JP5419254B2 - Microphone unit - Google Patents

Description

  The present invention relates to a microphone unit, and more particularly to a microphone unit in which a vibration film is shifted with respect to an opening of a casing constituting the microphone unit.

  There is known a microphone unit that receives sound from outside and converts the sound into an electric signal. Since such a microphone unit is used as, for example, a voice input device of a mobile phone or other mobile terminal, it is preferable that the microphone unit be small (thin). In particular, in recent years, with the thinning of mobile phones and the like, the demand for the size required for each component has become stricter. For example, the microphone unit is required to have a thickness of 1.5 mm or less. Therefore, a technique for reducing the size (thinning) of the microphone unit has been proposed.

  For example, in Japanese Patent Application Laid-Open No. 2001-54196 (Patent Document 1), a fixed electrode and a vibrating membrane are arranged at a constant interval, and an audio signal given to the vibrating membrane is detected by a change in capacitance between them. An electret condenser microphone configured as described above is disclosed. According to Japanese Patent Laying-Open No. 2001-54196 (Patent Document 1), in an electret condenser microphone, the fixed electrode, the vibration film, and the semiconductor element are accommodated in parallel in a box-shaped case made of an insulating material.

  Japanese Unexamined Patent Application Publication No. 2007-306125 (Patent Document 2) discloses a card-type MEMS microphone. According to Japanese Patent Laying-Open No. 2007-306125 (Patent Document 2), a card-type MEMS microphone is formed by a substrate having a first through hole and a second through hole, a diaphragm electrode, and a back air chamber. A MEMS chip that is mounted at a position where the space surrounds the outlet of the first through hole, converts a sound signal propagated to the diaphragm electrode into an electric signal, and a substrate surface opposite to the side on which the MEMS chip is mounted. And an acoustic resistance material mounted at a position covering the first through hole. The substrate has a terminal that transmits an electrical signal output from the MEMS chip to the electronic device, and has a card shape that can be attached to and detached from the electronic device. The second through hole is a through hole through which the sound signal is diffracted and propagated to the vibrating membrane electrode.

  Japanese Unexamined Patent Application Publication No. 2007-124449 (Patent Document 3) discloses a microphone. According to Japanese Patent Laying-Open No. 2007-124449 (Patent Document 3), there is provided a conductive electrode and a movable diaphragm electrode disposed opposite to the conductive electrode with a gap constituting a part of the first sound pressure passage. Is formed as a so-called MEMS composed of mechanical parts and electric parts formed on a semiconductor substrate. An electrostatic attractive force is generated by applying a voltage between the conductive electrode and the movable diaphragm electrode, and the movable diaphragm electrode is attracted to the conductive electrode, thereby opening or closing the first sound pressure passage.

  Japanese Unexamined Patent Publication No. 2000-165999 (Patent Document 4) discloses a semiconductor electret condenser microphone. According to Japanese Unexamined Patent Publication No. 2000-165999 (Patent Document 4), a microphone includes a semiconductor chip on which necessary electronic circuits are formed, an electrode layer laminated on the surface of the semiconductor chip via an insulating layer, and the electrode. An insulating film formed on the layer, a vibrating film attached to an insulating ring, and a predetermined space between the vibrating film and the insulating film are provided between the ring and the insulating film. A spacer layer. The vibrating membrane is obtained by electretizing a polymer FEP film having an electrode layer formed on one side.

Japanese Unexamined Patent Application Publication No. 2006-14267 (Patent Document 5) discloses a condenser microphone. According to Japanese Patent Laying-Open No. 2006-14267 (Patent Document 5), the support is located above the fixed electrode and insulates the fixed electrode from the metal case, and is positioned between the uppermost stage in the metal case and the support. It is electrically connected to the metal case and the support, and is equipped with a FET for amplifying and converting the potential change due to the change in capacitance between the diaphragm and the fixed electrode due to the vibration of the diaphragm to an electrical signal A printed circuit board having a plurality of sonic inlets perforated, delaying the transmission of sound waves flowing into the sonic inlet of the printed circuit board, and fixing the fixed electrode to the gate of the FET formed on the printed circuit board. Connect electrically.
JP 2001-54196 A JP 2007-306125 A JP 2007-124449 A JP 2000-165999 A JP 2006-14267 A

  In the above microphone unit, the thickness of the vibration film itself for detecting sound waves is about several μm. However, the side wall portion that supports the vibration film has a thickness of about 400 μm, and the size (thickness) of the side wall portion accounts for a large proportion of the overall size (thickness) of the microphone unit. Further, in the microphone unit, it is preferable not to dispose the diaphragm directly under the opening in order to prevent malfunction caused by dust entering from the opening to which sound is input and adhering to the diaphragm. That is, it is preferable that the vibration film does not overlap directly below the opening. In other words, it is preferable that the vibration film and the side wall portion are arranged so that the vibration film cannot be seen from the outside of the microphone unit through the opening. For this reason, the microphone unit is configured such that the sound input from the opening reaches the vibrating membrane across the side wall.

  However, when the thickness of the entire microphone unit is reduced, the inner wall surface of the casing constituting the microphone unit and the side wall portion supporting the vibrating membrane come close to or in contact with each other, and the sound path is narrowed. Since the acoustic impedance increases as the cross-sectional area of the sound path decreases, the acoustic characteristics of the microphone unit deteriorate. For example, there is a problem that a flat high frequency characteristic cannot be obtained due to a decrease in the resonance frequency of the space determined from the internal space in the microphone unit.

  The present invention has been made to solve the above problems, and a main object of the present invention is to arrange the vibration membrane at a position shifted from the opening of the casing, and to close the side wall to the casing. Alternatively, it is to provide a microphone unit whose acoustic characteristics are not deteriorated even if it abuts.

  In order to solve the above problems, according to one aspect of the present invention, a microphone unit is provided. The microphone unit includes a housing including a first space inside. The housing includes a housing opening that communicates the first space with the outside. The microphone unit includes a vibration film disposed in the first space, an electric circuit unit that outputs an electric signal based on vibrations of the vibration film, and a sidewall part disposed in the first space and thicker than the vibration film. And further comprising. The side wall portion is disposed by shifting the vibration film from below the housing opening by supporting the periphery of the vibration film. The side wall includes a side wall opening that communicates the second space above the diaphragm and the outside.

Preferably, the side wall opening is positioned on the housing opening side of the side wall.
Preferably, the side wall opening includes a notch formed by forming at least a part of the side wall part lower than the other part.

  Preferably, the side wall portion includes four side walls. The notch is formed by forming a height of a part of one of the side walls lower than the other part of the side wall.

Preferably, the side wall opening includes a hole formed in the side wall.
Preferably, a housing | casing contains the inner wall face which comprises the ceiling of 1st space. At least a part of the side wall is in contact with the inner wall surface.

  As described above, according to the present invention, there is provided a microphone unit in which the vibration film is disposed at a position shifted from the opening of the housing, and the acoustic characteristics are not deteriorated even when the side wall portion and the housing are close to or in contact with each other. Provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[Embodiment 1]
<Overall Configuration of Audio Signal Transmitting / Receiving Device 100A>
FIG. 1 is a block diagram showing an overall configuration of an audio signal transmitting / receiving apparatus 100A according to the present embodiment. Audio signal transmitting / receiving apparatus 100A according to the present embodiment is, for example, a mobile phone. As illustrated in FIG. 1, the audio signal transmission / reception device 100A includes a microphone unit 110A, an amplification unit 120, an addition unit 130, a speaker 140, and a transmission / reception unit 170. Each of the blocks constituting audio signal transmitting / receiving apparatus 100A according to the present embodiment is realized by a dedicated hardware circuit such as a gain adjusting apparatus, an adder, or a wireless communication apparatus, for example.

  However, the audio signal transmitting / receiving apparatus 100A may be a mobile phone or a personal computer having a CPU (Central Processing Unit) or a storage device, and each block may be realized as a part of the function of the CPU. . That is, a configuration may be adopted in which a control program for realizing the following functions is stored in the storage device, and the function of each block is realized by the CPU reading and executing the control program from the storage device.

  In FIG. 1, the amplification unit 120 is realized by an amplifier circuit using an operational amplifier or the like, and is connected to the microphone unit 110 </ b> A, the addition unit 130, and the transmission / reception unit 170. The amplifying unit 120 amplifies the transmission audio signal input from the microphone unit 110 </ b> A and outputs the amplified audio signal to the transmitting / receiving unit 170 and the adding unit 130.

  The transmission / reception unit 170 is realized by a wireless communication device such as an antenna (not shown), and is connected to the amplification unit 120 and the addition unit 130. The transmission / reception unit 170 receives the reception audio signal and transmits the transmission audio signal. More specifically, the transmission / reception unit 170 transmits the transmission audio signal input from the amplification unit 120 to the outside, receives the reception audio signal from the outside, and outputs it to the addition unit 130.

  Adder 130 is connected to transmitter / receiver 170, amplifier 120, and speaker 140. The adding unit 130 adds the reception audio signal input from the transmission / reception unit 170 and the transmission audio signal input from the amplification unit 120 to generate an addition signal, and outputs the addition signal to the speaker 140.

  The speaker 140 converts the addition signal input from the addition unit 130 into a received voice and outputs it.

<Configuration of Microphone Unit 110A>
Next, the configuration of the microphone unit 110A according to the present embodiment will be described. FIG. 2 is a front sectional view showing the microphone unit 110A according to the present embodiment.

  As shown in FIG. 2, the microphone unit 110 </ b> A includes a microphone substrate 621 and an upper housing 611 stacked on the microphone substrate 621.

  A vibration film 113 and an ASIC (Application Specific Integrated Circuit) 240 are disposed on the upper surface of the microphone substrate 621. The ASIC 240 performs processing such as amplifying a signal based on the vibration of the vibration film 113. The ASIC 240 is preferably arranged near the vibration film 113. When the signal based on the vibration of the vibration film 113 is weak, the influence of external electromagnetic noise can be suppressed as much as possible, and the SNR (Signal to Noise Ratio) can be improved. Further, the ASIC 240 may have a configuration in which not only an amplifier circuit but also an AD converter or the like is built in and digitally output.

  The upper housing 611 forms a first space for enclosing (accommodating) the side wall 112 </ b> A, the vibration film 113, and the ASIC 240 with the microphone substrate 621. A housing opening 611A for transmitting sound waves (sound vibration) from the outside of the microphone unit 110A to the first space is formed at one end of the upper housing 611. The sound wave reaches the upper surface of the vibrating membrane 113 by passing through the first opening through the housing opening 611A.

  The ASIC 240 is disposed on the side of the vibration film 113 on the side opposite to the housing opening 611A so as not to block the sound wave propagating from the housing opening 611A to the vibration film 113. It is preferable.

  The vibration film 113 is supported by the side wall portion 112 </ b> A disposed on the microphone substrate 621. Hereinafter, the vibration film 113 and the side wall portion 112A that supports the vibration film 113 will be described. FIG. 3A is a perspective view of the side wall 112A according to the present embodiment, and FIG. 3B is a plan view of the side wall 112A according to the present embodiment. FIG. 4 is a front sectional view showing the vibration film 113 and the side wall 112A.

  As shown in FIGS. 1 to 4, the vibration film 113, the side wall portion 112 </ b> A, and the ASIC 240 constitute a vibration detection unit 111.

  Referring to FIGS. 2 to 4, housing opening 611A is formed at one end of upper housing 611 of microphone unit 110A. The side wall portion 112A supports the periphery of the vibration film 113, thereby disposing the vibration film 113 at a position shifted from the lower side of the housing opening 611A. As described above, since the vibration film 113 is arranged so as to be shifted from the lower side of the housing opening 611A, the vibration film 113 is not directly exposed to the outside of the microphone unit 110A. As a result, dust such as dust or dust can be prevented from adhering to the vibration film 113.

  The outer peripheral surface of the side wall portion 112A according to the present embodiment is composed of four planes. However, the side wall portion 112A may be composed of four side walls. The side wall 112A has an opening formed on the housing opening 611A side. More specifically, in the side wall 112A according to the present embodiment, a part of the side wall on the housing opening 611A side is formed lower than the height of the other side wall. In other words, the side wall 112A is formed with a notch 112B on the housing opening 611A side.

  From the viewpoint of securing the cross-sectional area of the sound path and the miniaturization of the microphone unit 110A, the size of one side (width) of the notch 112B is 0.2 mm or more, and the diameter of the vibrating membrane 113 (0.5 to 1 mm) or less. Or it is preferable that the height of the notch part 112B is 0.2-0.3 mm.

  Thus, since the notch 112B is formed on the side of the housing opening 611A in the side wall 112A according to the present embodiment, the side wall 112A is surrounded by the notch 112B and the inner wall surface of the upper housing 611. The sound wave easily reaches the vibration film 113 through the gap space. Here, the inner wall surface of the upper housing 611 constitutes the ceiling of the first space.

  As shown in FIG. 4, since the side wall portion of the normal side wall portion is hermetically sealed, the sound wave propagates from above the vibration membrane 113 to the vibration membrane 113 beyond the side wall portion 112 </ b> A. That is, the sound pressure Pf is transmitted from the direction of the arrow X in FIG. However, in the side wall portion 112A according to the present embodiment, the side wall portion 112A and the inner wall surface of the upper housing 611 are in contact with or close to each other, and a notch portion 112B is formed on the housing opening 611A side. Therefore, the sound pressure Pf is transmitted from the arrow direction Y in FIG. 4 to the space (second space) above the vibration film 113 surrounded by the side wall 112A.

  As a result, as shown in FIG. 2, even when the side wall 112 </ b> A is brought into contact with the inner wall surface (the ceiling of the first and second spaces) of the upper housing 611, it is possible to propagate sound waves to the vibration film 113. become. That is, the side wall portion 112A according to the present embodiment can propagate sound waves to the vibration film 113 while increasing the strength of the microphone unit 110A by contacting the microphone substrate 621 and the inner wall surface of the upper housing 611. Is possible.

  That is, the microphone unit 110A according to the present embodiment reduces the strength of the microphone unit 110A by reducing the height of at least a part of the side wall 112A in the direction of the housing opening 611A with respect to the vibration film 113. Therefore, the cross-sectional area of the sound path from the housing opening 611A to the diaphragm 113 can be ensured, and the microphone unit 110A can be made thin and have good acoustic characteristics.

  Furthermore, the microphone unit 110A according to the present embodiment can reduce the internal space volume of the housing by shortening the sound path length, thereby keeping the resonance frequency high. The volume of the microphone unit 110A can be reduced. Further, the notch 112B of the side wall 112A can be easily formed by, for example, etching.

<Modification of side wall>
FIG. 5 is a front sectional view showing a modification of the side wall portion according to the present embodiment. As shown in FIG. 5, the side wall 112C according to this modification has a hole 112D formed on the side of the housing opening 611A of the side wall 112C. As described above, in the microphone unit 110A according to this modification, the sound wave from the outside passes through the space surrounded by the housing opening 611A and propagates to the first space. Then, the sound wave propagated to the first space passes through the space surrounded by the hole 112D and propagates to the vibration film 113.

  From the viewpoint of securing the cross-sectional area of the sound path, and from the viewpoint of reducing the size of the microphone unit 110A, the size (or diameter) of one side of the hole 112D is 0.2 mm or more, preferably 0.2 to 0.3 mm. Preferably there is.

  As described above, since the hole 112D is formed on the side of the housing opening 611A in the side wall 112C according to this modification, the sound wave passes through the space surrounded by the hole 112D to the vibration film 113. It can be reached. That is, in the side wall portion 112C according to this modification, the hole portion 112D is formed on the housing opening 611A side, so that the upper side of the vibration film 113 surrounded by the side wall portion 112C from the arrow direction Y in FIG. The sound pressure Pf is transmitted to the space (second space).

  As a result, as shown in FIG. 5, even when the upper surface of the side wall portion 112C is brought into contact with or close to the inner wall surface (the ceiling of the first and second spaces) of the upper housing 611, the sound wave is propagated to the vibration film 113. It becomes possible to make it. That is, the side wall portion 112C according to the present embodiment can propagate sound waves to the vibration film 113 while increasing the strength of the microphone unit 110A by contacting the microphone substrate 621 and the inner wall surface of the upper housing 611. Is possible.

  The side wall 112C according to this modification can be easily formed with a side wall opening by forming a hole 112D in the side wall 112C.

[Embodiment 2]
Next, a second embodiment of the present invention will be described. The audio signal transmitting / receiving apparatus 100B according to the present embodiment has a differential microphone unit 110B.

  FIG. 6 is a block diagram showing an overall configuration of audio signal transmitting / receiving apparatus 100B according to the present embodiment. Audio signal transmitting / receiving apparatus 100B according to the present embodiment is, for example, a mobile phone. As illustrated in FIG. 6, the audio signal transmission / reception device 100B includes a differential microphone unit 110B, an amplification unit 120, an addition unit 130, a speaker 140, and a transmission / reception unit 170. The configuration of audio signal transmitting / receiving apparatus 100B is similar to that of the first embodiment described above, and therefore detailed description will not be repeated.

<Configuration of differential microphone unit 110B>
Hereinafter, the differential microphone unit 110B according to the present embodiment will be described. FIG. 7 is a front sectional view showing the periphery of the vibration detection unit 111.

  As shown in FIGS. 6 and 7, the differential microphone unit 110 </ b> B according to the present embodiment includes a vibration detection unit 111. The differential microphone unit 110B according to the present embodiment removes background noise by acquiring an acoustic difference.

  The vibration detection unit 111 includes a vibration film 113, a side wall portion 112A, and an ASIC described later. The vibration detection unit 111 vibrates with sound pressures (amplitudes of sound waves) Pf and Pb from two directions reaching the vibration film 113, and generates an electrical signal corresponding to the vibrations. That is, the differential microphone unit 110B receives the transmitted voice transmitted from two directions and converts it into an electrical signal.

  In the differential microphone unit 110B according to the present embodiment, the vibration film 113 is structured to receive the sound pressures Pf and Pb from both the upper and lower sides, and the vibration film 113 vibrates according to the sound pressure difference (Pf−Pb). For this reason, when sound pressures of the same magnitude are simultaneously applied to both sides of the vibration film 113, the two sound pressures cancel each other out at the vibration film 113, and the vibration film 113 does not vibrate. Conversely, when there is a difference in sound pressure applied to both sides, the vibration film 113 vibrates due to the sound pressure difference.

  And since the structure of the vibration detection part 111 containing the side wall part 112A, the vibration film 113, and the ASIC 240 is the same as that in Embodiment 1, detailed description is not repeated here.

  That is, also in the differential microphone unit 110B according to the present embodiment, the side wall portion 112A and the inner wall surface of the upper housing 612 are in contact with or close to each other, and the cutout portion 112B is formed on the housing opening 612A side. Therefore, the sound pressure Pf is transmitted from the arrow direction Y in FIG. 7 to the space (second space) above the diaphragm 113 surrounded by the side wall 112A. Alternatively, as shown in FIG. 5, since the hole 112D is formed on the side of the housing opening 612A of the side wall 112C, the upper side of the vibration film 113 surrounded by the side wall 112A from the arrow direction Y in FIG. The sound pressure Pf is transmitted to the space (second space).

  However, in the differential microphone unit 110B according to the present embodiment, the sound pressure Pb is transmitted from the direction of arrow Z in FIG. 7 to the space (second space) below the vibration film 113 surrounded by the side wall 112A. Come.

<Noise removal principle of differential microphone unit 110B>
Next, the principle of noise removal of the differential microphone unit 110B will be described. FIG. 8 is a graph showing the relationship between the sound pressure P and the distance R from the sound source. As shown in FIG. 8, the sound wave attenuates as it travels through a medium such as air, and the sound pressure (the intensity and amplitude of the sound wave) decreases. The sound pressure is inversely proportional to the distance from the sound source, so the sound pressure P is related to the distance R from the sound source.
P = k / R (1)
It can be expressed as. In equation (1), k is a proportionality constant.

  As is clear from FIG. 8 and Expression (1), the sound pressure (the amplitude of the sound wave) is abruptly attenuated at a position close to the sound source (left side of the graph), and gradually decreases as the distance from the sound source is increased. That is, the sound pressure transmitted to two positions (d0 and d1, d2 and d3) that are different by a distance from the sound source is greatly attenuated from a distance d0 to d1 where the distance from the sound source is small (P0-P1). In d2 to d3 where the distance from the sound source is large, there is not much attenuation (P2-P3).

  When the differential microphone unit 110B according to the present embodiment is applied to an audio signal transmitting / receiving apparatus 100B typified by a mobile phone, the uttered voice from a speaker is generated from the vicinity of the differential microphone unit 110B. Therefore, the sound pressure of the uttered voice of the speaker is greatly attenuated between the sound pressure Pf reaching the upper surface of the vibration film 113 and the sound pressure Pb reaching the lower surface of the vibration film 113. That is, for the speech voice from the approaching speaker, there is a large difference between the sound pressure Pf reaching the upper surface of the vibration film 113 and the sound pressure Pb reaching the lower surface of the vibration film 113.

  On the other hand, far away background noise exists in a position where the sound source is far from the differential microphone unit 110B as compared with the voice of the speaker. Therefore, the sound pressure of background noise hardly attenuates between Pf that reaches the upper surface of the vibration film 113 and the sound pressure Pb that reaches the lower surface of the vibration film 113. That is, regarding the background noise, the difference between the sound pressure Pf reaching the upper surface of the vibration film 113 and the sound pressure Pb reaching the lower surface of the vibration film 113 is small.

  FIG. 9 is a graph showing the relationship between the distance R from the sound source converted into logarithm and the sound pressure P output from the microphone converted into logarithm (dB: decibel). The dotted line indicates the characteristics of the normal microphone unit, and the solid line indicates the characteristics of the differential microphone unit 110B according to the present embodiment.

  As shown in FIG. 9, the sound pressure level (dB) detected and output by the differential microphone unit 110B according to the present embodiment is greatly reduced as compared with a normal microphone unit as the distance from the sound source increases. Show properties. That is, in the differential microphone unit 110B according to the present embodiment, the sound pressure level decreases more significantly as the distance from the sound source increases than in the normal microphone unit.

  7 to 9, since the difference in sound pressure (Pf−Pb) of the background noise received by the diaphragm 113 is very small, the noise indicating the background noise generated by the differential microphone unit 110B. The signal is very small. On the other hand, since the difference (Pf−Pb) in the sound pressure of the speaker's speech received by the diaphragm 113 is large, the speech signal indicating the speech generated by the differential microphone unit 110B is growing. That is, the differential microphone unit 110B can output an utterance signal mainly indicating the utterance voice.

<Configuration of differential microphone unit 110B>
Next, the configuration of the differential microphone unit 110B according to the present embodiment will be described. 10 is a front sectional view showing the differential microphone unit 110B according to the present embodiment, and FIG. 11 is a sectional view taken along line XI-XI in FIG.

  As shown in FIGS. 10 and 11, the differential microphone unit 110 </ b> B includes a microphone substrate 622. The microphone substrate 622 includes the first substrate opening 622A and the second substrate opening 622B facing one surface, and the vibration film 113 via the first substrate opening 622A and the second substrate opening 622B. A substrate internal passage 622C communicates with the lower space and the outside.

  The differential microphone unit 110B according to the present embodiment includes an upper housing 612 that covers one surface of the microphone substrate 622 (the upper surface of the microphone substrate 622). The upper housing 612 has a first housing opening 612A and a second housing opening 612B. The upper housing 612 forms a first space for surrounding (accommodating) the side wall 112 </ b> A, the vibration film 113, and the ASIC 240 with the microphone substrate 622.

  That is, the differential microphone unit 110B according to the present embodiment includes the vibration detection unit 111. The vibration detection unit 111 is disposed at a position covering all of the first substrate opening 622A. Further, the vibration film 113 of the vibration detection unit 111 is disposed at a position covering the first substrate opening 622A.

  The sound wave propagating from the outside reaches the upper surface of the vibrating membrane 113 through the first housing opening 612A and the first space. In addition, sound waves propagating from the outside reach the lower surface of the vibration film 113 through the second housing opening 612B and the substrate internal passage 622C.

  As described above, the configuration of the vibration detection unit 111 including the side wall 112A, the vibration film 113, and the ASIC 240 is the same as that in the first embodiment, and thus detailed description thereof will not be repeated here.

  Since the differential microphone unit 110B is configured in this way, the sound pressure Pf of the sound wave incident from the first housing opening 612A is applied to the upper surface of the vibration film 113. The sound pressure Pb of the sound wave incident from the first housing opening 612B is applied to the lower surface of the vibration film 113. Therefore, the vibration film 113 vibrates based on the difference between the sound pressure Pf and the sound pressure Pb.

  Here, in order to obtain good differential microphone characteristics, adhesion between the microphone substrate 622 and the side wall portion 112A is important. If there is an acoustic leak between the microphone substrate 622 and the side wall portion 112A, the sound pressure entering from the second substrate opening 622B cannot be transmitted to the vibration film 113, and good differential microphone characteristics cannot be obtained. . In this embodiment, since all four sides of the lower surface of the side wall 112A that holds the vibration film 113 are in close contact with the upper surface of the microphone substrate 622 in the first substrate opening 622A, this one surface is acoustically treated with a sealing material or the like. By taking countermeasures against leakage, it is possible to obtain good differential microphone characteristics without variation and to obtain a microphone unit that is resistant to environmental changes.

  Therefore, according to differential microphone unit 110B in the present embodiment, sound pressure difference is obtained by inputting sound waves at two points on upper housing 612, that is, first housing opening 612A and second housing opening 612B. Can be detected. Moreover, a small and lightweight microphone unit can be realized by mounting the differential microphone unit 110 </ b> B composed of one vibration film 113 at a high density.

  The sound wave arrival time from the first housing opening 612A to the upper surface of the vibration film 113 may be configured to be equal to the sound wave arrival time from the second housing opening 612B to the lower surface of the vibration film 113. . In order to equalize the sound wave arrival time, for example, the path length of the sound wave from the first housing opening 612A to the vibrating membrane 113 and the path length of the sound wave from the second housing opening 612B to the vibrating membrane 113 are: You may comprise so that it may become equal. The path length may be, for example, the length of a line connecting the centers of the cross sections of the path. Preferably, the path length ratio is equal to ± 20% (in the range of 80% to 120%), the internal space volume of the case on the side communicating with the case opening 612A across the vibration film 113, and the case By making the internal space volume of the casing on the side communicating with the opening 612B equal to ± 50% (50% or more and 150% or less), the acoustic impedance from the casing opening 612A to the diaphragm 113, and the casing opening Since the acoustic impedance from 612B to the vibration film 113 can be made equal, the differential microphone characteristic particularly in the high frequency band can be improved.

  With this configuration, the sound pressure (gain) reaching the vibration film 113 from the first housing opening 612A and the housing opening 612B, and the first housing opening 612A and the second housing opening 612B. The arrival time, that is, the phase of the sound wave reaching the vibration film 113 can be made uniform, and a more accurate noise removal function can be realized.

  As described above, the sound pressure is rapidly attenuated at a position close to the sound source (left side of the graph in FIG. 4), and gradually decreases at a position far from the sound source (right side of the graph in FIG. 4). Therefore, regarding the sound wave with respect to the voice of the speaker, the sound pressure Pf transmitted to the upper surface of the vibration film 113 and the sound pressure Pb transmitted to the lower surface of the vibration film 113 are greatly different. On the other hand, regarding the sound wave with respect to the surrounding background noise, the difference between the sound pressure Pf transmitted to the upper surface of the vibration film 113 and the sound pressure Pb transmitted to the lower surface of the vibration film 113 becomes very small.

  Since the difference between the sound pressures Pf and Pb of the background noise received by the vibration film 113 is very small, the sound pressure for the background noise is almost canceled by the vibration film 113. On the other hand, since the difference between the sound pressures Pf and Pb of the uttered voice of the speaker received by the diaphragm 113 is large, the sound pressure for the uttered voice is not canceled out by the diaphragm 113. In this way, the differential microphone unit 110B uses the ASIC 240 to output an audio signal obtained by vibrating the vibrating membrane 113 as a transmission audio signal.

  As described above, in the present embodiment, as shown in FIG. 10, even when the side wall portion 112 </ b> A is brought into contact with the inner wall surface of the upper housing 612, the sound wave can be propagated to the vibration film 113. . That is, the side wall 112A according to the present embodiment propagates sound waves to the vibration film 113 while increasing the strength of the differential microphone unit 110B by contacting the microphone substrate 622 and the inner wall surface of the upper housing 612. It is possible.

  That is, the differential microphone unit 110B according to the present embodiment reduces the height of at least a part of the side wall 112A in the direction of the housing opening 612A with respect to the vibration film 113, thereby reducing the differential microphone unit 110B. It is possible to secure the cross-sectional area of the sound path from the housing opening 612A to the vibration film 113 without reducing the strength of the differential microphone unit 110B, and to achieve both a reduction in the thickness of the differential microphone unit 110B and good acoustic characteristics. I can do it.

  In other words, the differential microphone unit 110B according to the present embodiment can keep the resonance frequency high by shortening the sound path length. In addition, the volume of the differential microphone unit 110B can be reduced. Further, the notch 112B of the side wall 112A can be easily formed by, for example, etching.

  As described above, also in the differential microphone unit 110B according to the present embodiment, as shown in FIG. 5, the hole 112D may be formed on the side of the housing opening 611A of the side wall 112C. Thus, the side wall opening can be easily formed.

  In the above-described embodiment, the microphone substrate 622 is formed by laminating a plurality of substrates, and is configured to include upper and lower substrate layers with a substrate internal passage 622C extending in a direction parallel to the surface of the microphone substrate 622 interposed therebetween. It may be.

  As a material of the microphone substrate 622, for example, a glass epoxy substrate (FR4), a BT resin substrate, a ceramic substrate, a silicon substrate, a glass substrate, or the like can be used.

  When configuring the microphone unit 110B, the difference in linear expansion coefficient between the vibration film 113 and the side wall portion 112A and the upper layer substrate on which the diaphragm 113 is mounted is required to be as small as possible. Stress is applied to the vibration film 113 due to thermal distortion, causing a change in sensitivity of the microphone and malfunction.

  Therefore, when the vibration film 113 and the side wall portion 112A formed of a silicon material are used, the material of the microphone substrate 622, in particular, the upper layer side substrate on which the vibration film 113 and the side wall portion 112A are mounted is a silicon substrate or silicon. It is preferable to use a glass substrate or a ceramic substrate having the same linear expansion coefficient.

  In particular, when the vibration film 113 and the side wall portion 112A are flip-chip mounted on the microphone substrate 622, the stress generated by the difference in linear expansion coefficient directly affects the vibration film 113. For the upper substrate side on which the vibration film 113 and the side wall portion 112A are mounted, it is preferable to use a silicon substrate, or a glass substrate or a ceramic substrate having the same linear expansion coefficient as silicon.

  Further, when the side wall portion 112A is in contact with the upper housing 612, the difference in coefficient of linear expansion between the vibrating membrane 113, the side wall portion 112A, and the upper housing 612 is required to be as small as possible. When this occurs, stress due to thermal strain is applied to the vibration film 113, causing a change in sensitivity of the microphone and an operation failure.

  Therefore, when using the vibration film 113 and the side wall portion 112A made of a silicon material, it is possible to use a silicon substrate, a glass substrate having a linear expansion coefficient equal to silicon, or a ceramic substrate as the material of the upper housing 612. preferable.

  Note that, by appropriately selecting the material of the microphone substrate 622, a method for reducing the stress strain of the vibration film 113 caused by the difference in linear expansion coefficient is not only in the case where the side wall portion 112 has an opening, but also in the side wall portion 112. Even a normal configuration having no opening is applicable.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a block diagram showing an overall configuration of an audio signal transmitting / receiving apparatus according to Embodiment 1. FIG. 2 is a front cross-sectional view showing the microphone unit according to Embodiment 1. FIG. 2 is a perspective view and a plan view of a side wall part according to Embodiment 1. FIG. It is front sectional drawing which shows a vibration film and a side wall part. FIG. 6 is a front sectional view showing a modification of the side wall portion according to the first embodiment. 6 is a block diagram showing an overall configuration of an audio signal transmitting / receiving apparatus according to Embodiment 2. FIG. It is front sectional drawing which shows a vibration detection part periphery. It is a graph which shows the relationship between the sound pressure P and the distance R from a sound source. It is the graph which showed the relationship between what converted the distance R from a sound source into the logarithm, and what converted the sound pressure P which a microphone outputs into a logarithm (dB: decibel). 5 is a front sectional view showing a differential microphone unit according to Embodiment 2. FIG. It is XI-XI sectional drawing in FIG.

Explanation of symbols

  100A, 100B audio signal transmission / reception device, 110A microphone unit, 110B differential microphone unit, 111 vibration detection unit, 112A, 112C side wall, 112B notch, 112D hole, 113 vibration membrane, 120 amplification unit, 130 addition unit, 140 Speaker, 170 Transmission / reception unit, 611, 612 Upper housing, 611A, 612A First opening, 612B Second opening, 621, 622 Microphone substrate, 622A First substrate opening, 622B Second substrate opening Part, 622C board internal passage.

Claims (5)

A housing including a first space therein;
The housing includes a housing opening that communicates the first space with the outside.
A vibrating membrane disposed in the first space;
An electric circuit unit that outputs an electric signal based on vibration of the vibrating membrane;
A side wall portion disposed in the first space and thicker than the vibrating membrane;
The sidewall is disposed by shifting the diaphragm from below the housing opening by supporting the periphery of the diaphragm.
The side wall portion, seen contains the second space and the sidewall opening communicating with the outside of the upper of the vibrating membrane,
The said side wall opening part is a microphone unit containing the notch part formed when at least one part of the said side wall part is formed lower than another part . The side wall portion includes four side walls,
The microphone unit according to claim 1 , wherein the cutout portion is formed by forming a height of a part of any one of the side walls lower than the other part of the side wall. A housing including a first space therein;
The housing includes a housing opening that communicates the first space with the outside.
A vibrating membrane disposed in the first space;
An electric circuit unit that outputs an electric signal based on vibration of the vibrating membrane;
A side wall portion disposed in the first space and thicker than the vibrating membrane;
The sidewall is disposed by shifting the diaphragm from below the housing opening by supporting the periphery of the diaphragm.
The side wall includes a side wall opening that communicates the second space above the diaphragm and the outside,
It said sidewall opening includes a hole formed in the side wall portion, microswitch phone unit. A housing including a first space therein;
The housing includes a housing opening that communicates the first space with the outside.
A vibrating membrane disposed in the first space;
An electric circuit unit that outputs an electric signal based on vibration of the vibrating membrane;
A side wall portion disposed in the first space and thicker than the vibrating membrane;
The sidewall is disposed by shifting the diaphragm from below the housing opening by supporting the periphery of the diaphragm.
The side wall includes a side wall opening that communicates the second space above the diaphragm and the outside,
The housing includes an inner wall surface that forms a ceiling of the first space,
At least a portion of the side wall portion comes into contact with the inner wall surface, microswitch phone unit. The microphone unit according to any one of claims 1 to 4 , wherein the side wall opening is located on the housing opening side of the side wall.

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