JP2010288047A - Unidirectional condenser microphone unit - Google Patents

Abstract

A unidirectional condenser microphone unit including a rear acoustic resistance material exhibiting a stable acoustic resistance value over a long period of time is provided.
SOLUTION: A unit case 2 having a front acoustic terminal 21 on the front side facing the sound source side and a rear acoustic terminal 22 on the rear side separated by a predetermined distance from the front acoustic terminal 21 is supported. The acoustoelectric transducer 3 is housed in which the diaphragm 31 stretched on the ring 32 and the fixed pole 33 supported by the insulating seat 34 are arranged to face each other with a spacer member interposed therebetween. A sound hole 341 for guiding the sound wave from the terminal 22 to the back side of the diaphragm 31 is formed, and the acoustic resistance material 4 is arranged on the rear surface side of the insulating seat 34 so that the sound resistance can be adjusted so as to close the sound hole 341. In the unidirectional condenser microphone unit 1A, a raised pile 41 is used for the acoustic resistance material 4.
[Selection] Figure 1

Description

  The present invention relates to a unidirectional condenser microphone unit, and more particularly to an acoustic resistance material disposed on the rear side of the unit.

  The condenser microphone unit includes a cylindrical unit case made of a metal material. However, as shown in FIG. 4, a unidirectional condenser microphone unit (hereinafter sometimes simply referred to as “microphone unit”) 1 is provided. Is a unit case having a front acoustic terminal 21 on the front side (left side in FIG. 4) that is directed to the sound source side during sound collection, and a rear acoustic terminal 22 on the rear side that is a predetermined distance away from the front acoustic terminal 21. 2 is used.

  Although only one front acoustic terminal 21 is shown in FIG. 4 for the sake of drawing, a plurality of front acoustic terminals 21 are actually provided. In this example, the unit case 2 is covered with a resonator 2a. The microphone unit 1 in this example is an exchange unit that can be attached to and detached from a microphone body (not shown), and the rear side of the unit case 2 is closed by the microphone body when in use.

  An electrostatic acoustoelectric converter 3 is accommodated in the unit case 2. The acoustoelectric converter 3 includes a diaphragm 31 that forms a variable capacitance capacitor as a pair, and a fixed pole 33.

  The diaphragm 31 is stretched around the support ring 32, and the fixed pole 33 is fixed to the front side of an insulating seat 34 made of synthetic resin, and these are arranged oppositely via a spacer ring (not shown).

  Sound holes (sound wave introduction holes) 331 and 341 included in the rear acoustic path from the rear acoustic terminal 22 to the back surface of the diaphragm 31 are formed in the fixed pole 33 and the insulating seat 34.

  Of the sound waves coming from the sound source, the sound wave that enters from the front acoustic terminal 21 acts on the front surface of the diaphragm 31, and the sound wave that enters from the rear acoustic terminal 22 acts on the back surface of the diaphragm 31 via the rear acoustic path. As a result, the microphone operates as unidirectional.

  As described in Patent Document 1, the acoustic resistance material 4 for the sound hole 341 is usually disposed on the rear surface side of the insulating seat 34. The acoustic resistance of the acoustic resistance material 4 is r, the acoustic capacity of the back air chamber 3a existing on the back side of the diaphragm 31 is s, and the sound waves entering from the rear acoustic terminal 22 are acoustic resistance r and acoustic capacity s. It is divided and added to the back surface of the diaphragm 31.

  Normally, an open-cell sponge made of urethane is used as the acoustic resistance material 4. However, in the unidirectional condenser microphone unit that requires accurate directivity, the acoustic resistance material 4 has an acoustic resistance. The resistance is adjustable, and the acoustic resistance can be finely adjusted linearly.

  Therefore, as shown in FIG. 5, a cylindrical male screw shaft 342 projects from the center of the rear surface side of the insulating seat 34, and a nut-like resistance plate 5 with a female screw is screwed onto the male screw shaft 342. Thus, the resistance plate 5 allows the degree of compression (acoustic resistance value) of the acoustic resistance material 4 to be finely adjusted linearly.

  FIG. 6A shows a state where the compression degree of the acoustic resistance material 4 is reduced, and FIG. 6A shows a state where the compression degree of the acoustic resistance material 4 is increased. According to Patent Document 2, the acoustic resistance value of the acoustic resistance material 4 can be easily matched with the acoustic resistance value of the reference unit.

Japanese Utility Model Publication No. 5-11696 JP 2005-328347 A

  According to the above conventional example, the acoustic resistance of the acoustic resistance material 4 can be finely adjusted by simply turning the resistance plate 5, but the urethane sponge used in the acoustic resistance material 4 has a reduced elastic force due to deterioration over time. There is a problem that the acoustic resistance value changes with long-term use, and consequently the acoustic characteristics of the microphone itself change.

  Therefore, in order to suppress aging degradation, heat aging treatment is applied to urethane sponge to use less physical changes, but heat aging not only takes a long time, but also introduces the equipment. Since the cost is high, it is not preferable in terms of productivity and cost.

  Therefore, an object of the present invention is to provide a unidirectional condenser microphone unit including a rear acoustic resistance material that exhibits a stable acoustic resistance value over a long period of time.

  In order to solve the above problems, the present invention provides a unit case having a front acoustic terminal on the front side directed toward the sound source side and a rear acoustic terminal on the rear side separated by a predetermined distance from the front acoustic terminal. Inside, an electrostatic acoustoelectric transducer is housed in which a diaphragm stretched on a support ring and a fixed pole supported on the front side of the insulating seat are arranged oppositely via a spacer member, A sound hole for guiding sound waves from the rear acoustic terminal to the back side of the diaphragm is formed in the insulating seat, and an acoustic resistance material can adjust the acoustic resistance so as to close the sound hole on the rear surface side of the insulating seat. In the unidirectional condenser microphone unit arranged as described above, the acoustic resistance material is made of a raised pile planted on a resistance plate arranged opposite to the rear surface of the insulating seat.

  In the present invention, the resistance plate is movable along the axial direction of the insulating seat, and part of the raised pile is deformed as the resistive plate moves in a direction approaching the insulating seat, and the acoustic Resistance is adjusted.

  According to a preferred aspect of the present invention, a male screw shaft projects from the center of the rear surface side of the insulating seat, and the resistance plate includes a nut plate having a female screw that is screwed onto the male screw shaft. . Moreover, it is preferable that a polyester fiber is used for the raised pile.

  According to the present invention, a raised pile is used as an acoustic resistance material provided on the rear acoustic terminal side, and a resistance plate in which a large number of the raised piles are planted is advanced and retracted with respect to the insulating seat so as to adjust the gap density between the piles. As a result, the acoustic characteristics are not easily changed over a long period of time, and productivity is also improved. Furthermore, by using a raised pile made of polyester, it is possible to suppress deterioration over time.

Sectional drawing which shows the internal structure of the unidirectional condenser microphone unit which concerns on embodiment of this invention. The exploded sectional view by the side of the fixed pole in the above-mentioned microphone unit. Sectional drawing which shows the adjustment state of the acoustic resistance material in the said microphone unit. Sectional drawing which shows the internal structure of the unidirectional condenser microphone unit which concerns on a prior art example. The exploded sectional view by the side of a fixed pole in the above-mentioned conventional example. Sectional drawing which shows the adjustment state of the acoustic resistance material in the said prior art example.

  Next, embodiments of the present invention will be described with reference to FIGS. 1 to 3, but the present invention is not limited thereto. Components that are considered to be the same as or the same as those in the conventional example described in FIG.

  As shown in FIG. 1, since the microphone unit 1A according to this embodiment is unidirectional, as in the conventional example, the unit case has a front side (see FIG. 4, the front acoustic terminal 21 is provided on the left side, and the unit case 2 including the rear acoustic terminal 22 on the rear side separated from the front acoustic terminal 21 by a predetermined distance is used.

  Although only one front acoustic terminal 21 is shown in FIG. 1 for the sake of drawing, a plurality of front acoustic terminals 21 are actually provided. The unit case 2 is covered with the resonator 2a, but the resonator 2a may be omitted.

  The microphone unit 1 in this example is an exchange unit that can be attached to and detached from a microphone body (not shown), and the rear side of the unit case 2 is closed by the microphone body when in use.

  Alternatively, a circuit board (not shown) may be disposed on the rear side of the unit case 2. In that case, a rear acoustic terminal is formed in the circuit board, and an FET (field effect transistor) or the like as an impedance converter is mounted.

  An electrostatic acoustoelectric converter 3 is accommodated in the unit case 2. The acoustoelectric converter 3 includes a diaphragm 31 that forms a variable capacitance capacitor as a pair, and a fixed pole 33.

  The diaphragm 31 is stretched around a support ring (diaphragm ring) 32, and the fixed pole 33 is fixed to the front side (surface side facing the diaphragm) of a synthetic resin insulating seat 34, which are not shown in the figure. Are arranged to face each other.

  In this embodiment, a female screw 2b is formed on the inner surface of the unit case 2, and the acoustoelectric transducer 3 is fixed in the unit case 2 by a lock ring 7 that is screwed into the female screw 2b. When the unit case 2 is made of, for example, an aluminum press-molded product, the unit case 2 may be fixed by caulking with the rear opening edge facing inward.

  Sound holes (sound wave introduction holes) 331 and 341 included in the rear acoustic path from the rear acoustic terminal 22 to the back surface of the diaphragm 31 are formed in the fixed pole 33 and the insulating seat 34.

  As described in the above-described conventional example, the sound wave entering from the front acoustic terminal 21 among the sound waves coming from the sound source acts on the front surface of the diaphragm 31, and the sound wave entering from the rear acoustic terminal 22 passes through the rear acoustic path. Acting on the back surface of the diaphragm 31, whereby the microphone operates as unidirectional.

  On the rear surface side of the insulating seat 34, the acoustic resistance material 4 with respect to the sound hole 341 is disposed. The acoustic resistance of the acoustic resistance material 4 is r, and the acoustic capacity of the back air chamber 3a existing on the back side of the diaphragm 31 is s. As described above, the sound wave entered from the rear acoustic terminal 22 is divided by the acoustic resistance r and the acoustic capacitance s and applied to the back surface of the diaphragm 31.

  Since the acoustic capacity s is determined at the design stage, the acoustic resistance r is adjusted in order to obtain a unidirectional polar pattern after assembly. The acoustic resistance material 4 is required to stably exhibit the adjusted acoustic resistance r over a long period of time. Therefore, in the present invention, a raised pile 41 is used as the acoustic resistance material 4.

  Also in this embodiment, as shown in FIG. 2, a cylindrical male screw shaft 342 protrudes from a central portion on the rear surface side of the insulating seat 34, and a nut-like resistance plate with a female screw is provided on the male screw shaft 342. Since 5 is provided with the structure which is screwed together, the raising pile 41 is planted on the surface side facing the insulating seat 34 of the resistance plate 5.

  Since a plurality of sound holes 341 of the insulating seat 34 are usually arranged on a concentric circle with the male screw shaft 342 as the center, the resistance plate 5 has an outer diameter that can cover all of the sound holes 341. A nut plate is used. The component denoted by reference numeral 6 is an electrode rod that is fitted to the male screw shaft 342 and is connected to the fixed pole 33 through a conductive means (not shown). The electrode rod 6 is connected to the gate of the FET. The

  For the raised pile 41, natural fibers can be used in addition to synthetic resin fibers, but polyester piles with little secular change are preferable. In this embodiment, a polyester pile of 3.3 decix and a length of 0.8 mm is employed, and electrostatic flocking is performed on the resistance plate 5. The planting density may be arbitrarily determined.

  According to this, when the resistance plate 5 is screwed into the male screw shaft 342 and rotated so as to approach the insulating seat 34 side, the tip of the raised pile 41 is changed from the state of FIG. 3A to FIG. 3B. As a result, the gap between the raised piles 41 is reduced, and as a result, the acoustic resistance value is increased.

  As described above, according to the present invention, the acoustic resistance value by the raised pile 41 can be linearly adjusted according to the screwing amount of the resistance plate 5, and the acoustic resistance value after the adjustment can be stabilized over a long period of time. Can be maintained.

  In the above-described embodiment, the raised pile 41 is implanted on the resistance plate 5 by electrostatic flocking. Alternatively, for example, a sheet in which the raised pile 41 is previously implanted may be attached to the resistance plate 5. Good.

  Further, instead of the nut plate screwing the resistance plate 5 to the male screw shaft 342, for example, a raised pile 41 is implanted in a washer plate having a plurality of petal-like spring tongue pieces in the center hole, and the washer plate is The washer plate may be engaged with the male screw shaft 342 or a support shaft corresponding thereto, and the washer plate may be locked at a predetermined position by the spring tongue piece. Such an embodiment is also included in the present invention. It is.

DESCRIPTION OF SYMBOLS 1A Condenser microphone unit 2 Unit case 21 Front acoustic terminal 22 Rear acoustic terminal 3 Acoustoelectric converter 31 Diaphragm 32 Support ring 33 Fixed pole 34 Insulation seat 331,341 Sound hole (sound wave introduction hole)
342 Male screw shaft 4 Acoustic resistance material 41 Brushed pile 5 Resistance plate

Claims (4)

Vibration stretched on a support ring in a unit case having a front acoustic terminal on the front side facing the sound source side and a rear acoustic terminal on the rear side separated from the front acoustic terminal by a predetermined distance An electrostatic acoustoelectric transducer is housed in which a plate and a fixed pole supported on the front side of the insulating seat are arranged to face each other via a spacer member, and the acoustic wave from the rear acoustic terminal is stored in the insulating seat. A unidirectional condenser microphone in which a sound hole is formed to guide the sound hole to the back side of the diaphragm, and an acoustic resistance material is arranged to adjust the acoustic resistance so as to close the sound hole on the rear surface side of the insulating seat In the unit
A unidirectional condenser microphone unit, wherein the acoustic resistance material comprises a raised pile planted on a resistance plate disposed to face the rear surface of the insulating seat.   The resistance plate is movable along the axial direction of the insulating seat, and part of the raised pile is deformed and the acoustic resistance is adjusted as the resistive plate moves in a direction approaching the insulating seat. The unidirectional condenser microphone unit according to claim 1.   2. A male screw shaft projecting substantially at the center on the rear surface side of the insulating seat, and the resistance plate comprises a nut plate having a female screw threadedly engaged with the male screw shaft. The unidirectional condenser microphone unit according to 2.   The unidirectional condenser microphone unit according to any one of claims 1 to 3, wherein polyester fibers are used for the raised pile.

Images