JP4751802B2 - Narrow directional microphone - Google Patents

Description

  The present invention relates to a narrow directional microphone in which an acoustic tube is accommodated in a microphone case, and more particularly, to a narrow directional microphone having guide means for coaxially arranging the acoustic tube with respect to the microphone case. is there.

  In a narrow directional microphone using an acoustic tube, a long acoustic tube is provided on the front acoustic terminal side of the unidirectional microphone unit. The acoustic tube has a sound wave introduction port covered with an acoustic resistance material on the tube wall, and narrows the directivity of the unidirectional microphone unit by taking sound waves from the sound wave introduction port (for example, Patent Documents 1 and 2).

  An example of the configuration will be described with reference to FIGS. 3 is a side view showing the appearance of a conventional narrow directivity microphone, FIG. 4 is a cross-sectional view taken along the line BB of FIG. 3 showing a simplified internal structure, and FIG. 5 is an enlarged cross-sectional view taken along the line CC of FIG. is there.

  As shown in FIGS. 3 and 4, in the conventional narrow directivity microphone 1B, a cylindrical microphone case 10 made of a metal material that is longer than a normal microphone is used. The tip 10f on the upper end side of the microphone case 10 in FIG. 4 is opened, and a front cap 11 formed in a grill shape is put on the opening.

  An output connector 50 is integrally attached to the rear end 10r of the microphone case 10 in FIG. Usually, as the output connector 50, the 3-pin type output connector 50 defined in EIAJ RC-5236 “Latch lock type circular connector for audio equipment” is used.

  As the microphone unit, an electrostatic unidirectional microphone unit 30 having a front acoustic terminal 31 and a rear acoustic terminal 32 is used. The unidirectional microphone unit 30 is fixed to a predetermined part in the microphone case 10 via a support member 41 made of synthetic resin.

  Inside the microphone case 10, a unidirectional microphone unit 30 divides the acoustic tube storage unit 10 </ b> A on the front end 10 f side where the acoustic tube 20 is stored and the power module unit 10 </ b> B on the rear end 10 r side where the circuit board 42 is stored. Partitioned.

  The acoustic tube 20 is inserted from the front end 10f side of the microphone case 10 until the rear end of the tube is fitted around the front acoustic terminal 31 of the unidirectional microphone unit 30, and then the rear end tube. The end is screwed to the microphone case 10.

  Although not shown, an audio output circuit including a FET (field effect transistor) as an impedance converter and a power supply circuit is mounted on the circuit board 42, and the unidirectional microphone unit 30 is provided at the gate of the FET. The extraction electrode 33 is connected via a leaf spring contact or the like (not shown). The audio output circuit of the circuit board 42 is connected to the output connector 50.

  Referring to the cross-sectional view of FIG. 5, sound wave inlets 21 are drilled in the tube wall of the acoustic tube 20 at two positions facing each other at least 180 ° in order to obtain narrow directivity and axial symmetry. An acoustic resistance material 22 is attached to the outer wall side of 20 so as to cover the sound wave introduction port 21.

  Usually, the sound wave introduction ports 21 are formed in a series of slits extending over almost the entire length of the acoustic tube 20, or a plurality of round holes are arranged in a line along the axial direction of the acoustic tube 20.

  For the acoustic resistance material 22, a felt material, a nonwoven fabric, or the like is used. Although not shown, a protective net made of a metal net or the like is provided on the outermost periphery of the acoustic tube 20 in order to improve the appearance and prevent the acoustic resistance material 22 from being touched.

  In this state, the acoustic tube 20 is inserted into the acoustic tube housing portion 10A of the microphone case 10, but the opening of the acoustic tube housing portion 10A is larger than the sound wave inlet 21 as shown in FIG. The part 12 is formed as a slit hole along the circumferential direction. Although not shown, a sound wave introduction port for the rear acoustic terminal 32 is formed on the rear end side of the acoustic tube housing portion 10A.

JP 62-118698 A JP-A-8-19087

  By the way, as shown in FIG. 6, when the axis of the acoustic tube 20 is decentered in the acoustic tube housing portion 10A, one acoustic resistance member 22 is sandwiched between the microphone case 10 and the acoustic resistance. Becomes higher than the other acoustic resistance material 22, and the axial symmetry is impaired.

  In order to prevent this, conventionally, a spacer ring 13 as shown in FIG. 7 is fitted into the opening of the microphone case 10 on the tip 10f side. The spacer ring 13 includes a sleeve 13a on the inner surface of which the outer periphery of the distal end of the acoustic tube 20 is fitted.

  A male screw 13b is formed on the outer surface side of the sleeve 13a. Correspondingly, female screws 10c and 11b are formed in the opening on the tip 10f side of the microphone case 10 and the skirt portion 11a of the front cap 11, respectively. It is assembled as follows.

  First, while fitting the tip of the acoustic tube 20 into the sleeve 13 a, the lower half of the male screw 13 b is screwed into the female screw 10 c on the microphone case 10 side, so that the acoustic tube 20 is coaxial with the microphone case 10. Then, the front cap 11 is attached to the microphone case 10 by screwing the female screw 11b on the front cap 11 side with the upper half of the male screw 13b of the sleeve 13a.

  Thereby, narrow directivity and axial symmetry are ensured. However, not only a separate part called the spacer ring 13 is required, but also the spacer ring 13, the microphone case 10 and the front cap 11 must be threaded, which increases the cost. There is also a problem that assembly takes time.

  Accordingly, an object of the present invention is to make it possible to arrange the acoustic tube coaxially with respect to the microphone case while having a simple configuration in the narrow directivity microphone in which the acoustic tube is accommodated in the microphone case. is there.

  In order to solve the above-mentioned problems, the present invention is characterized in that, as described in claim 1, a cylindrical microphone case having an acoustic tube storage portion on the distal end side, and a tube wall covered with an acoustic resistance material A cylindrical acoustic tube having a sound wave inlet and housed in the acoustic tube housing portion of the microphone case, and a unidirectional microphone unit disposed on the rear end side of the acoustic tube in the microphone case. A narrow directional microphone including a front cap on a front end opening of the microphone case, wherein the front cap is provided on a grill-like cap body and a peripheral edge of the cap body, and has an outer diameter of the microphone case. A skirt portion that is approximately the same diameter as the inner diameter of the tip opening portion and is closely fitted in the tip opening portion. The acoustic tube in contact with the front end portion of the tube is characterized by tapered for aligning coaxially is formed with respect to the microphone case.

  In the present invention, as described in claim 2, the front cap is preferably made of an elastic body. Moreover, as described in claim 3, it is preferable that the front cap has conductivity. More preferably, the front cap has both elasticity and conductivity.

  According to the present invention, the outer diameter of the front cap attached to the tip of the microphone case is fitted to the periphery of the front end opening of the microphone case so that the outer diameter is substantially the same as the inner diameter of the tip opening of the microphone case. The front cap is attached to the microphone by providing a skirt portion to be joined, and forming a taper on the inner diameter surface of the skirt portion to contact the tip portion of the acoustic tube and align the acoustic tube coaxially with the microphone case. The acoustic tube can be arranged coaxially with respect to the microphone case simply by being attached to the tip of the case.

  In this case, since the front cap functions as a shock mount by forming the front cap with an elastic body, vibration noise can be reduced. Further, by forming the front cap from a conductive material, the shielding property is enhanced, and the generation of noise due to external electromagnetic waves or the like can be suppressed.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1A is an external front view showing a narrow directivity microphone according to an embodiment of the present invention, FIG. 1B is a cross-sectional view taken along line AA of FIG. FIG. 2 is a cross-sectional view similar to FIG. 1B showing the microphone case and the front cap separately. Components that may be regarded as the same as or the same as those of the conventional example described with reference to FIGS. 3 to 5 are denoted by the same reference numerals.

  1 and 2, a narrow microphone 1A according to the present invention also uses a cylindrical microphone case 10 made of a metal material such as a brass alloy, which is longer than a normal microphone. The front end 10f of the microphone case 10 in FIG. 1 is opened, and a front cap 100 is put on the front end opening 10d.

  An output connector 50 is integrally attached to the rear end 10r of the lower end side of the microphone case 10 in FIG. The output connector 50 may be an output connector defined in EIAJ RC-5236 “Latch lock type circular connector for audio equipment”. The output connector 50 is connected to a phantom power source (not shown).

  Also in the present invention, the electrostatic unidirectional microphone unit 30 having the front acoustic terminal 31 and the rear acoustic terminal 32 is used as the microphone unit. The microphone case 10 is partitioned by the unidirectional microphone unit 30 into an acoustic tube storage portion 10A on the front end 10f side and a power module portion 10B on the rear end 10r side in which the circuit board 42 is stored.

  Although not shown, the circuit board 42 is equipped with a sound output circuit including an FET (field effect transistor) as an impedance converter, a power supply circuit, etc., as in the conventional example described above. The extraction electrode of the unidirectional microphone unit 30 is connected to the gate via a leaf spring contactor or the like. The audio output circuit of the circuit board 42 is connected to the output connector 50.

  The acoustic tube 20 is disposed in the acoustic tube storage portion 10A. As in the above-described conventional example, the acoustic tube 20 is covered with an acoustic resistance material 22 at least at two positions 180 ° opposite to the tube wall as shown in FIG. 5 in order to obtain narrow directivity and axial symmetry. A broken sound wave inlet 21 is provided. Although not shown, a protective net is provided around the acoustic resistance material 22.

  In this example, the unidirectional microphone unit 30 is mounted in a tube end portion at the rear end of the acoustic tube 20 via a shock mount 43 made of a rubber elastic body, and the rear end of the acoustic tube 20 is the microphone case 10. It is screwed to.

  In the present invention, the front cap 100 is provided with guide means for coaxially arranging the acoustic tube 20 with respect to the microphone case 10.

  The front cap 100 includes a cap main body 110 formed in a grill shape, and a skirt portion 120 provided integrally on the periphery of the cap main body 110. The outer diameter of the skirt 120 is substantially the same as the inner diameter φ1 of the tip opening 10d of the microphone case 10, and the outer diameter surface 121 of the skirt 120 is closely fitted to the tip opening 10d.

  In this example, the tip opening 10d is thinner than the other parts of the microphone case 10 so that the skirt 120 can be inserted between the tip opening 10d and the tip of the acoustic tube 20. Is formed.

  On the other hand, a taper is formed on the inner diameter surface 122 of the skirt portion 120 so as to contact the tip portion of the acoustic tube 20 and align the acoustic tube 20 coaxially with the microphone case 10.

  That is, assuming that the outer diameter of the distal end portion of the acoustic tube 20 is φ2, the inner diameter of the open end side of the skirt portion 120 is φa, and the inner diameter of the base portion of the skirt portion 120 on the cap body 110 side is φb, the inner diameter surface 122 of the skirt portion 120. Are tapered such that φb <φ <2φa.

  According to this, the acoustic tube 20 is coaxially positioned with respect to the microphone case 10 by inserting the skirt portion 120 of the front cap 100 into the tip opening portion 10d of the microphone case 10 and fixing it with an adhesive or the like. Can do.

  Further, by forming at least the skirt portion 120 of the front cap 100 from an elastic material such as rubber, the skirt portion 120 becomes a shock mount, so that vibration noise can be reduced. In addition, it is preferable in terms of productivity that the cap body 110 and the skirt portion 120 are integrally formed of an elastic material.

  Further, by forming the front cap 100 with a conductive material, the shielding performance of the entire microphone can be improved, and the generation of noise due to external electromagnetic waves or the like can be effectively suppressed. It is more preferable to form the front cap 100 with a material having both elasticity and conductivity. Examples of this type of material include a trade name “Soft Shield 4000, 5000 series” manufactured by Taiyo Wire Mesh Co., Ltd. it can.

(A) The external appearance front view which shows the narrow directivity microphone which concerns on embodiment of this invention, (b) The sectional view on the AA line of (a) which simplifies and shows the internal structure. Sectional drawing similar to FIG.1 (b) which shows a microphone case and a front cap separately. The side view which shows the external appearance of the conventional narrow directivity microphone. The BB sectional drawing of FIG. 3 which shows an internal structure simplified. The CC sectional view taken on the line of FIG. Sectional drawing similar to FIG. 5 which shows the state in which the acoustic tube is eccentric. The expanded sectional view which shows the front-end | tip part of the microphone case in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A Narrow directivity microphone 10 Microphone case 10A Acoustic tube storage part 10B Power module part 10d Tip opening part 20 Acoustic tube 21 Sound wave introduction port 22 Acoustic resistance material 30 Unidirectional microphone unit 31 Front acoustic terminal 32 Rear acoustic terminal 42 Circuit Board 50 Output connector 100 Front cap 110 Cap body 120 Skirt part 121 Outer diameter surface 122 Inner diameter surface

Claims (3)

Cylindrical microphone case having an acoustic tube housing part on the distal end side, and a cylindrical acoustic wave housed in the acoustic tube housing part of the microphone case having a sound wave introduction port covered with an acoustic resistance material on the tube wall In a narrow directional microphone including a tube and a unidirectional microphone unit disposed on the rear end side of the acoustic tube in the microphone case, and a front cap is placed on a front end opening of the microphone case ,
The front cap is provided on the periphery of the grill-like cap body and the cap body, and has an outer diameter that is substantially the same as the inner diameter of the tip opening of the microphone case and is closely fitted in the tip opening. A skirt portion is provided, and an inner diameter surface of the skirt portion is formed with a taper for contacting the tip portion of the acoustic tube and coaxially aligning the acoustic tube with the microphone case. Narrow directional microphone.   The narrow directional microphone according to claim 1, wherein the front cap is made of an elastic body.   The narrow directional microphone according to claim 1, wherein the front cap has conductivity.

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