acoustic resistance value is obtained for each diaphragm as described above. From the obtained acoustic resistance values, diaphragms having substantially the same acoustic resistance value are selected and incorporated in one microphone unit. As a result, it is possible to configure a variable directivity condenser microphone unit that is excellent in bidirectionality and thus can change the directivity as intended.

  By using an air suction device as the air flow generation source, there is an advantage that the diaphragm to be measured can be easily set on the receiving portion 96. That is, since the air flow generation source is an air suction device, the air flow paths 91 and 92 are in a negative pressure or a weak vacuum, and the diaphragm is mounted on the receiving portion 96 by simply placing the vibrating plate on the receiving portion 96. This is because the integral diaphragm is attracted and its outer peripheral edge is adsorbed by the flat portion 97. In this state, external air is sucked into the air flow path 91 through the pressure equivalent opening provided in the diaphragm. If the pressure equalization opening is small and the air flow rate in the air flow path 91 is small, the air pressure in the air flow path 91 is low. Reading the display on the differential pressure gauge 100 increases the air resistance of the diaphragm, and the acoustic resistance value is also high. I understand that it is expensive. Incidentally, the acoustic resistance value of the diaphragm can be measured even when the air flow generation source is used as the compressed air supply source. In this case, it is necessary to provide a diaphragm pressing mechanism so that the diaphragm does not float from the flat surface 97 of the receiving portion 96.

  FIG. 6 shows a more specific example of the acoustic resistance measurement device shown in FIG. The same components as those of the measurement apparatus shown in FIG. In the measuring apparatus shown in FIG. 6, the main body includes a block, air flow paths 91 and 92 are formed in the block, and the lower ends of the air flow paths 91 and 92 communicate with the communication path 102. A central portion in the length direction of the connecting path 102 is connected to an air flow generation source via a connector 101, and openings of the connecting path 102 at both ends of the block are closed by bolts 104 and 105. Needles as adjusting devices 94 and 95 are provided in the middle of the air flow paths 91 and 92. Connectors 108 and 109 are provided at the upper ends of the air flow paths 91 and 92, respectively. The receiving part 96 shown in FIG. 5 is connected to the connector 108 on the air flow path 91 side, and the connector 109 on the air flow path 92 side is connected to the connector 109. A reference air resistance 98 shown in FIG. 5 is connected. A pipe is connected between the adjusting device 94 of the air flow channel 91 and the connector 108 and between the adjusting device 95 of the air flow channel 92 and the connector 109 via connectors 106 and 107, respectively. A differential pressure gauge as indicated by reference numeral 100 is arranged. The measurement apparatus shown in FIG. 6 is substantially the same as the measurement apparatus shown in FIG. 5, and the acoustic resistance of the diaphragm can be measured by the same operation.

  The diaphragm that can be measured by the measuring apparatus shown in FIGS. 5 and 6 is not limited to the diaphragm in the embodiment shown in FIGS. 3 and 4, but the acoustic resistance of the diaphragm in the embodiment shown in FIGS. Can also be measured. In this case as well, measurement is performed by setting the diaphragm on the receiving portion of the measuring apparatus while being held by the diaphragm holder.

  As described above, by making the acoustic resistance values of the pair of diaphragms constituting the variable directivity condenser microphone unit the same, the front and rear bi-directional characteristics are aligned, and the bi-directional characteristics are symmetric. FIG. 7 shows this effect by actual measurement, (a) is an arbitrary combination without measuring the acoustic resistance value of the diaphragm for comparison, and (b) is the acoustic resistance value of the front and rear diaphragms. Shows the directional characteristics of the lineup. The horizontal axis is the frequency of the input audio, the vertical axis is the output level, and the unit is dBV. 0 °, 180 °, 90 °, and 270 ° are angles with respect to the reference direction in the front-rear direction. When 0 ° is the front, the back is 180 °. As is apparent from a comparison between FIG. 7A and FIG. 7B, according to the embodiment of the present invention, the directivity in the front-rear direction of 0 ° and 180 ° is well aligned, and 90 ° and 270. The horizontal directionality of ° is well aligned. Therefore, when changing the voltage applied to the front and rear microphone elements or switching the polarity of the voltage to change the directivity, it is easy to set the intended directivity.

  The variable directivity condenser microphone unit manufactured by the method described above can be obtained by incorporating this into a microphone case to obtain a variable directivity condenser microphone as shown in FIG. As a result, the diaphragms of the microphone elements paired in the front and rear have substantially the same acoustic resistance value, and a variable directivity condenser microphone in which the directivity of the front and rear microphone elements is well aligned can be obtained.

It is a longitudinal cross-sectional view which shows the 1st example of the variable directivity condenser microphone unit which can apply the manufacturing method concerning this invention. It is a longitudinal cross-sectional view which decomposes | disassembles and shows the 1st example of the said variable directivity condenser microphone unit. It is a longitudinal cross-sectional view which shows the 2nd example of the variable directivity condenser microphone which can apply the manufacturing method concerning this invention. It is a longitudinal cross-sectional view which decomposes | disassembles and shows the 2nd example of the said variable directivity condenser microphone unit. It is the schematic which shows the example of the acoustic resistance measuring apparatus which can be used for the manufacturing method of this invention. It is a longitudinal cross-sectional view which shows the example which actualized the said acoustic resistance measuring apparatus more. This shows the directivity of the variable directivity condenser microphone unit. (A) is a characteristic diagram when the acoustic resistances of the pair of vibrating bodies are not aligned, and (b) is a characteristic diagram when the acoustic resistances of the pair of vibrating bodies are aligned. is there. It is a front view which shows the example of the variable directivity condenser microphone provided with the microphone unit manufactured by the method concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Condenser microphone element 22 Diaphragm 23 Diaphragm holder 24 Acoustic terminal hole 25 Electrode 26 Fixed electrode 27 Front cover 28 Acoustic terminal hole 29 Acoustic resistance material 41 Condenser microphone element 42 Diaphragm 43 Diaphragm holder 44 Acoustic terminal hole 45 Electrode 46 Fixed electrode 47 Full cover 48 Acoustic terminal hole 49 Acoustic resistance material 51 Gasket 52 Coupler 60 Base 61 Acoustic terminal hole 68 Acoustic resistance material 70 Condenser microphone element 71 Diaphragm 72 Diaphragm holder 73 Spacer 76 Fixed electrode 80 Condenser microphone element 81 Diaphragm 82 Diaphragm holder 83 Spacer 86 Fixed electrode 88 Acoustic resistance material

Claims (4)

A pair of diaphragms, a fixed electrode disposed opposite to each diaphragm with a gap, a rear acoustic resistance material disposed opposite to each other corresponding to each fixed electrode, and each rear part Having a space formed between acoustic resistance materials,
Each diaphragm functions as an acoustic terminal, and each diaphragm is a manufacturing method of a variable directivity condenser microphone unit in which an opening for pressure equalization leading to the space is formed.
Using an acoustic resistance measuring device having two air flow paths connected at one end to the air flow generation source in a lump, each of which is connected to a differential pressure gauge near the tips of the two air flow paths,
The diaphragm is set at the tip of one air flow path of the acoustic resistance measuring device, the reference sound resistance material is set at the tip of the other air flow path,
The tip of the one air flow path to which the diaphragm is to be set is a funnel-shaped receiving part,
The diaphragm has an outer periphery fixed to the diaphragm holder, the diaphragm integrated with the diaphragm holder is placed on the funnel-shaped receiving portion, and the air in the air flow path is sucked by the air flow generation source. And
Measure the acoustic resistance of each diaphragm based on the pressure difference between the two air flow paths,
Method of manufacturing a variable directional condenser microphone unit to the diaphragm of a suitable acoustic resistance value pairs, characterized in that incorporated into the microphone unit.   2. The method of manufacturing a variable directivity condenser microphone unit according to claim 1, wherein the air resistance values of the diaphragms forming a pair are matched. The method of manufacturing a variable directivity condenser microphone unit according to claim 1 or 2, wherein needles serving as reference air resistances are respectively disposed between the air flow source and the differential pressure gauge connecting portion in the two air flow paths. .   A pair of diaphragms arranged opposite each other with a space, a fixed electrode arranged opposite to each diaphragm, and arranged behind each other corresponding to each fixed electrode A rear acoustic resistance material and a space formed between each rear acoustic resistance material,
  Each diaphragm has a pressure equivalent opening, and each diaphragm functions as an acoustic resistance material.
  A variable directivity condenser microphone in which a variable directivity condenser microphone unit capable of adjusting directivity by adjusting the acoustic resistance between a pair of diaphragms is incorporated in a microphone case,
  The variable directivity condenser microphone unit is a variable directivity condenser microphone manufactured by the method according to any one of claims 1 to 3.

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