JP4893380B2 - Condenser microphone device - Google Patents

Description

  The present invention relates to an improvement of a condenser microphone device (including an electret condenser microphone device), and suppresses the generation of impact sound when the condenser microphone device is impacted by hitting the condenser microphone device against an object.

If the microphone device is accidentally bumped into an object or the like during use, the diaphragm of the microphone device may vibrate (pick up) due to the vibration of the microphone device. As a conventional technique for suppressing the generation of such an impact sound, there has been a technique described in Patent Document 1 below. This is because two microphone elements are mounted on the handset of a telephone or wireless device, and the sound collecting part of one microphone element is masked with a resin sheet to make the sound sensitivity lower than that of the other microphone element. On the other hand, arithmetic processing is performed so that the sensitivities of both microphone elements are equal and the output signals of both microphone elements cancel each other. According to this, since the amount of sound picked up by both microphone elements is greatly different, it is not canceled much by the arithmetic processing, and the vibration sound due to impact is largely canceled by the arithmetic processing because the amount picked up by both microphone elements is equal. As a result, good sensitivity can be obtained with respect to the sound, and the sensitivity with respect to the impact is lowered, so that the generation of the impact sound can be suppressed.
JP 2001-36607 A

  According to the technique described in Patent Document 1, it is necessary to mask the sound collecting portion of one microphone element with a resin sheet. The present invention has been made in view of the above points, and an object of the present invention is to provide a condenser microphone device that does not require masking.

  The condenser microphone device according to the present invention accommodates the first and second capacitor-type elements having the same characteristics with the diaphragm and the back plate facing each other with an appropriate gap therebetween in the same package with the same surface facing the same direction. And forming an acoustic hole for receiving a sound wave from outside at a position where the sound wave incident surface of the first capacitor type element of the package faces, and the acoustic hole is acoustically blocked by the first capacitor type element. Therefore, the sound wave from the outside is taken in from the acoustic hole of the package and vibrates the diaphragm of the first capacitor type element, and the sound wave generated by the vibration of the diaphragm propagates through the internal space of the package. Thus, the diaphragm of the second capacitor type element is vibrated.

  According to the present invention, the external sound wave is taken from the acoustic hole of the package and vibrates the diaphragm of the first capacitor type element, and the sound wave generated by the vibration of the diaphragm propagates through the internal space of the package and Since the diaphragm of the second capacitor type element is vibrated, the sound incident directions of the first and second capacitor type elements are opposite to each other with respect to the sound from the outside. Accordingly, the diaphragms of the first and second capacitor elements are displaced in opposite phases with respect to the back plate with respect to the sound from the outside. On the other hand, since the first and second capacitor-type elements are arranged with the same surface facing in the same direction, when an external shock is applied to the capacitor microphone device, the diaphragms of both elements are inertial due to the shock. Displace in the same direction. Therefore, if the output signals of the first and second capacitor-type elements are subtracted, the sound from the outside is enhanced, and the impact sound due to the impact from the outside is attenuated. As a result, a condenser microphone device having a low sensitivity to an impact while ensuring a good sensitivity to sound is realized. Therefore, even if the condenser microphone device is hit against an object, an impact sound is hardly generated. Thereby, it is possible to suppress the generation of impact sound without using masking.

  The capacitor microphone device of the present invention accommodates the impedance converters of the first and second capacitor type elements and a subtractor for subtracting the output signals of both the impedance converters in the package. The subtracted output can be output to the outside of the package.

  The capacitor microphone device of the present invention accommodates the impedance converters of the first and second capacitor type elements in the package, and outputs the converted outputs of both the impedance converters from the package to the outside. Can be configured. In this way, a balanced output type is obtained, so that even if noise enters from the outside in the middle of both output signal lines, the signal from both output signal lines is subtracted by the subsequent circuit to reduce the noise from the outside. Can be removed.

  In the capacitor microphone device according to the present invention, the first and second capacitor-type elements may each be constituted by a MEMS (Micro Electro Mechanical Systems) element.

Embodiment 1
Embodiment 1 of the condenser microphone device of the present invention is shown in FIG. 1A is a cross-sectional view in which the entire condenser microphone device is halved along the longitudinal direction (a cross-sectional view taken along the line AA in FIG. 1B), and FIG. 1B is a view in which the cover plate of the package (casing) is removed. (C) is a bottom view. The capacitor microphone device 10 is configured by accommodating and arranging capacitor microphone elements 12 and 14 and an impedance conversion and calculation LSI 16 in a package 11 made of metal or the like. The package 11 is configured by assembling a bottom plate 11a, a side plate 11b, and a lid plate 11c. An acoustic hole 27 is formed in the bottom plate 11a as the only opening through which the internal space 26 of the package 11 communicates with the external space. When the condenser microphone device 10 is mounted on a device such as a mobile phone terminal, it is mounted so that the acoustic hole 27 is not blocked. The capacitor microphone elements 12 and 14 and the impedance conversion and calculation LSI 16 are fixed on the bottom plate 11a in the package 11 with an adhesive. The condenser microphone element 12 is disposed so as to close the acoustic hole 27.

  The capacitor microphone elements 12 and 14 have structures and characteristics that are equal to each other, and can be configured by, for example, well-known silicon microphones using MEMS elements. FIG. 1 also shows a case where the capacitor microphone elements 12 and 14 are formed of silicon microphones. That is, the capacitor microphone element 12 is configured by disposing a diaphragm 22 and a back plate 24 opposite to each other with an appropriate gap in an opening 20 of a substrate 18 made of silicon or the like. A plurality of through holes 24 a are formed in the surface of the back plate 24, and sound waves generated by the vibration of the diaphragm 22 are transmitted through the through holes 24 a and propagated to the internal space 26 of the package 11. . The opening 20 is arranged coaxially with the acoustic hole 27 of the package 11, and the sound wave incident surface of the condenser microphone element 12 (referred to as a surface on which sound waves are incident. In this embodiment, the lower surface of the diaphragm 22 corresponds). 27 A sound wave from the outside is incident from the acoustic hole 27 and vibrates the diaphragm 22 through the opening 20. The diameter of the acoustic hole 27 is preferably formed to be equal to the diameter of the opening 20. Alternatively, the diameter of the acoustic hole 27 can be made slightly smaller than the opening 20 in consideration of ease of assembly (a slight deviation of the axis is allowed). A minute through hole 22 a for adjusting the atmospheric pressure is formed at the peripheral edge of the diaphragm 22. The air pressure adjusting through hole 22a constitutes an internal space 26 of the package 11 (this internal space 26 constitutes a back air chamber for the condenser microphone element 12. Here, the “back air chamber” refers to the diaphragm as viewed from the incident side of the sound wave. The space on the back side is communicated with the outside air through the opening 20 and the acoustic hole 27, and the air pressure in the internal space 26 of the package 11 is made equal to the outside air pressure. The atmospheric pressure adjusting through hole 22a hardly transmits sound waves. A terminal 23 of the diaphragm 22 and a terminal 25 of the back plate 24 are formed on the upper surface of the capacitor microphone element 12 at a position away from the back plate 24.

  The capacitor microphone element 14 is configured similarly to the capacitor microphone element 12. That is, the capacitor microphone element 14 is configured by disposing a diaphragm 34 and a back plate 36 opposite to each other with an appropriate gap in an opening 32 of a substrate 30 made of silicon or the like. A plurality of through holes 36 a are formed in the surface of the back plate 36, and sound waves generated by the diaphragm 22 of the condenser microphone element 12 and propagated to the internal space 26 of the package 11 pass through the through holes 36 a and pass through the diaphragm 34. It is configured to vibrate. A minute through hole 34 a for adjusting the atmospheric pressure is formed at the peripheral edge of the diaphragm 34. The air pressure adjusting through hole 34a functions to make the air pressure of the internal space 33 of the opening 32 (the internal space 33 forms a back air chamber for the condenser microphone element 14) equal to the air pressure of the internal space 26 of the package 11. . Therefore, the internal space 33 of the condenser microphone element 14 includes the pressure adjusting through hole 34a of the diaphragm 34, the through hole 36a of the back plate 36, the internal space 26 of the package 11, the through hole 24a of the back plate 24 of the condenser microphone element 12, and the diaphragm 22. Are communicated with the outside air through the air pressure adjusting through hole 22a, the opening 20, and the acoustic hole 27, and are adjusted to be equal to the outside air pressure. The atmospheric pressure adjusting through hole 34a hardly transmits sound waves. A terminal 35 of the diaphragm 34 and a terminal 37 of the back plate 36 are formed on the upper surface of the capacitor microphone element 14 at a position away from the back plate 36. The terminals 23, 25, 35, 37 of the capacitor microphone elements 12, 14 are connected to the corresponding terminals 16 a, 16 b, 16 c, 16 d of the impedance conversion and calculation LSI 16 through signal lines 15, 17, 19, 21, respectively. .

  The operation of the capacitor microphone device 10 having the above configuration will be described. FIG. 2 shows the operation when the sound wave S1 is incident from the outside. At this time, the sound wave S1 from the outside enters from the acoustic hole 27 of the package bottom plate 11a, and vibrates the diaphragm 22 through the opening 20 of the capacitor microphone element 12. When the diaphragm 22 vibrates, a sound wave S2 is generated on the back side of the diaphragm 22 due to the vibration. The sound wave S2 passes through the through hole 24a of the back plate 24, passes through the internal space 26 of the package 11, passes through the through hole 36a of the back plate 36 of the capacitor microphone element 14, and vibrates the diaphragm 34. FIG. 3 shows output signal waveforms of the capacitor microphone elements 12 and 14 at this time. The condenser microphone element 12 and the capacitor microphone element 14 have the sound wave incident directions opposite to each other, so that the output signal waveforms are in opposite phases. Therefore, if the two output signals are subtracted, an output having an amplitude larger than that of each output signal can be obtained.

  FIG. 4 shows the operation when an impact is applied from the outside. At this time, since the impact is applied to the diaphragms 22 and 34 of the capacitor microphone elements 12 and 14 in the same direction, the diaphragms 22 and 34 are displaced in the same direction due to inertia due to the impact. FIG. 5 shows output signal waveforms of the capacitor microphone elements 12 and 14 at this time. Since the diaphragms 22 and 34 are displaced in the same direction by the inertia due to the impact, the output signal waveforms are in phase with each other. Therefore, if the two output signals are subtracted, an output having an amplitude smaller than that of each output signal can be obtained.

  FIG. 6 is a circuit diagram (conceptual diagram) of the capacitor microphone device 10. A dashed line 11 is a portion configured in the package 11, and a dotted line 16 is a portion configured in the impedance conversion and calculation LSI 16. The output signal of the capacitor microphone element 12 is subjected to impedance conversion and gain adjustment by the impedance conversion and gain adjuster 40. The output signal of the capacitor microphone element 14 is subjected to impedance conversion and gain adjustment by an impedance conversion and gain adjuster 42. The output signals of the impedance converter and gain adjusters 40 and 42 are subtracted from each other by the subtractor 44. The output signal of the subtracter 44 is output from the package 11 through the output signal line 45 as an output signal (microphone output) of the capacitor microphone device 10.

  The volume of the internal space 26 of the package 11 constituting the back air chamber of the condenser microphone element 12 and the internal space 33 of the opening 32 constituting the back air chamber of the condenser microphone element 14 are different (internal space 26> internal space 33). Therefore, the sensitivity is different between the capacitor microphone element 12 and the capacitor microphone element 14 (the diaphragm is easier to move when the internal space is larger, so the sensitivity of the capacitor element 12 is higher). Therefore, the signal gain is adjusted by the impedance conversion and gain adjusters 40 and 42 so that the output signal of the subtractor 44 becomes the minimum value with respect to the impact. As a result, the output signal level of the subtracter 44 decreases with respect to impact and increases with respect to sound. Therefore, while ensuring good sensitivity to sound, the sensitivity to impact is low, and the generation of impact sound when subjected to impact can be suppressed.

<< Embodiment 2 >>
Embodiment 2 of the condenser microphone device of the present invention will be described. In this case, the output signals of the two capacitor microphone elements are taken out from the package of the capacitor microphone device as a balanced output. The mechanical configuration in the package is the same as that shown in FIG. A circuit diagram (conceptual diagram) is shown in FIG. 7 that are the same as those in FIG. 6 are denoted by the same reference numerals. A dashed line 11 is a portion configured in the package 11, and a dotted line 16 is a portion configured in the impedance conversion and calculation LSI 16. The output signal of the capacitor microphone element 12 is subjected to impedance conversion and gain adjustment by the impedance conversion and gain adjuster 40. The output signal of the capacitor microphone element 14 is subjected to impedance conversion and gain adjustment by an impedance conversion and gain adjuster 42. The output signals of the impedance conversion and gain adjusters 40 and 42 are output from the package 11 through the output signal lines 46 and 48 as the balanced output of the capacitor microphone device 10. These balance outputs are subtracted from each other in a subsequent circuit and used as a microphone output. According to this, even if noise is mixed into the output signal lines 46 and 48 of the balanced output from the outside, it is removed by subtraction in the subsequent circuit, so that a signal with good SN can be obtained. The impedance conversion and gain adjustment in the gain adjusters 40 and 42 are the same as those described in the first embodiment.

  Although the acoustic hole 27 is circular in FIG. 1, it can be formed in other shapes. For example, when the opening 20 of the substrate 18 of the capacitor microphone element 12 is a quadrangle, the acoustic hole 27 can be formed in a quadrangle accordingly. In FIG. 1, the condenser microphone elements 12 and 14 have the diaphragms 22 and 34 arranged on the lower side and the back plates 24 and 36 arranged on the upper side, but conversely, the diaphragms 22 and 34 are arranged on the upper side and the back plate 24 is arranged. , 36 can be arranged on the lower side. In FIG. 1, the capacitor microphone elements 12 and 14 are formed of MEMS elements. However, individual parts can be assembled.

It is a figure which shows Embodiment 1 of the capacitor | condenser microphone apparatus of this invention. It is a schematic diagram which shows operation | movement of this capacitor | condenser microphone apparatus 10 when a sound wave is incident on the condenser microphone apparatus 10 of FIG. 1 from the outside. FIG. 3 is an output signal waveform diagram of capacitor microphone elements 12 and 14 by the operation of FIG. 2. It is a schematic diagram which shows operation | movement of this capacitor | condenser microphone apparatus 10 when an external impact is added to the capacitor | condenser microphone apparatus 10 of FIG. FIG. 5 is an output signal waveform diagram of the capacitor microphone elements 12 and 14 by the operation of FIG. 4. FIG. 2 is a circuit diagram (conceptual diagram) in the first embodiment of the capacitor microphone device 10 of FIG. 1. It is a circuit diagram (conceptual figure) in Embodiment 2 of the capacitor | condenser microphone apparatus 10 of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Condenser microphone apparatus, 11 ... Package, 12, 14 ... Capacitor microphone element (capacitor-type element), 16 ... Impedance conversion and calculation LSI, 22, 34 ... Diaphragm, 24, 36 ... Back plate, 26 ... Inside of package Space, 27 ... acoustic hole of package, 40,42 ... impedance converter and gain adjuster (impedance converter), 44 ... subtractor, 45,46,48 ... output signal line.

Claims (4)

The diaphragm and the back plate are arranged opposite to each other with an appropriate gap, and the first and second capacitor-type elements having the same characteristics are accommodated in a common package with the same surface facing in the same direction,
Forming an acoustic hole for capturing sound waves from outside at a position where the sound wave incident surface of the first capacitor type element of the package faces;
The acoustic hole is acoustically blocked by the first capacitor-type element, and external sound waves are taken in from the acoustic hole of the package to vibrate the diaphragm of the first capacitor-type element. A condenser microphone device in which sound waves generated by the vibration of the diaphragm propagate through the internal space of the package to vibrate the diaphragm of the second capacitor-type element.   The package includes an impedance converter for each of the first and second capacitor-type elements and a subtractor for subtracting the output signals of both impedance converters. The condenser microphone device according to claim 1, wherein the capacitor microphone device is output.   2. The capacitor microphone according to claim 1, wherein each of the impedance converters of the first and second capacitor-type elements is accommodated in the package and the converted outputs of both the impedance converters are output from the package to the outside. apparatus.   4. The capacitor microphone device according to claim 1, wherein each of the first and second capacitor-type elements is configured by a MEMS (Micro Electro Mechanical Systems) element. 5.

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