JP2010114878A - Microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microphone capable of inputting and outputting clearer sound quality and giving exceedingly improved performance by removing vibrating components collected in principle by the microphone. <P>SOLUTION: In a housing 10 of the microphone 1, the housing 10 is separated into two chambers by a partition 13, and first and second diaphragms 11, 12 (vibrating boards) are provided in chambers A, B separated by the partition 13. A sound hole 14 is formed to let a sound wave into one chamber A, and there is no means to guide sound into another chamber B because it is hermetically sealed. Further, the chambers A, B are formed in tandem in the same direction that the sound wave is emitted from the sound hole 14. Both of the first and the second diaphragms 11, 12 are formed of fluororesin film and silicon membrane, and deformed due to the sound wave and an external vibration. The deformation causes variation in capacitance, resulting in conversion to electric signals. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to improvements in microphone technology that is a sound collection device, and more particularly, to a microphone that can remove signal components caused by unnecessary vibration.

  In general, in a situation where a microphone is used, it is unlikely that the microphone will float and be used in a space, and as shown in FIG. 18, there is a mechanical link with other structures such as some support in reality.

  Therefore, in addition to the action of reacting to the change in sound pressure due to the sound wave, which is the original purpose of the microphone, the microphone reacts by vibration propagating from a mechanical link. That is, for example, even an ECM (Electronic Capacitor Microphone) or a MEMS (Technology for manufacturing a fine structure or device using a semiconductor production process, an abbreviation of Micro Electro Mechanical Systems) microphone. However, because it uses a structure that converts the shape change of the diaphragm made of a fluororesin film or Si film into a change in capacitance and converts it into an electric signal, it is unnecessary for the purpose of a microphone that wants to react only to sound pressure. As a result, signal components resulting from vibration are superimposed, resulting in various disadvantages and performance degradation.

  The MEMS microphone has a function equivalent to that of the ECM realized by a MEMS element. That is, the material of the diaphragm (diaphragm) is different between the ECM and the MEMS microphone, but in both cases, the diaphragm is vibrated by detecting a change in sound pressure, and as a result, the capacitance between the electrode and the electrode changes. The principle of using this is the same as in the case of ECM (the present invention is assumed to be applicable to both ECM and MEMS microphone technologies).

  In the case of a MEMS microphone, sound pressure is sensed using a general Si thin film. The change of the Si thin film due to the sound pressure is read as a change in capacitance. On the other hand, in ECM, a polymer material such as a fluororesin is often used for a diaphragm for detecting sound. For this reason, soldering using a high-temperature reflow furnace could not be supported. On the other hand, since MEMS microphones are more resistant to heat than ECM, one of the advantages is that they can support reflow.

  As described above, even if it is an ECM microphone or a MEMS microphone, a structure that converts a shape change of a diaphragm made of a fluororesin film or an Si film into a change in capacitance and converts it into an electric signal. Because all the events that cause changes in the diaphragm are converted to electrical signals without being distinguished, the signal components resulting from unwanted vibrations for the purpose of microphones that want to react only to sound pressure. As a result, various drawbacks and performance degradation are caused.

  And if the unnecessary vibration in such a microphone can be eliminated, it is possible to input and output a clearer sound quality by cutting the vibration sound from the external structure that supports the microphone. It cannot be ignored on the surface. For example, in an in-vehicle speech recognition system, a vehicle interior is a place where a lot of vibrations occur, so it is considered that the speech recognition rate can be dramatically improved if the influence of vibrations can be removed. In addition, from microphones that are generally used to all mobile devices and microphones that are used in digital still cameras, etc., if the vibration component that can be said to be a drawback inherent in all of them can be eliminated, the effect is achieved. The benefits are tremendous.

  Conventional microphones have been improved from the viewpoint of reducing or suppressing vibration components by providing a vibration isolating material in the microphone housing or providing an internal structure with a vibration isolating structure. For example, an anti-vibration member is attached between a microphone case and a head cover attached to the front end of the case, and the microphone unit is fixed to the case via the anti-vibration member and provided on the side of the head cover. By providing the sound hole near the vibration isolation member, changes in air pressure in the vicinity of the vibration isolation member due to the vibration of the microphone can be avoided by outflow and inflow of air through the sound hole and propagate to the acoustic terminal. A technique for preventing vibration noise has been proposed (see Patent Document 1).

  On the other hand, in the field of electronic stethoscopes, the present inventor has made unnecessary vibrations in the vicinity of the main microphone for auscultation sound collection in order to suppress the unnecessary vibrations easily and effectively and to obtain a clear and accurate auscultation sound. For the purpose of picking up only information, an electret condenser microphone that is completely covered with a sound insulating material and shields the sound wave entering the diaphragm is provided, and this is placed close to the main microphone for auscultatory sound collection so that the mechanical coupling is dense The proposed configuration was proposed (see FIG. 10B of Patent Document 2). As a result, vibration information associated with mechanical vibrations entering the main microphone can be obtained from the auxiliary microphone with good correlation, and unnecessary vibration can be easily and effectively suppressed.

  However, in the above-described conventional microphone, the technology for providing a vibration isolating material in the microphone housing or having a vibration isolating structure inside does not remove the vibration to the last, but only prevents it. However, it cannot be used for any type of microphone, and there are problems in terms of versatility and ease of manufacture. In addition, we were able to reduce noise caused by vibrations against relatively weak vibrations such as hand-held microphones and external wind vibrations. For example, the microphones were allowed to collide with a hard article such as a table. In addition, it was impossible to prevent very strong vibrations when dropped or dropped, and it was also a problem to deal with noise caused by such vibrations.

  Further, the technique presented in Patent Document 2 is not a reduction of vibration noise, but cancels, that is, provides a new idea that could not be seen in the past, such as removal of vibration noise. It only presented the configuration of a “special microphone that shields incoming sound waves”, but did not present its theoretical basis or structural features as a new microphone.

  There exists patent document 3 as what shows a structural characteristic with respect to the above subjects. In Patent Document 3, a microphone capsule case is divided into a section having a sound hole and a section having no sound hole by a separator, and a diaphragm, a diaphragm support, and a back plate are arranged in each section, thereby having a sound hole. There is disclosed a microphone device in which a side is operated as a first microphone and a side having no sound hole is operated as a second microphone. In this microphone device, the first microphone outputs an output signal A + V1 that is the sum of the acoustic signal A from the external sound wave and the signal V1 from the external vibration, and the second microphone outputs only the signal V2 from the external vibration, By adjusting the structure and material of the microphone so that these differences A + V1−V2 by the processing circuit are equal to V1 and V2, only the acoustic signal A is extracted.

  Similarly to Patent Document 3, in Patent Documents 4 and 5, two microphones are provided, and a sound wave and a vibration component are detected on one side, and only a vibration component is detected on the other side, thereby removing the vibration component. Technology has been proposed.

JP 2008-177633 A JP 2003-102725 A International Publication No. 2006/62120 Japanese Utility Model Publication No. 4-53394 Japanese Utility Model Publication No. 1-142295

  By the way, the present inventors have doubts that a microphone device as disclosed in Patent Documents 3 to 5 has not yet been put into practical use, and as a result of earnest research, an effect of “cancel vibration” is obtained. It came to the knowledge that a considerable degree of accuracy is necessary to realize this. That is, in order to obtain a large canceling effect (-20 to -30 dB), matching with several dB is required.

  In addition, in the above microphone device using two microphones, there are individual differences in the sensitivity of the microphones when considering practical use, and in reality it is difficult that the characteristics of the two microphones are exactly the same, It is also assumed that the microphone characteristics change over time.

  Therefore, it is impossible to produce a result that can be put to practical use by simply subtracting the vibration component obtained from the other diaphragm from the sound wave and vibration component obtained from one diaphragm.

  The present invention has been proposed in order to solve the above-described problems of the prior art, and the purpose of the present invention is to be able to accurately remove the vibration component that the microphone picks up in principle, and to put it into practical use. The object is to provide a tolerable microphone.

  According to a first aspect of the present invention, there is provided a microphone that obtains an output by converting a change in shape of the diaphragm into a change in capacitance and converting it into an electric signal. The microphone has two diaphragms, and the two diaphragms have sound insulation properties. A sound wave is incident on a first chamber provided with a first diaphragm, each of which is housed in a separate chamber provided by a member and which is respectively stored in an adjacent chamber separated by a sound insulating member. A second chamber provided with a sound hole and provided with a second diaphragm is a space where sound waves are blocked, and when the sound pressure for changing the shape of the first diaphragm is p and the vibration is v , Where f (p, v) is a conversion function of the diaphragm into electric vibration, p is a sound pressure that changes the shape of the second diaphragm, and v is a vibration. When the conversion function to vibration is g (p, v), the first chamber and the second chamber have f (0, v) = g (0, v) and g (p, v, 0) = 0 is satisfied approximately, and an adaptive filter is used to approximate f (p, v) from g (p, v), which is an input signal, with a criterion of minimum square error. v) -g (p, v) = f (p, 0) is output.

  The invention of claim 2 is provided with a capacitor-type element in which a diaphragm and a back plate are arranged opposite each other with a spacer interposed therebetween, and vibration of the diaphragm is reduced to a change in capacitance and converted into an electric signal. In the microphone for obtaining the output, the two capacitor-type elements are provided, and the first and second capacitor-type elements are made of a member having a sound insulating property with the same surface directed in the same direction, and are adjacent to each other. Sound waves of the first capacitor-type elements are respectively stored in the first and second chambers provided, or provided in adjacent first and second chambers separated by a sound insulating member in a common package. A sound hole that takes in an external sound wave is formed at a position facing the incident surface, and an external sound wave is formed at a position facing the sound wave incident surface of the second capacitor-type element. When the sound pressure for changing the shape of the diaphragm in the first capacitor type element is p and the vibration is v, the conversion function of the diaphragm into electric vibration is f (p, v ), And when the sound pressure for changing the shape of the diaphragm in the second capacitor-type element is p and the vibration is v, the conversion function of the diaphragm to electric vibration is g (p, v) The first chamber and the second chamber approximately satisfy f (0, v) = g (0, v) and g (p, 0) = 0, and using an adaptive filter, By approximating f (p, v) from the input signal g (p, v) with a criterion of minimum square error, f (p, v) −g (p, v) = f (p, 0) Is output.

  In the above aspect, by providing two diaphragms in the adjacent chambers, the vibration component received by the two diaphragms is approximated as much as possible, and the chamber having the two diaphragms is separated by the sound insulation member into the first chamber. Only incident sound waves. Thus, by removing the input of only the vibration component in the diaphragm in the second chamber from the input of the sound pressure and vibration component in the diaphragm in the first chamber, the vibration component in the microphone is removed, resulting in a clearer sound quality. Can be input / output.

  In addition, the sound pressure p and the vibration v are input through the sound hole and the structure in the first diaphragm, and the vibration through the structure is input in the second diaphragm, so that only v is input. By removing the input of only the vibration component v in the second diaphragm from the input of the sound pressure p and the vibration component v in the first diaphragm, the vibration component v in the microphone can be removed and only the sound pressure p can be extracted. It becomes possible.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the first diaphragm and the second diaphragm have a sound wave incident surface facing a direction of a sound wave incident from the sound hole, And it is arranged side by side in series with respect to the incident direction.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the first capacitor-type element and the second capacitor-type element have a sound wave incident surface on a sound wave incident direction from the sound hole. And arranged side by side in the series direction with respect to the incident direction.

  In the above aspect, the first chamber having the two diaphragms and the second chamber are arranged close to each other and arranged in tandem so that the diaphragm in the first chamber and the diaphragm in the second chamber The influence of the vibration component can be approximated as much as possible. Also, the sound insulation material is sandwiched between the first chamber and the second chamber, and the structure of the first chamber itself is a sound insulation material for the second chamber, so that the sound pressure is applied to the diaphragm of the second chamber. Can be prevented from propagating.

  According to a fifth aspect of the present invention, in the first or second aspect of the invention, the first chamber and the second chamber are lateral directions that are perpendicular to the direction of the sound wave incident from the sound hole. It is characterized by being provided in parallel in the direction.

  In the above aspect, when the microphone of the present invention is applied to, for example, a MEMS microphone, since the MEMS microphone has a fine structure, the spatial positions of the two diaphragms can be brought close to each other. It is easy to approximate the vibration component propagating to the first chamber and the vibration component propagating to the second chamber. In addition, the MEMS microphone is advantageous even when it is required to be thin as a restriction when mounted on a substrate.

  According to a sixth aspect of the present invention, in the first or second aspect of the present invention, the first and second capacitor-type elements are each composed of a MEMS (Micro Electro Mechanical Systems) element. And

  In the above aspect, as described above, since the MEMS microphone has a fine structure, the spatial positions of the two diaphragms can be brought close to each other. The vibration component that propagates to the first chamber and the second chamber It is easy to approximate the propagating vibration component.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the first chamber and the second chamber are tightly coupled by a rigid member. .

  In the above aspect, the vibration component propagating to the two chambers can be approximated by tightly coupling the two chambers with a rigid material. As a result, by removing the input of the second diaphragm or the capacitor element from the input of the diaphragm or the capacitor element in the first chamber, the vibration component can be accurately removed, and the microphone is focused in principle. It is possible to accurately remove the vibration component, and to provide a microphone that can withstand practical use.

  The invention according to claim 8 is the invention according to claim 3 or 4, wherein the first chamber and the second chamber are mounted on a pedestal and are tightly coupled by a rigid member. It is supported by the support | pillar, This support | pillar is installed in the edge part opposite to the side which supports a base, It is characterized by the above-mentioned.

  In the above aspect, the two components are mounted on the pedestal, the pedestal is supported by the support column, and the physical contact point with the outside of the microphone is only the tip of the support column. All propagate from the tip of the column, so that the diaphragm or capacitor element in the two chambers behaves in the same manner as the vibration state, and the phase of the resulting electromotive force also matches.

  In addition, by connecting the chambers arranged in series tightly with a rigid material, the two diaphragms or capacitor elements vibrate in the same form even when vibration propagates from the column to the pedestal. Even in the case of series arrangement of elements, it is possible to approximate the vibration component propagating to two diaphragms or capacitor elements

  Therefore, even in a microphone having a configuration in which two diaphragms or capacitor elements are arranged in series, an electromotive force phase shift due to vibration does not occur. Therefore, the vibration component in the first diaphragm or the first capacitor element to which the sound pressure and the vibration component are input and the vibration component in the second diaphragm or the second capacitor element to which only the vibration component is input are limited. Therefore, it is possible to accurately remove the vibration component, and to accurately remove the vibration component that the microphone picks up in principle, and to provide a microphone that can withstand practical use. .

  The invention according to claim 9 is the invention according to claim 5, wherein the first chamber and the second chamber are mounted adjacent to a pedestal, and the pedestal is supported by a support column. It is characterized by being installed at the end opposite to the side supporting.

  In the above aspect, two diaphragms or two capacitor elements are mounted on the pedestal, the pedestal is supported by the support, and the physical contact point with the outside of the microphone is only the tip of the support. Since all the vibration components from the outside propagate from the tip of the column, the two diaphragms or the two capacitor elements behave in the same manner in the vibration state, and the phase of the resulting electromotive force also matches.

  According to such a microphone, even in a microphone having a configuration in which two diaphragms or two capacitor elements are arranged in parallel, a phase shift of electromotive force due to vibration does not occur. Therefore, the vibration component in the first diaphragm or the first capacitor element to which the sound pressure and the vibration component are input and the vibration component in the second diaphragm or the second capacitor element to which only the vibration component is input are limited. Therefore, it is possible to accurately remove the vibration component, and to accurately remove the vibration component that the microphone picks up in principle, and to provide a microphone that can withstand practical use. .

  The invention of claim 10 is the invention according to any one of claims 3 to 5, wherein the first chamber and the second chamber are mounted on a pedestal, and the pedestal suppresses vibration of the pedestal. A rib is provided.

  In the above aspect, by providing ribs on the pedestal, it is possible not only to obtain a vibration suppressing effect on the pedestal but also to increase the bending rigidity of the structure. Thus, by increasing the rigidity of the pedestal itself, the pedestal is less shaken, and the vibration component propagating from the pedestal to the two diaphragms or the two capacitor elements can be approximated. Accordingly, by removing the input of the second diaphragm or the second capacitor element from the input of the first diaphragm or the first capacitor element, it is possible to accurately remove the vibration component, and in principle, the microphone is used. It is possible to accurately remove the collected vibration component, and to provide a microphone that can withstand practical use.

  As described above, according to the present invention, it is possible to accurately remove a vibration component that is picked up by a microphone in principle, and it is possible to provide a microphone that can withstand practical use.

The schematic diagram which shows the schematic structure of the microphone in 1st Embodiment of this invention. The block diagram which shows the example which comprised the microphone in 1st Embodiment of this invention with the analog circuit. The block diagram which shows the example comprised with the digital circuit of the microphone in 1st Embodiment of this invention. The schematic diagram which shows the example which applied the microphone in 1st Embodiment of this invention to ECM. The schematic diagram which shows the example which applied the microphone in 1st Embodiment of this invention to the MEMS microphone. The schematic diagram which shows the modification which applied the microphone in 1st Embodiment of this invention to the MEMS microphone. The figure showing an example of the circuit composition of the microphone in a 1st embodiment of the present invention. FIG. 6 is a graph showing the experimental results of the microphone according to the first embodiment of the present invention. The image figure regarding the vibration at the time of arranging the diaphragm in 1st Embodiment of this invention in parallel. The figure which mounted and comprised the diaphragm in 2nd Embodiment of this invention in a T-shaped member. The figure which shows the time waveform of the input to the microphone in 2nd Embodiment of this invention, (a) and (b), and the figure (c) which shows a frequency characteristic. In the microphone in 2nd Embodiment of this invention, the figure (a) which shows the time waveform of the input to the microphone at the time of exciting, and the figure (c) which show a frequency characteristic. The figure which provided and provided the rib in the microphone in 2nd Embodiment of this invention. The figure which comprised the microphone in 2nd Embodiment of this invention mounted in a rigid member. The figure which shows the structure of the microphone in other embodiment of this invention. The schematic diagram which shows the structure of the conventional ECM. The schematic diagram which shows the structure of the conventional MEMS microphone. Schematic diagram showing the structure of a general microphone.

  Next, modes for carrying out the present invention (hereinafter referred to as embodiments) will be specifically described with reference to the drawings.

[1. First Embodiment]
[1-1. Schematic structure of microphone as a premise of the present embodiment]
As shown in FIG. 1A, the microphone 1 according to the present embodiment is separated into two chambers through a barrier 13 in one casing 10, and each of the chambers is separated by this barrier. The first and second diaphragms (diaphragms) 11 and 12 are provided in the chambers A and B, respectively.

  One chamber A is provided with a sound hole 14 through which sound waves are incident, and the other chamber B is in a sealed state and has no means for injecting external sound waves. The two chambers A and B are provided in tandem (in series) with respect to the direction of the sound wave incident from the sound hole 14.

  The first and second diaphragms 11 and 12 are both made of a fluororesin film and a Si film as in the prior art, and change in shape due to sound waves and external vibration. The change in shape is reduced to a change in capacitance, resulting in an electrical signal. To convert. The 1st and 2nd diaphragms 11 and 12 are provided so that the surface which receives a sound wave may be opposed to the sound wave incident from the sound hole.

  As shown in FIG. 1B, the microphone of the present invention has a sound insulation property by replacing the housing 10 and the barrier 13 provided as a single unit with the housings 10a and 10b as separate bodies. A configuration in which the chambers A and B are respectively provided in the respective housings 10a and 10b by combining the members in a column and the respective housings 10a and 10b is also possible.

  In the microphone 1 according to the present embodiment as described above, the two diaphragms are provided in the adjacent chambers so that the vibration component received by the two diaphragms is approximated as much as possible, and the chamber including the two diaphragms is A sound wave is incident only on the first diaphragm. As a result, by removing the input of only the vibration component in the second diaphragm from the input of the sound pressure and vibration component in the first diaphragm, the vibration component in the microphone is removed, and a clearer sound quality input / output is achieved. It becomes possible.

[1-2. Theoretical aspects of vibration removal]
Next, the vibration component removal in the microphone according to the present embodiment will be theoretically described. As described above, from the principle of converting the diaphragm shape change into a capacitance change and converting it into an electric signal, the function of converting sound pressure p and vibration v into electric vibration is defined as f (p, v). To do. Here, in the conventional microphone technology, the operation is often discussed within a conversion function called f (p), that is, the range of the idea that the microphone responds only to the sound pressure. It can be said that the concept of handling has not been used.

  The present invention provides a means for realizing an approximate f (p, 0) even when both independent variables p and v exist because of the conversion relationship defined in principle as f (p, v). is there. For this purpose, a second diaphragm is provided, and a similar conversion relationship g (p, v) corresponding to f (p, v) by the second diaphragm is used. The present invention generally has a structure in which the first diaphragm and the second diaphragm can approximately realize the relationship f (0, v) = g (0, v) in a frequency range where the influence of vibration v is significant. It is in the point I found. Therefore, the features of the present invention having these two diaphragms are collectively referred to as a microphone (Dual Sensing Microphone) of the present embodiment.

  In the microphone of the present embodiment, the vibration is configured to reach the two diaphragms with the same effect as much as possible. This is easily realized in a frequency range of approximately several KHz or less where the influence of vibration is large, as shown in FIG. Can do. That is, with this configuration, it is possible to approximately satisfy the relationship expressed by the following formula 1.

Note that “approximately satisfying” here means that a structure close to “0” is realized by the configuration of the present invention, and in the present invention, the experimental results shown in FIG. As shown in the figure, it is assumed as an example in which removal of a vibration component of about 20 dB is approximated to “0” in a frequency band where the influence of vibration is practically large, for example, 1 kHz or less.
[Equation 1]
f (0, v) = g (0, v) (1)
This has been found by experiments using many microphones by the present inventor.

  As described above, the first diaphragm 11 is provided with the sound hole 14 in the same manner as a normal microphone, and the incident sound wave enters the inside of the microphone from here and causes the first diaphragm 11 to be displaced. On the other hand, since the second diaphragm 12 is configured to block the incidence of sound waves by a sound insulation barrier or the like, external vibration propagates in the same manner as the first diaphragm 11, but a sound hole is formed in the first diaphragm 11. Sound waves transmitted from the sound are insulated.

With such a configuration, the following relationship of Equation 2 can be approximately realized.
[Equation 2]
g (p, 0) = 0 (2)

In general, in a normal microphone, when the sound pressure p and the vibration v are small, a linear operation is performed, and it is assumed that the relationship of the following equations 3 and 4 is established.
[Equation 3]
f (p, v) = f (p, 0) + f (0, v) (3)
[Equation 4]
g (p, v) = g (p, 0) + g (0, v) (4)

Next, Equations 1 and 2 are substituted into Equation 4 to obtain Equation 5.
[Equation 5]
g (p, v) = g (p, 0) + g (0, v) = 0 + f (0, v) (5)
Here, the difference between the respective conversion results, that is, f (p, v) −g (p, v) is evaluated. The following formula 6 is obtained from the formulas 3, 4, and 5.
[Equation 6]
f (p, v) -g (p, v) = f (p, 0) (6)

  This is an output when only the sound pressure p is extracted and input, and is an ideal aspect to be realized in the present embodiment. Therefore, in the following, based on this theoretical consideration, the signal processing required for practical use is shown (hereinafter referred to as [3. Example of signal processing]), and this embodiment of the present embodiment. The mechanism for realizing the microphone is clearly shown (hereinafter referred to as [4. Specific application example]).

  The first and second diaphragms may have different characteristics as long as they satisfy f (0, v) = g (0, v). F (p, 0) There is no problem even if ≠ g (p, 0) holds. Therefore, in terms of mounting, for example, an expensive microphone is used as the first diaphragm, and an inexpensive microphone (low frequency band having a low frequency band) whose behavior with respect to vibration only as the second diaphragm can be approximated to an expensive microphone as the first diaphragm. It is also possible to use a system such as a main one.

  This is because the present invention pays attention to the characteristic of converting vibration to an electrical signal for the purpose of canceling vibration. In the second diaphragm, g (p, 0 ) = 0, and only g (0, v) is functioning in the second diaphragm, so that it can be grasped by inference. That is, if the first and second diaphragms in the present invention are intentionally defined, it can be said that the conversion characteristics to the electric signal with respect to the change of the diaphragm caused only by the vibration are equal.

  In the principle of the present embodiment as described above, the sound pressure p and the vibration v are input through the sound holes and the structure in the first diaphragm, and only the vibration v through the structure is input in the second diaphragm. By removing the input of only the vibration component v in the second diaphragm from the input of the sound pressure p and the vibration component v in the first diaphragm, the vibration component v in the microphone is removed, Only the sound pressure p can be extracted.

[1-3. Example of signal processing]
First, signal processing required in the present invention can be broadly classified and can be put to practical use in both analog signal processing and digital signal processing. The configuration shown in FIG. 2 realizes Equation 6 as analog signal processing using a differential amplifier circuit.

  On the other hand, the configuration shown in FIG. 3 is realized as adaptive signal processing by ADF (Adaptive Digital Filter), and can be expected to greatly improve characteristics compared to analog processing. The adaptive filter operates so as to approximate the input signal g (p, v) to f (p, v) on the basis of the minimum square error. As a result, a component having a correlation with g (p, v) = g (0, v) (effect due to vibration) in f (p, v) is optimally removed. That is, if the mechanism is such that f (0, v) = g (0, v) is satisfied, other individual differences in sensitivity of the microphone, for example, are automatically absorbed in the adaptive algorithm.

  As the adaptive algorithm, many known algorithms such as the well-known LMS algorithm can be applied. Here, the signal processing block located in the upper part of the adaptive filter shown in FIG. 3 realizes a delay. In the figure, M is a constant generally called a modeling delay, and is set to half the tap length of the adaptive filter.

[1-4. Specific application example]
Next, a specific application example for realizing the present embodiment using the above principle and signal processing will be described.

[1-4-1. Application example to ECM]
(Description of conventional ECM)
First, FIG. 16 shows a general ECM structure as a conventional technique. In general ECM, an exterior (package) 21 is made of a material such as metal, and a sound hole 22 through which a sound wave is incident is provided at the top. In addition, a back plate 24 including a diaphragm 20 made of a fluororesin film or an Si film, and an electret layer 23 made of a polymer film made of a fluororesin or the like, which has been charged in advance by an electret effect by corona discharge, . The ECM forms a capacitor between the diaphragm 20 and the back plate 24 with a spacer 25 interposed therebetween (air gap), and converts the vibration of the diaphragm 20 due to sound waves into a change in capacitance, which is converted into an electric signal. To do.

  The diaphragm 20 and the back plate 24 are fixed to a pedestal 27 provided on the bottom of the ECM by a connection ring 26, and an FET (field effect transistor) provided on the pedestal 27. ) 28 and the connection ring 26 are electrically connected. That is, the ECM results in the diaphragm vibration caused by the sound wave resulting in a change in capacitance and is converted into an electric signal by the FET 28 provided on the pedestal.

(Application example in this embodiment)
Next, the configuration of the microphone 2 of the present embodiment is shown in FIG. As shown in the figure, the microphone structure of the present embodiment having two diaphragms in one ECM of the present embodiment is realized.

  More specifically, the whole is covered with an exterior (package) 21 made of a material such as metal, as in the past, and a sound hole 22 through which an external sound wave is incident is provided on the top. The interior covered with the exterior 21 is provided with an insulator 29, which is a sound insulation member, in the center, and with the insulator 29 as a boundary, chambers A and B are provided at the upper and lower portions, respectively. A and the room B have the following configurations.

  The chamber A above the insulator 29 is provided with a diaphragm 20a made of a fluororesin film or an Si film and an electret layer 23a made of a polymer film made of fluororesin or the like, which is charged in advance by the electret effect by corona discharge. A back plate 24a. In the microphone 2, the spacer 20a is interposed between the diaphragm 20a and the back plate 24a, and a capacitor is formed between them (air gap). The vibration of the diaphragm 20a due to the sound wave is reduced to a change in capacitance, and is converted into an electric signal. The point of conversion is the same as above.

  The lower chamber B of the insulator 29 includes a diaphragm 20b having the same configuration as the upper portion and a back plate 24b including an electret layer 23b. Further, the diaphragm 20b and the back plate 24b are interposed with a spacer 25b, and a capacitor is formed between them (air gap). The vibration of the diaphragm 20b is reduced to a change in capacitance, and converted into an electric signal.

  Further, the microphone 2 in the present embodiment includes pedestals 27a and b at the bottom of each chamber, and the upper structure is fixed to the pedestal 27a. Further, it is electrically connected to an FET (Field Effect Transistor) 28 provided on the pedestal 27b by a connection ring. Further, a differential amplifier D is provided next to the FET 28 on the pedestal 27b, and the differential amplifier D allows f (p, v) input from the diaphragm 20a and the diaphragm 20b to G (p, v), which is an input of, is calculated by the above equation (6).

  In the microphone 2 having the above-described configuration, a device for realizing Equations 1 and 2 that is a basic assumption of the present invention is provided. In other words, two diaphragms are provided in adjacent chambers to approximate the vibration component received by the two diaphragms as much as possible, and the chambers having the two diaphragms are separated by an insulator, which is a sound insulating member, so that sound waves are emitted only to the first chamber. Make it incident. As a result, by removing the input of only the vibration component in the second diaphragm from the input of the sound wave and vibration in the first diaphragm, the vibration component in the microphone can be removed, and clearer sound quality input / output is possible. Become. In addition, it is possible to contribute to the miniaturization of the entire microphone 2 by arranging such components in one housing and configuring as one microphone.

  Furthermore, by adopting a structure in which two diaphragm structures are brought close to each other and stacked in tandem (in series), the influence of only vibration is approximated as much as possible, and Equation 1 is realized. Further, in addition to making the sound insulating material shown as an insulator a sandwich structure, g (p, 0) = 0 in Equation 2 is realized by the merit of using the microphone mechanism itself located at the upper portion as the sound insulating material.

  That is, the first chamber having the two diaphragms and the second chamber are arranged close to each other and arranged in tandem, so that the vibration components in the diaphragm in the first chamber and the diaphragm in the second chamber are reduced. The effect can be approximated as much as possible. Also, the sound insulation material is sandwiched between the first chamber and the second chamber, and the structure of the first chamber itself is a sound insulation material for the second chamber, so that the sound pressure is applied to the diaphragm of the second chamber. Can be prevented from propagating.

  These characteristics due to this structure have been confirmed by experiments to be described later. In addition, by using a common electronic circuit, a more compact structure can be achieved.

  An example for applying the principle of the present invention to the ECM is not limited to the above-described mode, and two independent ECMs having the same characteristics are stacked, and no sound wave enters one microphone. By securing the structure, it can be easily realized if g (p, 0) = 0 expressed by Equation 2 is satisfied.

[1-4-2. Application example to MEMS microphone]
(Description of a general MEMS microphone)
First, FIG. 17 shows a structure of a general MEMS microphone as a conventional technique. In the case of a MEMS microphone, the operating principle of application of a capacitor is the same as in the case of the ECM described above, but since the positive voltage is supplied by the built-in CMOS circuit and operated, there is no charge charge on the back plate. There are features.

  That is, as shown in FIG. 17, the basic structure of the MEMS microphone is a capacitor comprising an electrode plate mounted on a substrate 32 and having two diaphragms 30 and a back plate 31 disposed in close proximity to each other. In addition, a plurality of gap gaps 33 serving as sound holes through which sound waves are incident are provided above the capacitor-type element. A relatively high DC bias voltage is supplied to the capacitor, and a constant charge is charged in a capacitor constituting the MEMS microphone by applying the bias voltage. When the diaphragm 30 vibrates in this state, a high-impedance capacitance change as a capacitor is generated, and this is impedance-converted by the CMOS to obtain a microphone output.

(Application example in this embodiment)
Next, the configuration of the microphone 3 of the present embodiment is shown in FIG. As shown in the figure, the microphone structure of the present embodiment having two diaphragms as a combination of the MEMS microphones of the present embodiment is realized.

  In the microphone 3 in the present embodiment, [2. In the theoretical aspect of vibration removal], it is important to satisfy the equations 1 and 2 shown in the principle of the microphone of the present embodiment. To achieve this, (1) two independent MEMS microphones are stacked. And (2) a method realized as a single MEMS microphone having two diaphragm structures.

  The configuration in which the two MEMS microphones shown in FIG. 5 are stacked has a sound insulation effect by using a capacitor composed of an electrode plate mounted on the substrate 32 shown in FIG. 16 and having two diaphragms 30 and a back plate 31 disposed in close proximity to each other. The insulating substrate 34 (for example, epoxy resin) provided with is interposed, and two are laminated.

  Further, in the configuration in which the two diaphragm structures shown in FIG. 6 are formed as a single MEMS microphone, the substrate is mounted on the substrates 32a and 32b, and consists of an electrode plate in which two diaphragms 30a and a back plate 31b are arranged in close proximity to each other. Capacitors are arranged side by side in the horizontal direction. An insulating substrate 34 is mounted on one diaphragm 30b, and the other is provided with a gap gap 33 serving as a sound hole on the surface as in the conventional case.

  Here, since the MEMS microphone has a fine structure, the spatial positions of the two diaphragms can be brought close to each other. Therefore, approximating Equation 1 is theoretically superior. Therefore, a laminated structure is superior in ECM. However, in a MEMS microphone, there are many advantages of a parallel arrangement configuration as shown in FIG. 6 depending on mounting conditions.

  As described above, in this application example, since the MEMS microphone has a fine structure, the spatial positions of the two diaphragms can be brought close to each other. The vibration component propagating to the first chamber and the second chamber It is easy to approximate the vibration component propagating to. In addition, the MEMS microphone is advantageous even when it is required to be thin as a restriction when mounted on the substrate.

[1-5. Experimental example]
Next, actual measurement results when using the actual signal processing circuit and the microphone 2 shown in FIG. 4 as a configuration example in the ECM in this embodiment are shown, and the principle of the microphone of this embodiment can be actually realized. Indicates that there is. FIG. 7 shows the signal processing circuit used, which specifically implements the analog signal processing shown in FIG.

  In the figure, a good approximation of the desired output f (p, 0) can be obtained in real time simply by connecting the microphone output on the side having the sound hole to MIC1 and connecting the other microphone output to MIC2.

  FIG. 8 compares the presence / absence of the analog circuit in the case where the microphone according to the present embodiment is configured by stacking two ECMs and a larger vibration is applied from the outside. At first glance, it can be seen that vibration component removal of about 20 dB or more is realized in a frequency band of 1 KHz or less, which is greatly affected by vibration. Furthermore, it can be seen from the results of this experiment that a greater attenuation characteristic is realized in a low frequency band (for example, 20 to 30 Hz or less) where the influence of vibration is larger.

  As described above, in the microphone according to the present embodiment, it is possible to input and output a clearer sound quality by removing the vibration component that the microphone collects in principle, and it is possible to dramatically improve the performance of the microphone. Become.

[2. Second Embodiment]
The microphone according to the second embodiment of the present invention is an improvement of the vibration removal performance by improving the structure for backing up the microphone according to the first embodiment.

[2-1. Challenges in parallel configuration]
The following problems exist in the configuration of the microphone in which the two diaphragms shown in the first embodiment are arranged. Here, the problem in the case where two diaphragms are horizontally arranged in parallel will be described. In the case where two diaphragms are horizontally arranged in parallel, between the bases of the two diaphragms as a base for holding them and the diaphragm Physical and geometric relationships are important. This point will be described with reference to FIG.

  In the two diaphragms shown in the first embodiment, there is a difference in sensitivity regardless of whether or not the sound hole of each diaphragm is blocked, but the minute amount generated in the diaphragm as a result due to vibration. The electromotive force generated by the vibration is input information.

  Therefore, unlike sound wave propagation, it is important to fully consider the vibration state as solid wave propagation. FIGS. 9A to 9C show three different states with respect to the relationship between the microphone and the substrate when the MEMS is used as the two diaphragms.

  FIG. 9A conceptually shows a state in which the tire frame exhibits a vibration state that is temporally different. In FIG. 9 (a), the substrate is vibrated although it is slightly vibrated from the outside, and in this case, the two diaphragms arranged at a distance are operated like a both-ends beam holding plate. For this reason, when the microphone having the parallel arrangement shown in the first embodiment is configured as it is, it is necessary to correct the phase shift of the electromotive force caused by the vibration.

  In the case of FIG. 9B, since the two diaphragms are arranged extremely close to each other, it is assumed that the vibration state also shows the same behavior and the phase of the resulting electromotive force also matches. .

  In FIG. 9C, two diaphragms are mounted on a rigid wall. In this case, it is easily guessed that the vibrations of the two diaphragms are affected in exactly the same vibration state as that of the rigid vibration state, and the phase relationship is matched.

  That is, when a microphone is configured by arranging two diaphragms in parallel, it is important to make the two diaphragms as close as possible to each other, and to realize a rigid tight coupling, and practically, The level handles very small vibrations and needs to be constructed very carefully.

  In the description of the second embodiment including FIG. 9, in the drawing, two separate housings (one has a sound hole and the other is shown in FIG. 1B). A chamber is configured with a diaphragm having no sound hole, and each chamber is provided with a diaphragm. However, a single casing as shown in FIG. It can also be realized by a configuration in which the body is separated by a sound insulation member or a configuration using a MEMS microphone as shown in FIGS. 5 and 6, and in the drawings, an image that represents the whole is displayed. . In addition, the microphone having the specific configuration described below as the second embodiment can be realized by ECM as well as the first embodiment, and can also be realized by MEMS.

[2-2. Specific configuration of vibration performance improvement in parallel configuration]
[2-2-1. Mounting on T-shaped member]
(Constitution)
As shown in FIG. 10A, one of the specific configurations for improving the vibration performance shown as the second embodiment uses a member having a T-shaped cross section including a pedestal 41 on which a microphone is placed and a support 42. The microphone 4 is configured by mounting the casings 40 a and 40 b including the two diaphragms 40 c and 40 d on the pedestal 41.

  Specifically, an embodiment in the case where a MEMS microphone provided with a diaphragm is used as the microphone 4 will be described. As shown in FIG. 10, two MEMS microphones, one having a sound hole (commercially available MEMS) and one having a sound hole closed with a resin such as an epoxy resin, are soldered onto a substrate constituting the base 41. The distance between the microphones is set to about 8 mm, for example. A screw is used as the support post 42, and the substrate is joined to the head portion forming the screw dish.

  The microphone 4 is installed on the main body of the microphone or the like at the tip end (lower end in the figure). That is, the contact point with the outside of the microphone 4 is configured to be only the tip of the support column.

(Function and effect)
According to the microphone 4 as described above, the casings 40 a and 40 b provided with the two diaphragms 40 c and 40 d are mounted on the pedestal 41, the pedestal 41 is supported by the support 42, and is physically connected to the outside of the microphone 4. By making the contact point only the tip of the support column 42, all vibration components from the outside with respect to the microphone 4 propagate from the tip of the support column 42. Therefore, the diaphragms 40c and 40d show the same behavior in the vibration state, resulting in the occurrence of the vibration. The power phase is also matched.

  According to such a microphone 4, even in a microphone having a configuration in which two diaphragms are arranged in parallel, an electromotive force phase shift due to vibration does not occur. Therefore, the vibration component in the diaphragm 40c to which the sound pressure and the vibration component are input and the vibration component in the diaphragm 40d to which only the vibration component is input are approximated as much as possible, so that the vibration component can be accurately removed. In addition, it is possible to accurately remove the vibration component that the microphone picks up in principle, and it is possible to provide a microphone that can withstand practical use.

(Experimental result)
Here, the experimental result in the concrete structure aspect of the microphone 4 which consists of the above-mentioned structure is shown. As described above, the MEMS 41 having the diaphragms 40c and 40d is used as the microphone 4, and the pedestal 41 is composed of two MEMS microphones each having a sound hole and one having a sound hole closed with an epoxy resin. Soldering on the substrate, the middle distance between each microphone is about 8 mm. A screw is used as the column 42, and the substrate is joined to the head portion forming the plate of this screw.

  In such a microphone 4, as shown in FIG.10 (b), it installed on the acrylic board A, the acrylic board was vibrated, and the experiment was conducted. A small vibration hammer made of rubber was used as the vibration source.

  First, basic characteristics of signals input to the diaphragm 40c and the diaphragm 40d of the microphone 4 will be described. The microphone 4 receives the signal to the diaphragm 40d as an input, predicts the vibration component, and removes it from the signal of the diaphragm 40c, thereby suppressing the vibration component. For this reason, the sound transmitted through the air is not input to the diaphragm 40c that closes the sound hole, and only vibration is theoretically input. This characteristic was confirmed by the following experiment.

  In the experiment, a sine wave of 1 k [Hz] is reproduced so that the sound pressure in the vicinity of the microphone 4 becomes 90 [dBA], and the time waveform of the input to the microphone 4 in that case is that of the diaphragm 40c in FIG. FIG. 11B shows the diaphragm 40d shown in FIG. 11A, and FIG. 11C shows the frequency characteristics of the diaphragms 40c and 40d.

  In such a state, the vibration position shown in FIG. The time waveform at that time is shown in FIG. 12 (a) for the diaphragm 40c, FIG. 12 (b) for the diaphragm 40d, and the frequency characteristics of the diaphragms 40c, 40d are shown in FIG. 12 (c). As shown in these drawings, it can be confirmed that both sound and vibration are input to the diaphragm 40c, and only vibration is input to the diaphragm 40d.

  From the above results, as shown in FIG. 11, it can be seen that the diaphragm 40d can secure the sound insulation characteristics by closing the sound holes. Further, as described above, the output of the diaphragm 40d that detects only the signal caused by vibration is correlated in the frequency range of the vibration source at least at first glance, in the time domain, and also in the frequency domain. It can be seen that an extremely high output is obtained.

[2-2-2. Vibration reinforcement by ribs]
As shown in FIG. 13, the second specific configuration for improving the vibration performance shown as the second embodiment is a pedestal 51 on which a microphone is placed, and this pedestal is arranged so as to cross or traverse the pedestal. Ribs 52 a and 52 b are provided, and the microphone 5 is configured by mounting the casings 50 a and 50 b including the two diaphragms 50 c and 50 d between the ribs 52 a and 52 b on the pedestal 51.

  The housing 50a has a sound hole and is intended to detect sound waves and vibrations with the diaphragm 50c, whereas the housing 50b seals the sound hole and detects only vibration with the diaphragm 50d. The target point is the same as described above. Further, in the present embodiment, the rib shape is formed with a square cross section, but is not limited to this, and the rib shape may be formed in an L shape, a semicircular shape, a trapezoidal shape, other polygonal shapes, or the like. Can be variously changed from the viewpoint of design and design. Furthermore, the rib includes not only a mode of installing on the pedestal but also a mode in which, for example, a surface on which the casings 50a and 50b are mounted is pulled out from the pedestal, and a remaining raised portion is captured as a rib. Further, the number of ribs is not limited to the provision of two pieces as in the present embodiment, and a single or a plurality of ribs may be provided.

  By providing such ribs 52a and 52b, not only can the vibration suppressing effect on the pedestal 51 be obtained, but also the bending rigidity of the structure can be increased. By increasing the rigidity of the pedestal 51 itself as described above, the vibration of the pedestal 51 can be reduced, and the vibration component propagating from the pedestal 51 to the diaphragms 50c and 50b can be approximated. Thereby, by removing the input of the diaphragm 50d from the input of the diaphragm 50c, it is possible to accurately remove the vibration component, and it is possible to accurately remove the vibration component that the microphone collects in principle. It is possible to provide a tolerable microphone.

[2-2-3. Tight coupling with rigid members]
As shown in FIG. 14, the third specific configuration for improving the vibration performance shown as the second embodiment is a pedestal 61 on which a microphone is placed, and a pedestal made of a material having high rigidity such as carbon nanotubes on the pedestal. 62 is mounted, and the microphone 6 is configured by mounting housings 60 a and 60 b including two diaphragms 60 c and 60 d on the mounting table 62. The housing 60a has sound holes and is intended to detect sound waves and vibrations with the diaphragm 60c, whereas the housing 60b seals the sound holes and detects only vibrations with the diaphragm 60d. The target point is the same as described above.

  Thus, by providing the housings 60 a and 60 b having the two diaphragms 60 c and 60 d on the mounting table 62 made of a rigid material provided on the base 61, the mounting table 62 is also affected by the vibration of the base 61. The vibration component propagating from the pedestal 61 to the diaphragms 60c and 60d can be approximated. Accordingly, by removing the input of the diaphragm 60d from the input of the diaphragm 60c, it is possible to accurately remove the vibration component, and it is possible to accurately remove the vibration component that the microphone picks up in principle. It is possible to provide a tolerable microphone.

[3. Other Embodiments]
The present invention is not limited to the above-described embodiment, and includes, for example, the following aspects. As the second embodiment, the case where two diaphragms are arranged in parallel in the microphone has been taken up, but the first aspect of the specific configuration example is also adopted in the two diaphragm series arrangement shown in the first embodiment. Is possible.

  That is, as shown in FIG. 15, similarly to the above-described embodiment, a member having a T-shaped cross section including a pedestal 71 on which a microphone is placed and a support 72 is used, and two diaphragms 70c and 70d are connected in series to this pedestal 71. The microphone 7 is mounted. At this time, the outer chambers 70a and 70b of the diaphragms 70c and 70d mounted in series are covered with a reinforcing portion 74 made of a rigid material such as a carbon nanotube, or a part thereof is fixed in a reinforcing manner.

  The microphone 7 is installed on the main body of the microphone or the like at the tip (lower end in the figure) of the support column, as shown in the above embodiment. That is, the contact point with the outside of the microphone 7 is configured to be only the tip of the support column.

  According to such a microphone 7, housings 70 a and 70 b having two diaphragms 70 c and 70 d are mounted on the pedestal 71, the pedestal 71 is supported by the support 72, and physical contact with the outside of the microphone 7 is achieved. By making the point only the tip of the column 72, all vibration components from the outside with respect to the microphone 7 propagate from the tip of the column 72. Therefore, the diaphragms 70c and 70d show the same behavior in the vibration state, and the resulting electromotive force This also matches the phase.

  Further, the side surfaces of the exterior chambers 70a and 70b of the diaphragms 70c and 70d arranged in series are reinforced by the reinforcing portion 74 made of a rigid material, so that the diaphragms 70c and 70d are also caused by vibration propagating from the column 72 to the base 71. Vibrate in the same form, and even when the diaphragms are arranged in series, the vibration components propagating to the diaphragms 70c and 70d can be approximated.

  In the microphone 7 as described above, even in a microphone having a configuration in which two diaphragms are arranged in series, a phase shift of electromotive force due to vibration does not occur. Therefore, the vibration component in the diaphragm 70c to which the sound pressure and the vibration component are input and the vibration component in the diaphragm 70d to which only the vibration component is input are approximated as much as possible, so that the vibration component can be accurately removed. In addition, it is possible to accurately remove the vibration component that the microphone picks up in principle, and it is possible to provide a microphone that can withstand practical use.

  Similarly, the second embodiment shows the second and third aspects of the specific configuration example [2-2-2. Vibration reinforcement by ribs] and [2-2-3. The configuration of tight coupling by rigid members] can also be adopted in the two diaphragm series arrangement shown in the first embodiment, and both have the same effects as those shown in the second embodiment. .

1, 2, 3, 4, 5, 6, 7 ... microphone 10 ... casing 11, 12 ... diaphragm 13 ... barrier 14 ... sound hole 20, 20a, 20b ... diaphragm 21 ... exterior 22 ... sound hole 23, 23a, 23b ... Electret layers 24, 24a, 24b ... Back plates 25, 25a, 25b ... Spacers 26 ... Connecting rings 27, 27a, 27b ... Base 28 ... FET
29 ... Insulators 30, 30a, 30b ... Diaphragms 31, 31a, 31b Back plates 32, 32a, 32b ... Substrate 33 ... Gap gap 34 ... Insulating substrates 40a, 40b ... Housings 40c, 40d ... Diaphragm 41 ... Base 42 ... Prop 50a 50b ... casing 50c, 50d ... diaphragm 51 ... pedestal 52a, 52b ... ribs 60a, 60b ... casing 60c, 60d ... diaphragm 61 ... pedestal 62 ... mounting table 70a, 70b ... casing 70c, 70d ... diaphragm 71 ... pedestal 72 ... post 73 ... exterior 74 ... reinforcing part A, B ... chamber D ... differential amplifier circuit

Claims (10)

In a microphone that obtains output by converting the shape change of the diaphragm into a change in capacitance and converting it to an electrical signal.
Two diaphragms are provided,
The two diaphragms are each housed in a separate chamber provided by a member having a sound insulation property, or provided in adjacent chambers separated by a sound insulation member, respectively.
The first chamber provided with the first diaphragm is provided with a sound hole for allowing sound waves to enter,
The second chamber with the second diaphragm is a space where sound waves are blocked,
When the sound pressure for changing the shape of the first diaphragm is p and the vibration is v, the conversion function of the diaphragm to electric vibration is f (p, v),
When the sound pressure for changing the shape of the second diaphragm is p and the vibration is v, the conversion function of the diaphragm to electric vibration is g (p, v).
The first chamber and the second chamber are:
f (0, v) = g (0, v)
And g (p, 0) = 0
Approximately
By approximating f (p, v) from the input signal g (p, v) to f (p, v) by using the adaptive filter,
f (p, v) -g (p, v) = f (p, 0)
A microphone that outputs a sound. A microphone having a capacitor-type element in which a diaphragm and a back plate are arranged opposite each other with a spacer interposed therebetween, and a vibration of the diaphragm is reduced to a change in capacitance and converted into an electric signal to obtain an output. ,
Two capacitor-type elements are provided,
The first and second capacitor-type elements are respectively stored in first and second chambers that are made of a member having a sound insulating property with the same surface directed in the same direction, and are provided separately adjacent to each other, or common. Provided in adjacent first and second chambers separated by a sound insulating member in the package,
Forming a sound hole for capturing sound waves from outside at a position facing the sound wave incident surface of the first capacitor-type element;
Forming a shielding part that shields sound waves from the outside at a position facing the sound wave incident surface of the second capacitor-type element;
When the sound pressure that changes the shape of the diaphragm in the first capacitor-type element is p and the vibration is v, the conversion function of the diaphragm to electric vibration is f (p, v),
When the sound pressure that changes the shape of the diaphragm in the second capacitor-type element is p and the vibration is v, and the conversion function to the electric vibration of the diaphragm is g (p, v),
The first chamber and the second chamber are:
f (0, v) = g (0, v)
And g (p, 0) = 0
Approximately
By approximating f (p, v) from the input signal g (p, v) to f (p, v) by using the adaptive filter,
f (p, v) -g (p, v) = f (p, 0)
A microphone that outputs a sound.   The first diaphragm and the second diaphragm are provided such that a sound wave incident surface faces a direction of a sound wave incident from the sound hole and is arranged in a series direction with respect to the incident direction. The microphone according to claim 1 or 2.   The first capacitor-type element and the second capacitor-type element are provided such that a sound wave incident surface faces a direction of a sound wave incident from the sound hole and is arranged in series with respect to the incident direction. The microphone according to claim 1 or 2, wherein   The said 1st chamber and the said 2nd chamber were provided in parallel with the horizontal direction which is a perpendicular | vertical direction with respect to the direction of the sound wave which injects from the said sound hole. The microphone described.   5. The microphone according to claim 1, wherein each of the first and second capacitor-type elements is a MEMS (Micro Electro Mechanical Systems) element.   The microphone according to any one of claims 1 to 6, wherein the first chamber and the second chamber are closely coupled by a rigid member. The first chamber and the second chamber are mounted on a pedestal and are tightly coupled by a rigid member,
This pedestal is supported by a column,
The microphone according to claim 3 or 4, wherein the support column is installed at an end portion opposite to a side supporting the pedestal. The first chamber and the second chamber are mounted adjacent to a pedestal;
This pedestal is supported by a column,
The microphone according to claim 5, wherein the support column is installed at an end portion opposite to a side supporting the pedestal. The first chamber and the second chamber are mounted on a pedestal;
The microphone according to any one of claims 3 to 5, wherein the pedestal is provided with a rib for suppressing vibration of the pedestal.