CN1630428A - Silicon microphone assembly capable of realizing sound source direction - Google Patents

Abstract

A silicon microphone assembly capable of realizing sound source direction is charactered in that: it contains a hexahedron stent, three heart-shaped directional silicon microphones and a full directional silicon microphone. The said three heart-shaped directional silicon microphones is along the direction perpendicular to the cartesian coordinates whose original point locates in the center of the hexahedron stent, and they are fixed on the front, side and top stent of the hexahedron stent; the full directional silicon microphone is fixed on the bottom stent of the said hexahedron stent stent; and the fifth surface of the hexahedron stent is to install a PCB interface board for the signal output of the micro-silicon microphone assembly, and the last surface is mounted with a dustproof membrane. The said silicon microphone assembly is proved has a very good orientation of the sound source by a simulation test, namely the direction of the sound source is in good agreement with the actual direction, and the higher the sampling frequency of the sound, the better the agreement.

Description

Can realize the silicon microphone assembly of sound source direction

Technical field

The invention belongs to the technical field of silicon micro-microphone.

Background technology

In video conferencing system, video camera is caught spokesman's camera lens and is generally all operated by photographer.Adopt the sound source direction system can improve the automaticity of video conferencing system, greatly reduce cameraman's working strength.The automatic capturing technology of traditional camera lens has infrared tracking, image to follow the tracks of harmony tone lateralization etc.Hong Wang and Peter Chu were at IEEEInternational Conference on Acoustics in 1997, mention in the paper of delivering in the Speech and Signal Processing international conference " Voice source localization for automatic camera pointing system in videoconferencing ", infrared tracking needs the spokesman to carry corresponding infrared transceiver, image is followed the tracks of the object then need manually to preestablish tracking, yet and the sound directional technology is from solution easily.The sound directional technology just began one's study from the 1970s ' age.Traditional sound directional technology generally adopts microphone array, multi-channel data is carried out signal processing methods such as correlation analysis, analysis of spectrum, time-delay analysis.In order to pursue high orientation accuracy, need to adopt high performance microphone and very big microphone array.This makes that whole system is bulky, complicated and costs an arm and a leg.The precision of signal processing algorithm depend on relative position, the ambient noise of microphone consumingly and echo, spectral range of sound source, the number of sound source or the like, see the works Microphone Arrays that Michael Brandstein and Darren Ward published in calendar year 2001, Signal Processing Techniques and Applications.These problems make conventional microphone sound source direction technology be difficult to reduce cost and enter consumer electronics field, thereby limited its extensive use.Along with the development of micro electronmechanical (MEMS) technology, the silicon micro-microphone technology is ripe gradually, and part has begun commercialization.Patrick RichardScheeper, B  rge Nordstrand, Jens Ole Gull  v, Bin Liu, Thomas Clausen, Lise Midjord, the paper that was published on the magazine Journal of Microelectromechanical Systems in 2003 with TorbenStorgaard-Larsen " ANew Measurement Microphone Based on MEMS Technology ", with a day order, Zhang Lintao, Liu Litian, Li Zhijian (Tian-Ling Ren, Lin-Tao Zhang, Li-Tian Liu, Zhi-Jian Li) was published in magazine IEEETransactions on Ultrasonics in 2002, Ferroelectrics, paper on the and Frequency Control " Design Optimizationof Beam-like Ferroelectrics-silicon Microphone and Microspeaker " think, compare with conventional microphone, it is little that silicon micro-microphone has a volume, the precision height, in light weight, encapsulation scheme is flexible, good reproducibility, can manufacture, good anti-vibration, easily and IC integrated, produce advantages such as with low cost in batches.Because the micro-microphone volume is little, the width that a plurality of micro-microphones gather together is still much smaller than the wavelength of audio frequency sound, can regard them as in the sound field a point; The encapsulating structure of micro-microphone can be according to different application requirements specialized designs, and flexibility is bigger, can realize directive property design and many Mikes assembling of device easily; Higher sensitivity guarantees that there are enough signal to noise ratios in system, improves the sound source direction precision.The directive property of utilizing silicon micro-microphone that these advantages propose this paper realizes that sound source direction becomes possibility.

Nineteen eighty-three, reported first is utilized zinc oxide (ZnO) piezoelectric membrane and micro electronmechanical (MEMS) technology in the paper that people such as Royer deliver on magazine Sensors and Actuators A " ZnO on Si IntegratedAcoustic Sensor ", on silicon substrate, produced micro-microphone, the scholars of Holland, the U.S., Germany, Denmark, Switzerland, Singapore and China launch research to this one after another subsequently, and have obtained huge progress.At 2003 beginning of the years, U.S. EMKAY INNOVATIVE PRODUCTS company has released commercialization micro-microphone outturn sample, indicates that this technology begins commercialization.From the angle of input, silicon micro-microphone mainly is divided into piezoelectric type, condenser type, pressure resistance type, modulated Field effect tubular type and light wave conduction etc.The part micro-microphone is operated in the audiorange, and part is used for ultrasonic measurement.

The sensitivity of microphone is called the sensitivity directional property with the characteristic that the sound wave incident direction changes.When micro-microphone is encapsulated into differential structure, i.e. micro-microphone back of the body chamber design has the incident duct, makes sound wave can act on the front and back of vibrating diaphragm simultaneously, and micro-microphone has just had sensitivity directive property.At this moment, when the sound wave incidence angle changes, the sound wave that acts on the vibrating diaphragm front and back is because the propagation path difference, produce certain phase difference after arriving vibrating diaphragm, make and act on changing with incidence angle with joint efforts on the vibrating diaphragm, cause the sensitivity of micro-microphone to change, produced the sensitivity directional property with incidence angle.Fig. 2 is the encapsulating structure of heart-shaped directive property micro-microphone, by the use and the precise design of back side acoustic damping material, the micro-microphone that can realize having particular orientation.

When sound wave during with angle β incident, the ratio of sensitivity is called the sensitivity directivity function when sensitivity of microphone and axially incident (β=0 °), can be described by following formula:

$D\left(\mathrm{\β}\right)=\frac{1+b\cos \left(\mathrm{\β}\right)}{1+b}---\left(1\right)$

In the formula $b=\frac{\mathrm{j\ωd}{Z}_{A0}}{C_0{Z}_A},$ ω is a sound frequency, and d is a microphone back of the body chamber thickness, Z _A0Be microphone back of the body chamber acoustic impedance, Z _ABe the acoustic impedance of microphone back side tone-entering hole, C ₀Be the velocity of sound.When b=0, be circle directive property; During b=1, be heart-shaped directive property; B＞1 o'clock tends to 8 font directive property, i.e. double directing properties.Fig. 2 is the directive property curve of heart-shaped directive property.The direction of microphone directive property numerical value maximum is called main sensitive direction.

For silicon micro-microphone, its size can be accomplished 3mm * 3mm * 0.5mm, even it is littler, compare (as 100 ~ 6000Hz with language frequency range wave length of sound, be that the air medium wavelength is 3440 ~ 57mm), its size is littler one more than the order of magnitude than wave length of sound, can regard the combining structure of several micro-microphones as a point in sound field, sound wave arrives them and produces diffraction, and reflection is ignored.So the variation with frequency in voice band of micro-microphone directive property curve also can be ignored.

Summary of the invention

The object of the present invention is to provide the silicon microphone assembly that to realize sound source direction.

Utilize the directive property of microphone, can realize orientation sound source.Three micro-microphones that will have heart-shaped directive property make three parallel placements of reference axis of its main sensitive direction and vertical coordinate system respectively, as shown in Figure 3.

Suppose that the direction that certain sound wave transmits and the angle of three silicon micro-microphone master sensitive directions are respectively β _x, β _yAnd β _z, then the output voltage of three microphones is respectively:

$V_x=\frac{1+b\cos \left({\mathrm{\β}}_x\right)}{1+b}\mathrm{AP}$

$V_y=\frac{1+b\cos \left({\mathrm{\β}}_y\right)}{1+b}\mathrm{AP}$

$V_z=\frac{1+b\cos \left({\mathrm{\β}}_z\right)}{1+b}\mathrm{AP},---\left(2\right)$

In the formula, P is the sound intensity of sound wave, and A is the sensitivity of silicon micro-microphone.

As can be seen from the above equation, when the micro-microphone characteristic is known, have four unknown numbers, i.e. sound intensity P and directioin parameter β _x, β _yAnd β _zTherefore, separate above-mentioned equation and must introduce an independent equation again.For convenience of calculation, we select a full micro-microphone that points to, and place it in three heart-shaped microphone next doors of pointing to, the absolute sound intensity when its responsive sound wave is arrived at.That is,

V ₀＝AP (3)

By above two formulas, suppose that three micro-microphones all are heart-shaped directive property, b=1 then can obtain the direction vector of sound wave,

In order to improve the precision of sound source direction, the error that does not bring the locus of each micro-microphone of needs compensation on desirable same point.Inconsistent on the space makes the acoustic signals detect that decay on the intensity and the delay on the phase place be arranged.Wherein, airborne sound intensity decay is:

P=P ₀e ^-mxIn the formula, m is attenuation coefficient (m ^-1), x is transmission range (m).

The aerial attenuation coefficient of sound wave is generally less than 0.09.When the air line distance of two microphones is 5mm, get decaying to of the sound intensity by following formula

P≈0.99955P ₀

Therefore, the decay of the sound intensity can be ignored.Comparatively speaking, because the signal errors on the synchronization microphone that phase delay causes is much bigger.Therefore, we reduce this error in the following ways.

The frequency of supposing sampled signal is N times (on the engineering, generally selecting N greater than 10) of acoustic signals frequency.In each sampling time section, the sound source direction system chooses a signal from each microphone.We select the output signal of the maximum of N sampled signal in the sound wave cycle as this microphone.Fig. 4 is sound wave sampling plan diagram.Can regard as equally because arrive sound intensity size on the different microphones, then the output signal error of two microphones only is decided by sample frequency.

If the propagation equation of sound wave is

P＝P ₀sin(2πft) (5)

In the formula: P is the spatial distribution of acoustic pressure, P ₀Be the sound pressure amplitude of sound wave, f is a frequency of sound wave, and t is the time.When sample frequency was Nf, the error of microphone output signal was to the maximum

${\mathrm{dV}}_i=V_i\sin \left(2\mathrm{\πft}\right)-V_i\sin \left(2\mathrm{\πf}(t+\frac{1}{\mathrm{Nf}})\right)$ $t=2\mathrm{k\π}+\frac{\mathrm{\π}}{2}$ The time value, that is:

$\max \left(d{V}_i\right)=(1-\sin (\frac{\mathrm{\π}}{2}+\frac{2\mathrm{\π}}{N}))V_i---\left(6\right)$

In the formula, V _iBe the theoretical output valve of microphone, i=x, y, z.

Then the sound wave direction vector that obtains of Practical Calculation is

Be the convenience of calculation meter, adopt polar coordinates to describe the error of sound wave orientation.If the azimuth of sound wave direction is , the angle of pitch is θ, and then the direction vector of sound wave is

By formula (2), the theoretical output valve of microphone should be:

$V_x=\frac{1+b\cos \mathrm{\φ}\cos \mathrm{\θ}}{1+b}\mathrm{AP}$

$V_y=\frac{1+b\sin \mathrm{\φ}\cos \mathrm{\θ}}{1+b}\mathrm{AP}$

$V_z=\frac{1+b\sin \mathrm{\θ}}{1+b}\mathrm{AP}---\left(9\right)$

By formula (9) substitution formula (6) and (7), can calculate the polar coordinates expression formula of sound wave direction vector test value.According to the trigonometric function relation, can obtain the angle between sound wave direction vector actual value and the test value:

$\mathrm{\&gamma;}=\arccos \left(\frac{{\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="A20041009880300132.png"\; state="\{\{state\}\}">B</figure-callout>}}^2+C^2-{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="A20041009880300132.png"\; state="\{\{state\}\}">A</figure-callout>}}^2}{2\mathrm{BC}}\right)---\left(10\right)$

In the formula:

When Fig. 5 was 30 times of frequency of sound wave for sample frequency, the systematic error that the sound wave direction vector that is calculated by formula (10) calculates was with the relation of sound wave direction.Shown in Figure 5, sample frequency is 30 times of frequency of sound wave, and maximum orientation error is 2.1 °.

Obviously, orientation error and sample frequency have direct relation, and high sample frequency can reduce the system oriented error.Fig. 6 is the relation in system oriented error and sample frequency.Can see that along with the further raising of signal sampling frequency, the maximum orientation error of system is index and reduces.Therefore, the orientation accuracy of this programme is except outside the Pass the precision with micro-microphone itself has, and is relevant with the signal sampling frequency to a greater extent, helps adapting to the application of different orientation accuracies.

The development of micro electronmechanical (MEMS) technology makes existing many devices, system realize miniaturization and microminiaturization, has effectively promoted to use the new product of relevant microdevice, the development of new technology.This paper proposes a kind of sound source direction new solution that adopts the micro-microphone combination, and this scheme has avoided conventional microphone array huge volume, complicated algorithm and fancy price etc. to hinder the factor of its popular application.Theory analysis shows, when the signal sampling frequency was 30 times of sound frequency, the maximum orientation error of system was 2.1 °.And along with the further raising of signal sampling frequency, the maximum orientation error of system is index and reduces, and is applicable to the application of different orientation accuracy requirements.

The invention is characterized in:

1, it contains:

The hexahedron support;

Heart-shaped silicon micro-microphone (X), (Y), (Z) totally three of pointing to, there are signal output part and earth terminal in the back side of each, just, the back of the body two sides tone-entering hole is respectively arranged, their three microphones are positioned at the rectangular axes of above-mentioned hexahedron carriage center respectively along initial point, be fixed on front, side and the end face support of above-mentioned hexahedron support;

The full silicon micro-microphone that points to is fixed on the bottom surface support of above-mentioned hexahedron support, back side audible signal output and ground, and there is a tone-entering hole in the front;

Printed circuit (PCB) interface board, periphery is the public ground pad of above-mentioned four silicon micro-microphones, the centre is four microphone signal o pads that link to each other with the signal output part at the above-mentioned silicon micro-microphone back side respectively, and above-mentioned PCB interface board is fixed on the support of above-mentioned hexahedron support of a side relative with above-mentioned silicon micro-microphone (X);

A dustproof film is fixed on the support with the above-mentioned hexahedron carrier openings side of the relative side of above-mentioned silicon micro-microphone (Y).

Feature of the present invention also is

2, it contains:

The hexahedron support;

Heart-shaped silicon micro-microphone (X), (Y), (Z) totally three of pointing to, there are signal output part and earth terminal in the back side of each, just, respectively there is a tone-entering hole on back of the body two sides;

The full silicon micro-microphone that points to is fixed on the bottom surface support of above-mentioned hexahedron support, back side audible signal output and ground, and there is a tone-entering hole in the front;

" cross " shape flexible PCB plate, four arms turn back and form a cube of opening the one side mouth around it, stick with glue on above-mentioned hexahedron support, the arm of above-mentioned " cross " shape flexible PCB plate from the right side to last, a left side, down, be respectively first, second, article third and fourth, arm, article one four signal ends are arranged on the arm, second, article three, arm and mid portion respectively have a tone-entering hole and silicon micro-microphone signal input part and earth terminal, it is pad, article four, arm has only silicon micro-microphone signal input part and earth terminal, the periphery of above-mentioned " cross " shape flexible PCB plate is public ground, with above-mentioned second, three, article four, the silicon micro-microphone earth terminal of arm and mid portion links to each other, above-mentioned second, three, article four, arm and mid portion are the X that is positioned at the rectangular coordinate system of above-mentioned hexahedron carriage center respectively along initial point, Y, three directions of Z axle are fixed on the corresponding hexahedron support, the above-mentioned heart-shaped silicon micro-microphone (X) that points to, (Y), (Z) be welded in second of " cross " shape flexible PCB plate from the outside with the Reflow Soldering method respectively, article three, on arm and the mid portion; Full sensing silicon micro-microphone also uses the same method and is welded on the 4th arm from the outside, the acoustical signal output at above-mentioned four silicon micro-microphone back sides respectively with second of " cross " shape flexible PCB plate, article three, arm, mid portion links to each other with signal input part on the 4th arm, link to each other with four signal ends on article one arm by the lead-in wire on " cross " shape flexible PCB plate again, the earth terminal at above-mentioned four silicon micro-microphone back sides respectively with second of " cross " shape flexible PCB plate, article three, arm, mid portion links to each other with earth terminal on the 4th arm, is connected to the public ground of flexible PCB plate periphery;

A dustproof film is fixed on the support with the above-mentioned hexahedron carrier openings side of the relative side of above-mentioned silicon micro-microphone (Y).

Experiment showed, that sound bearing and actual sound bearing that computer obtains meet finely, see corresponding diagram.

Description of drawings

Fig. 1 is the heart-shaped encapsulating structure that points to silicon micro-microphone.

1, silicon micro-microphone chip; 2, perforation is gone in the front; 3, acoustic damping material; 4, back surface incident hole; 5, microphone shell; 6 metal lead wires

Fig. 2 is heart-shaped directive property schematic diagram.

Fig. 3 is the stereogram of silicon microphone assembly.

Fig. 4 is the acoustic signals acquisition method.

Fig. 5 is the graph of a relation of sound source direction error and Sounnd source direction.

Fig. 6 is the relation curve of sample frequency and sound source direction error.

Fig. 7 is rectangular coordinate and polar graph of a relation, and is the azimuth, and θ is the angle of pitch.

Fig. 8 is one of structure embodiment of silicon microphone assembly:

7. hexahedron supports among the figure, 8. silicon micro-microphone X, Y, Z are pointed in three hearts, and 9. printed circuit (PCB) interface board 10. points to silicon micro-microphone entirely, 14. dustproof films.

Fig. 9 is the PCB interface board schematic diagram among Fig. 8:

11. public ground pads among the figure, 12. 4 microphone signal pads.

Figure 10 is the heart-shaped back view that points to silicon micro-microphone:

13. signal output parts among the figure, 16. earth terminals, 41. back side tone-entering holes, 2. front tone-entering hole

Figure 11 is the heart-shaped front elevation that points to silicon micro-microphone

Figure 12 is the full back view that points to silicon micro-microphone

Figure 13 is the full front elevation that points to silicon micro-microphone

Figure 14 be silicon microphone assembly structure embodiment two:

15. flexible PCB interface boards among the figure, 14. dustproof films.

Figure 15 is a flexible PCB interface board schematic diagram,

42. tone-entering holes among the figure.

Figure 16 is an emulation testing curve (): experiment condition is the fixing angle of pitch, the change azimuth, and signal frequency is 1k, sample frequency is 30k

A. the angle of pitch is 0 °; B. the angle of pitch is 45 °; C. the angle of pitch is 60 °.

Figure 17 is an emulation testing curve (two): experiment condition is the constant bearing angle, changes the angle of pitch, and signal frequency is 1k, and sample frequency is 30k

A. the azimuth is 0 °; B. the azimuth is 45 °; C. the azimuth is 60 °; D. the azimuth is 90 °; E. the azimuth is 180 °.

Embodiment is seen Fig. 8 ~ 15.

According to the requirement of algorithm, four silicon micro-microphones are separately fixed on four faces of a hexahedron support, and wherein three heart-shaped silicon micro-microphones that point to are respectively perpendicular to three reference axis of rectangular coordinate system.

In first embodiment shown in Figure 8, in order to determine the mutual locus of silicon micro-microphone (8X, 8Y, 8Z, 10), silicon micro-microphone (8X, 8Y, 8Z, 10) is fixed on glue on four faces of a hexahedron support (7), and the front of silicon micro-microphone (8X, 8Y, 8Z, 10) outwardly.Fix a PCB interface board (9) with glue on the 5th face.Around the PCB interface board the public ground of silicon micro-microphone (8X, 8Y, 8Z, 10), four middle signal pads connect the signal output part of four silicon micro-microphones (8X, 8Y, 8Z, 10) respectively with lead, make this PCB interface board (9) of signal output all passing through of whole assembly.The heart-shaped front and back structure of pointing to silicon micro-microphone (8X, 8Y, 8Z) and full sensing silicon micro-microphone (10) is seen diagram.All there are two pads at their back side, is respectively earth terminal and signal end.Heart-shaped silicon micro-microphone (8X, 8Y, the 8Z) back side of pointing to also has a tone-entering hole, does not have and point to silicon micro-microphone (10) entirely.The 6th face of hexahedron support (7) covers a dustproof film (14).

In second embodiment shown in Figure 14, the main common PCB interface board (9) that adopts in the last scheme of flexible PCB interface board (15) replacement, the wiring of design is all linked the output of flexible PCB circuit board (15) with the signal of four silicon micro-microphones (8X, 8Y, 8Z, 10) in advance simultaneously, promptly on article one arm of flexible PCB interface board (15).In the flexible PCB interface board (15), the design of circuit pad is corresponding with the back side pad of silicon micro-microphone (8X, 8Y, 8Z, 10), points to the middle tone-entering hole that has of three corresponding parts of silicon micro-microphone (8X, 8Y, 8Z) with heart.During assembling, earlier with four silicon micro-microphones (8X, 8Y, 8Z, 10) according to the relevant position, be welded on the flexible PCB interface board (15) with the Reflow Soldering method, again four parts around the flexible PCB interface board (15) are turned back and form a hexahedron of opening the one side mouth, this hexahedron is sticked with glue on hexahedron support (7), make each silicon micro-microphone (8X, 8Y, 8Z, 10) keep certain relative tertiary location.Equally, at the sticking dustproof film (14) of the one side of hexahedron support (7) and flexible PCB interface board (15) cube opening.The signal of silicon microphone assembly is by the output output of flexible PCB interface board (15).

Claims (2)

1. can realize the silicon microphone assembly of sound source direction, it is characterized in that it contains:

The hexahedron support;

Heart-shaped silicon micro-microphone (X), (Y), (Z) totally three of pointing to, there are signal output part and earth terminal in the back side of each, just, the back of the body two sides tone-entering hole is respectively arranged, their three microphones are fixed on front, side and the end face support of above-mentioned hexahedron support respectively along the direction that is positioned at the rectangular axes of above-mentioned hexahedron carriage center perpendicular to initial point;

The full silicon micro-microphone that points to is fixed on the bottom surface support of above-mentioned hexahedron support, back side audible signal output and ground, and there is a tone-entering hole in the front;

Printed circuit (PCB) interface board, periphery is the public ground pad of above-mentioned four silicon micro-microphones, the centre is four microphone signal o pads that link to each other with the signal output part at the above-mentioned silicon micro-microphone back side respectively, and above-mentioned PCB interface board is fixed on the support of above-mentioned hexahedron support of a side relative with above-mentioned silicon micro-microphone (X);

A dustproof film is fixed on the support with the above-mentioned hexahedron carrier openings side of the relative side of above-mentioned silicon micro-microphone (Y).

2, can realize the silicon microphone assembly of sound source direction, it is characterized in that it contains:

The hexahedron support;

Heart-shaped silicon micro-microphone (X), (Y), (Z) totally three of pointing to, there are signal output part and earth terminal in the back side of each, just, respectively there is a tone-entering hole on back of the body two sides;

The full silicon micro-microphone that points to is fixed on the bottom surface support of above-mentioned hexahedron support, back side audible signal output and ground, and there is a tone-entering hole in the front;

" cross " shape flexible PCB interface board, four arms turn back and form a cube of opening the one side mouth around it, stick with glue on above-mentioned hexahedron support, the arm of above-mentioned " cross " shape flexible PCB interface board from the right side to last, a left side, down, be respectively first, second, article third and fourth, arm, article one four signal ends are arranged on the arm, second, article three, arm and mid portion respectively have a tone-entering hole and silicon micro-microphone signal input part and earth terminal, it is pad, article four, arm has only silicon micro-microphone signal input part and earth terminal, the periphery of above-mentioned " cross " shape flexible PCB interface board is public ground, with above-mentioned second, three, article four, the silicon micro-microphone earth terminal of arm and mid portion links to each other, above-mentioned each bar arm and mid portion are along the X that is positioned at the rectangular coordinate system of above-mentioned hexahedron carriage center perpendicular to initial point, Y, the direction of Z axle, be fixed on the corresponding hexahedron support the above-mentioned heart-shaped silicon micro-microphone (X) that points to, (Y), (Z) be welded in second of " cross " shape flexible PCB interface board from the outside with the Reflow Soldering method respectively, article three, on arm and the mid portion; Full sensing silicon micro-microphone also uses the same method and is welded on the 4th arm from the outside, the acoustical signal output at above-mentioned four silicon micro-microphone back sides respectively with second of " cross " shape flexible PCB plate, article three, arm, mid portion links to each other with signal input part on the 4th arm, link to each other with four signal ends on article one arm by the lead-in wire on " cross " shape flexible PCB interface board again, the earth terminal at above-mentioned four silicon micro-microphone back sides respectively with second of " cross " shape flexible PCB interface board, article three, arm, mid portion links to each other with earth terminal on the 4th arm, is connected to the public ground of flexible PCB plate periphery;

A dustproof film is fixed on the support with the above-mentioned hexahedron carrier openings side of the relative side of above-mentioned silicon micro-microphone (Y).

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