JPH0677394U - Sound pressure gradient type microphone - Google Patents

Abstract

(57) [Summary] [Purpose] To improve sensitivity and frequency response in the low frequency range. [Structure] A diaphragm 2 arranged on the front surface of a back electrode plate 3, a front acoustic terminal 19 arranged on the front side of the diaphragm 2, and a rear acoustic member arranged on the rear side of the back electrode plate 3. In a sound pressure gradient type microphone having a terminal 20 and performing a sound-mechanical conversion by taking in a sound pressure difference between the acoustic terminals 19 and 20, the inside and the outside between the front acoustic terminal 19 and the rear acoustic terminal 20. Baffle plates 9 and 10 having different acoustic resistances were provided in the portions.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a sound pressure gradient type microphone, and more specifically to a sound pressure gradient type microphone having improved sensitivity and frequency characteristics by providing a plurality of baffles between front and rear sound pressure terminals.

[0002]

[Prior art]

 The sound pressure gradient type microphone has two or more acoustic terminals, takes in the sound pressure difference between these acoustic terminals to give a pressure difference across the diaphragm, and performs acoustic-mechanical conversion by this pressure difference. In order to increase the sensitivity of such a sound pressure gradient type microphone, a large driving force for the vibrating plate is required, and in order to obtain a large driving force, it is sufficient to increase the distance between the acoustic terminals. However, in a high frequency band where the half-wavelength of the sound wave is the same as the distance between the acoustic terminals, there is a frequency where the driving force becomes 0, so if the distance between the acoustic terminals is unnecessarily increased, the high frequency response range It lowers the limit. Therefore, it has been proposed that a leaky baffle plate made of an acoustic resistance material be provided between the acoustic terminals to increase the frequency response in the middle and high frequencies to increase the driving force for the diaphragm.

There is also known a method of increasing a frequency response in a low frequency range by using a leaky baffle plate made of an acoustic resistance material. However, as the acoustic resistance is increased, a driving force is similarly increased. A frequency at which is 0 is generated. The frequency at which the driving force becomes 0 is generally called a dip.

[0004]

[Problems to be solved by the device]

 As described above, in order to increase the sensitivity of the microphone, a large driving force is required, but unreasonably increasing the distance between acoustic terminals lowers the high frequency limit of the frequency response. Even if a leaky baffle plate is used to increase the frequency response in the middle and low frequencies, increasing the acoustic resistance of the baffle also lowers the high frequency limit of the frequency response. .

The present invention has been made in view of the circumstances of the prior art as described above, and an object thereof is to improve the sensitivity and the frequency response in the low frequency range by using a baffle. Type microphone.

[0006]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention provides a diaphragm arranged in front of the back plate, a front acoustic terminal arranged in front of the diaphragm, and a rear side of the back plate. In a sound pressure gradient type microphone that has a rear acoustic terminal that is arranged, and that performs acoustic-mechanical conversion by taking in the sound pressure difference between the both acoustic terminals, between the front acoustic terminal and the rear acoustic terminal. It has a configuration in which a plurality of baffles having different acoustic resistances are provided in the radial direction.

[0007]

[Action]

 According to the above configuration, the outer baffle of the plurality of baffles can equivalently lengthen the distance between the acoustic terminals in the low frequency range, thereby obtaining a larger driving force and improving the sensitivity. In addition, the frequency response in the low frequency range can be increased.

[0008]

【Example】

 An example of a preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a unit portion of a sound pressure gradient type microphone according to an embodiment. In the figure, a microphone unit 1 of a sound pressure gradient type microphone is connected to a case 4 equipped with a diaphragm 2 and a back electrode plate 3 provided behind it, and an impedance converter (not shown) connected to the back electrode plate 3. It is mainly composed of an electrode pin 5 connected to the part.

A large number of ventilation holes 6 are provided on the outer peripheral side of the case 4, and a plurality of openings 8 for introducing sound waves are also formed on the front surface portion 7 of the case 4 on the inner peripheral side. The front surface 7 of the case 4 is provided with an inner baffle plate 9 made of an acoustic resistance material made of a donut-shaped nylon mesh of, for example, about # 200 so as to cover the air holes 6. An outer baffle plate 10 made of a porous sheet having a thickness of 2 mm is provided at an end portion of the outer periphery of the case 4 facing the front surface portion 7. In this embodiment, the porous sheet used for the outer baffle plate 10 is a donut-shaped porous sheet commercially available from Kanebo Co., Ltd. under the trade name “Belita D-3320” and fixed with an adhesive 11. is doing.

The diaphragm 2 is arranged behind the front surface portion 7 of the case 4 in parallel with the front surface portion 7 of the case 4 via the diaphragm supporting ring 12, and the diaphragm 2 and the back electrode plate 3 are connected to each other. A spacer 13 is provided therebetween, and the outer peripheral side of the back electrode plate 3 on the rear side is fixed to the case 4 by a lock ring 14. The electrode pin 5 is fixed to the insulating seat 15 with a lock nut 16. An acoustic resistance material 17 is attached by an adjuster 18 so that its acoustic resistance can be adjusted. As a result, the front surface side of the case 4 functions as the front acoustic terminal 19, and the rear surface side thereof functions as the rear acoustic terminal 20.

The microphone unit 1 configured as described above has a connector sleeve 22 provided with a connector 21 as shown in a front view of the internal structure of FIG. 2 and a side view of the internal structure of FIG. Is stored in. On the upper surface of the connector sleeve 22, a wind screen 23 formed by pressing a wire mesh or the like into a substantially bottomed cylindrical body is attached via a cylindrical microphone case 24.

The microphone unit 1 is held in the windscreen 23 by supporting the legs of the band-shaped unit holder 25 wound around the outer periphery of the case 4 on the unit stand 26. The unit stand 26 supports a circuit board 27 on the bottom of which an electrical structure such as an amplifier circuit including a transformer is mounted. The unit stand 26 is attached to the connector sleeve 22 via a shock mount 28 and a supporting member 29, which are shock absorbing members made of an elastic material. Although not shown, the output signal from the circuit board 26 is connected so as to be output to the connector 21 side. Reference numeral 30 is a protective band provided so as to cover the wind screen 23.

As described above, in this embodiment, the inner baffle plate 9 formed of # 200 nylon mesh is provided on the inner side, and the outer baffle plate 10 formed by the 2 mm-thick porous sheet is provided on the outer side. The acoustic resistance value of the outer baffle plate 10 is larger than that of the inner baffle plate 9. In this way, by adding a baffle plate with high acoustic resistance to the outside and passing a part of the sound wave flowing from the front acoustic terminal 19 to the rear acoustic terminal 20 through the outer baffle plate 10, the acoustic terminal distance is equivalent in the low frequency range. Longer, and a larger driving force can be obtained.

That is, a characteristic diagram in which the frequency response of the sound pressure gradient type microphone configured as described above is measured is shown in FIG. 4, and the frequency of the sound pressure gradient type microphone having only the inner baffle plate without the outer baffle plate is shown. The response characteristic diagram is shown in FIG. Comparing these characteristics, when taking 0 ° as an example, it can be seen that the dip in the dip portion caused by the driving force becoming 0 in the high frequency range is considerably smaller than that in FIG. Also, it can be seen that the frequency response is increased by about 2 dB around 60 Hz. The sensitivity at the reference frequency was −32.9 dB / Pa in this embodiment, whereas the sensitivity at the reference frequency of only the inner baffle plate was −33.8 dB / Pa, which was 0.9 dB / Pa. Was up.

In this embodiment, both baffle plates are configured so that the acoustic resistance of the outer baffle plate 10 is larger than the acoustic resistance of the inner baffle plate 9, but they may be reversed depending on the conditions. However, if the inner baffle plate 9 is omitted and a baffle of the same size is configured only by the outer baffle plate 10, the acoustic resistance is too large, and a large drop occurs in the high frequency response region in the front. Therefore, it is not preferable in terms of characteristics to form the baffle plate only on the outside.

[0017]

[Effect of device]

 As is clear from the above description, according to the present invention configured as described above, since a plurality of baffles having different acoustic resistances are provided in the radial direction between the front acoustic terminal and the rear acoustic terminal, a large baffle is provided. It becomes possible to obtain driving force, which can improve sensitivity and frequency response in the low frequency range.

[Brief description of drawings]

FIG. 1 is a sectional view showing a microphone unit of a sound pressure gradient microphone according to an embodiment of the present invention.

FIG. 2 is a front sectional view showing a partially cutaway internal structure of a sound pressure gradient microphone according to an embodiment of the present invention.

FIG. 3 is a side view of the sound pressure gradient microphone shown in FIG.

FIG. 4 is a measurement diagram showing frequency response characteristics of the microphone unit according to the embodiment of the present invention.

FIG. 5 is a measurement diagram showing frequency response characteristics of a microphone unit according to a conventional example.

[Explanation of symbols]

 1 Microphone unit 2 Vibration plate 3 Back electrode plate 4 Case 6 Vent hole 7 Case front part 8 Opening 9 Inner baffle plate 10 Outer baffle plate 11 Adhesive 19 Front acoustic terminal 20 Rear acoustic terminal

Claims (1)

[Scope of utility model registration request] 1. A diaphragm arranged in front of the back plate, all acoustic terminals arranged in front of the diaphragm, and a rear acoustic terminal arranged in rear of the back plate. In a sound pressure gradient type microphone that captures a sound pressure difference between both acoustic terminals and performs acoustic-mechanical conversion, a plurality of baffles having different acoustic resistances in the radial direction between the front acoustic terminal and the rear acoustic terminal. A sound pressure gradient type microphone characterized by being provided individually.