CN101986723B - Test system and test method for pressure gradient microphone - Google Patents

Abstract

The invention provides a test system for a pressure gradient microphone, which comprises a sound source, a monitoring microphone separated from the sound source by a certain distance and the pressure gradient microphone to be tested, wherein the test system for the pressure gradient microphone further comprises a travelling wave tube with smooth inner wall, one end of the travelling wave tube is in butt joint with the sound source, an acoustic wedge is arranged at the other end, a sound-absorbing material is arranged in the acoustic wedge, the monitoring microphone and the pressure gradient microphone to be tested are inserted into the travelling wave tube, and sound pressure emitted by the sound source reaches the monitoring microphone and the pressure gradient microphone to be tested through the travelling wave tube. The test system for the pressure gradient microphone can be used for large-batch testing on a production line and realize high testing precision.

Description

Differential pressure microphone test system and test method

【Technical field】

The invention relates to a test system and a test method for a pressure difference microphone, in particular to a traveling wave tube test system and a test method for testing a pressure difference microphone.

【Background technique】

Mobile communication technology has developed rapidly in recent years. Consumers are using mobile communication devices more and more, and their requirements for mobile communication devices are not only to be able to make calls, but also to be able to provide high-quality call effects. Especially with the development of mobile multimedia technology, the call quality of mobile phones is even more important. As one of the transducers of a mobile phone, the performance of the differential pressure microphone directly affects the call quality. Therefore, it is very important to test the performance of the differential pressure microphone before using it.

The principle of the differential pressure microphone test is to make the two sides of the diaphragm of the differential pressure microphone receive sound, so that the differential pressure microphone responds to the pressure difference. The relevant differential pressure microphone test system tests the differential pressure microphone in a free field in an anechoic chamber, and it must be ensured that a certain test distance is set during the test, and the test distance is greater than 1m. However, this test system is not suitable for mass testing on the production line.

Therefore, it is necessary to provide a new differential pressure microphone testing system to solve the above problems.

【Content of invention】

The technical problem to be solved by the present invention is to provide a differential pressure microphone testing system that is suitable for mass testing on production lines and has high testing accuracy.

According to the above technical problems, a differential pressure microphone test system has been designed, the purpose of which is to achieve: a differential pressure microphone test system, including a sound source and a monitoring microphone at a certain distance from the sound source and the pressure to be measured Poor microphone. Wherein, the differential pressure microphone test system also includes a traveling wave tube with a smooth inner wall, one end of the traveling wave tube is connected to the sound source, and the other end is provided with a sound-absorbing wedge, and a sound-absorbing wedge is provided inside the sound-absorbing wedge. Material. The monitoring microphone and the pressure difference microphone to be measured are inserted into the traveling wave tube, and the sound pressure emitted by the sound source reaches the monitoring microphone and the pressure difference microphone to be measured through the traveling wave tube.

Preferably, the traveling wave tube is provided with a tube wall, and the tube wall is provided with a plurality of test holes penetrating the tube wall, and the monitoring microphone and the pressure difference microphone to be measured are inserted into the test holes through the test holes. inside the traveling wave tube.

Preferably, the traveling wave tube is made of plexiglass material, and its cross section is square.

Preferably, the distance between the monitoring microphone and the sound-absorbing wedge is one length of the sound-absorbing wedge.

Preferably, the sound source is a full-band speaker, and the monitoring microphone is a pressure-type standard 1/2-inch microphone.

Preferably, the differential pressure microphone test system is also provided with a coupling cavity, the traveling wave tube is connected to the sound source by connecting the coupling cavity, and the cross-sectional shape of the end of the coupling cavity that is connected to the sound source is The shape of the sound source is consistent with that of the traveling wave tube, and the cross-sectional shape of the end connected to the traveling wave tube is consistent with the shape of the traveling wave tube.

Preferably, the test holes include a plurality of first test holes for testing the differential pressure microphone to be tested and a second test hole not on the same plane as the first test hole, and the monitoring microphone is controlled by the second test hole inserted into the traveling wave tube.

Preferably, the first test holes are in the shape of a truncated cone, and there are three of them spaced equidistantly.

The present invention also provides a test method based on the above-mentioned differential pressure microphone test system, characterized in that: the method comprises the following steps:

providing a sound source, said sound source being a full-range speaker;

providing a monitoring microphone at a distance from the sound source;

A traveling wave tube is provided, one end of which is connected to the sound source, and the other end is provided with a sound-absorbing wedge, and a sound-absorbing material is provided inside the sound-absorbing wedge, and the traveling wave tube is provided with a plurality of first test holes and the The first test hole is not in the second test hole of the same plane, and the first test hole includes the first test hole A, the first test hole B and the first test hole C;

Provide several differential pressure microphones to be tested;

An audio analyzer is provided, which is respectively connected to the sound source, the monitoring microphone and the differential pressure microphone to be measured;

Insert the monitoring microphone and the differential pressure microphone to be tested into the wave tube through the second test hole and the first test hole A respectively, and insert the first test hole B and the first test hole B that are not inserted into the microphone to be tested The first test hole C is sealed, and then the sound pressure emitted by the sound source passes through the traveling wave tube to the monitoring microphone and the pressure difference microphone to be measured, and the test result is analyzed by an audio analyzer;

In the same way, change the pressure difference microphone to be tested to the first test hole B or the first test hole C for testing, analyze and compare the test results, and determine the position where the test value of the pressure difference microphone to be tested is closest to the required theoretical value is the best test location.

Preferably, the pressure difference microphone to be measured is tooled so that the upper part is a cylindrical rod, the middle part is a conical plug matching the first test hole, and the lower part is a thin rod to fix the pressure difference to be measured microphone.

Compared with the related art, the differential pressure microphone testing system of the present invention can be used for mass testing on the production line and has high testing accuracy.

【Description of drawings】

FIG. 1 is a three-dimensional structure diagram of a differential pressure microphone testing system of the present invention.

Fig. 2 is a partial sectional view along line A-A in Fig. 1 .

Fig. 3 is a structural diagram of the differential pressure microphone testing system of the present invention, which has been connected with an audio analyzer.

Fig. 4 is a structural diagram of the tooling of the pressure difference microphone to be tested in the present invention.

【Detailed ways】

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in FIGS. 1-3 , a differential pressure microphone testing system 1 includes a sound source 5 , a monitoring microphone 6 and a differential pressure microphone 7 to be tested, which are separated from the sound source 5 by a certain distance. Among them, the differential pressure microphone test system 1 also includes a traveling wave tube 3 with a smooth inner wall, one end of the traveling wave tube 3 is connected to the sound source 5 , and the other end is provided with a conical sound-absorbing wedge 2 . The length of the sound-absorbing wedge 2 is determined by the low-frequency cut-off frequency of the sound wave. Sound-absorbing wedge 2 is provided with sound-absorbing material. The monitoring microphone 6 and the differential pressure microphone 7 to be measured are inserted into the traveling wave tube 3 , and the sound pressure emitted by the sound source 5 reaches the monitoring microphone 6 and the differential pressure microphone 7 to be measured through the traveling wave tube 3 .

In this embodiment, the traveling wave tube 3 is provided with a tube wall 33, and the tube wall 33 is provided with a number of test holes (not labeled) passing through the tube wall 33, and the monitoring microphone 6 and the pressure difference microphone 7 to be tested are inserted into the row through the test holes Inside wave tube 3. Specifically, the test holes include several first test holes 31 for testing the differential pressure microphone 7 to be tested and a second test hole 32 not on the same plane as the first test hole 31, and the differential pressure microphone 7 to be tested is formed by the first test hole 31 is inserted into the traveling wave tube 3 , and the monitoring microphone 6 is inserted into the traveling wave tube 3 through the second testing hole 32 . Preferably, there are three first test holes 31 equidistantly spaced apart, and their shape is in the shape of a truncated cone. Such an arrangement will have a better test and comparison effect. Of course, other numbers of the first test holes can also be set, and the distances between them do not have to be equidistant. In the present invention, the so-called truncated cone shape refers to removing the tip on the basis of the cone, so that the area of the upper surface is smaller than the area of the lower surface.

The reason for the smooth inner wall of the traveling wave tube 3 is to prevent the viscous damping of the tube wall 33 from attenuating the sound wave, thereby reducing test errors. In order to facilitate the manufacture and processing of the traveling wave tube 3 , the traveling wave tube 3 is made of a plexiglass material to make a plexiglass tube with a square cross section. Of course, the traveling wave tube can also be made of other materials, and its cross section can also be rectangular, circular or other shapes, which are all feasible.

Specifically, this embodiment is described by taking the test frequency range of 200 Hz-5000 Hz as an example. In fact, this is only the normal working frequency range of the pressure difference microphone, and it is also feasible to exceed this frequency range. The tube wall 33 of the traveling wave tube 3 has a certain thickness, the purpose of which is to better ensure the sound insulation effect of the traveling wave tube 3 and prevent external noise interference. In comprehensive consideration of factors such as sound insulation effect and processing cost, the thickness of the traveling wave tube 3 is set to 1 cm, and other thicknesses are also possible.

In order to test the required conditions, the sound wave in the traveling wave tube 3 is designed as a plane wave, which can be approximated as placing the microphone to be tested in an infinite free field, which can meet the required test conditions. In the traveling wave tube 3 , besides plane waves, there may also be higher-order mode waves. There is a normal mode corresponding to a pair of subscript values (m, n), which is called the (m, n)th normal mode. High-order waves exist only when f>f _mn , where f is the frequency of the sound wave, and f _mn is called the normal frequency of the (m, n)th mode:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; mn</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\sqrt{{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; m</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; no</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Wherein, c ₀ is the speed of sound, and l _x , ly _y are the length and width of the section of the traveling wave tube 3 , respectively. In order to ensure that there are only plane waves and no higher-order mode waves in the traveling wave tube 3, the frequency of the sound wave must be smaller than the cut-off frequency of the tube, namely:

$\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 00</span>}}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; xy</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, f ₀₀ is the plane wave frequency, f is the sound wave frequency, and l _xy is the inner diameter of the traveling wave tube. Because the cross section is a square traveling wave tube, then l _x = _ly =l _xy , so when the formula (2) is satisfied, only f ₀₀ frequency waves exist, that is, plane waves.

The high-frequency critical value of the sound wave mainly determines the thickness of the traveling wave tube. The higher the value, the thinner the tube, the greater the attenuation of the tube wall, and the greater the processing difficulty. When fh=5kHz, l _x = _ly =l _xy , combined with formulas (1) and (2), it can be obtained that l _xy <0.0343m, that is, the inner diameter of the traveling wave tube 3 must be less than 3.43cm. In fact, if the high-frequency critical value is different, the resulting l _xy value is also different, but the principle is the same.

Therefore, based on the calculation of the test frequency range, the inner diameter of the traveling wave tube 3 is set to 3 cm in this embodiment. In fact, it is feasible to meet the requirement that the inner diameter of the traveling wave tube is less than 3.43 cm. When the inner diameter of the traveling wave tube 3 is set to 3 cm, the sound wave frequency is less than the cut-off frequency of the traveling wave tube 3, which can ensure that there are only plane waves in the traveling wave tube 3 and no high-order harmonics, thereby increasing the accuracy of the test.

The sound source 5 selects a full-band loudspeaker with a straight frequency response curve and little distortion. Because the full-band speaker can easily provide a sound field with a sound pressure level fluctuation of less than 0.2dB and a distortion of less than 1%, the test accuracy in such a sound field is higher. Moreover, the full-band speakers in different frequency bands can also easily provide a sound field that meets the required frequency. Of course, other loudspeakers or microphones can also be used for the sound source 5 . The monitoring microphone 6 is a pressure-type standard 1/2-inch microphone, which is used to monitor the sound pressure level and total harmonic distortion rate of the sound source 5 and calibrate the sound field of the sound source 5 . In fact, using the standard microphone as the monitoring microphone 6 is to better improve the test accuracy, and its size is set according to the specific example of this embodiment. The principle is the same in other embodiments, and its size is not necessarily 1/2 inch.

λ是声波波长，

故可得出l_a＝0.43m。为了减少临界值处的测试误差，本实施方式中设置的吸声尖劈2长度为50cm。当然，并非其长度一定设为50cm。The low-frequency critical value of the sound wave mainly determines the length of the sound-absorbing wedge 2 . When the low frequency fl=200Hz, the length of sound-absorbing wedge 2

λ is the acoustic wavelength,

Therefore, it can be obtained that l _a =0.43m. In order to reduce the test error at the critical value, the length of the sound-absorbing wedge 2 set in this embodiment is 50 cm. Of course, the length is not necessarily set to 50 cm.

The sound-absorbing wedge 2 cannot absorb sound waves 100%, and there must be a reflection of the sound waves at its front end. The reflected waves will interfere with the sound waves of the sound source 5 so that the sound field is uneven, and the feedback of the monitoring microphone 6 to the sound field is inaccurate. Therefore, the distance between the monitoring microphone 6 and the sound-absorbing wedge 2 is one length of the sound-absorbing wedge 2, so that the influence of reflected waves on the sound field can be reduced.

Due to the near-field effect of the pressure difference microphone 7 to be tested, its sensitivity changes with the distance, thus causing test errors. The test error caused by the near-field effect should be minimized. The distance between the sound source and the microphone to be tested needs to be set as the far-field range. The far-field condition is k·r>>1, where k is the wave number, r is the axial distance between the pressure difference microphone 7 to be tested and the sound source 5 , and r>>0.27m is calculated according to this far-field condition. In this embodiment, r is set to 40cm, which is only a randomly set distance after the conditions are met. Specifically, the distance between the first test hole B 31b and the pressure difference microphone 7 to be tested is 40cm.

In addition, in this embodiment, a first test hole A 31a and a first test hole C 31c are respectively opened on both sides of the first test hole B 31b. In this way, the test results can be compared under the same conditions to further reduce the test error. Of course, more first test holes 31 can also be provided. Preferably, the first test hole A 31a, the first test hole B 31b and the first test hole C 31c are equidistantly spaced apart by 20cm.

Due to the arrangement of components such as the sound-absorbing wedge 2 and the first test hole 31 , specifically, the arrangement length of the traveling wave tube 3 is not less than 140 cm. Of course, the sound-absorbing wedge 2, the first test hole 31 and other components are set differently, and the length of the traveling wave tube is also changed, but the principle is the same.

The differential pressure microphone test system 1 is also provided with a coupling cavity 4, the traveling wave tube 3 is docked with the sound source 5 by connecting the coupling cavity 4, and the cross-sectional shape of the end of the coupling cavity 4 docked with the sound source 5 is consistent with the shape of the sound source 5. The cross-sectional shape of the end connected to the traveling wave tube 3 is consistent with the shape of the traveling wave tube 3 . For example, in this embodiment, the sound source 5 is a rectangular full-band loudspeaker, and the traveling wave tube 3 has a square cross-section. The end of the coupling cavity 4 connected to the sound source 5 has a rectangular cross-section, and the end connected to the traveling wave tube 3 Its cross section is square. The cross-section of the coupling cavity 4 changes continuously, gradually transitioning from a rectangle to a square, which can reduce wall reflection during sound wave propagation, maximize the sound energy transmission coefficient, and improve test accuracy.

As shown in Figure 2-3, the present invention also provides a test method based on the above-mentioned differential pressure microphone test system 1, which is characterized in that: the method includes the following steps:

A sound source 5 is provided, and the sound source 5 is a full-band speaker;

Provide a monitoring microphone 6, which is separated from the sound source 5 by a certain distance;

A traveling wave tube 3 is provided, one end of which is connected to the sound source 5, and the other end is provided with a sound-absorbing wedge 2, and a sound-absorbing material is arranged inside the sound-absorbing wedge 2, and a plurality of first test holes 31 and the first testing hole 31 are arranged on the traveling wave tube 3. The test hole 31 is not in the same plane as the second test hole 32 . The first test hole 31 includes a first test hole A 31a, a first test hole B 31b, and a first test hole C 31c.

Provide several differential pressure microphones 7 to be tested;

An audio analyzer 8 is provided, which is respectively connected to the sound source 5, the monitoring microphone 6 and the differential pressure microphone 7 to be measured;

Insert the monitoring microphone 6 and the well-equipped differential pressure microphone 7 into the traveling wave tube 3 through the second test hole 32 and the first test hole A 31a respectively, and insert the first test hole B 31b that is not inserted into the microphone 7 to be tested. Seal with the first test hole C 31c. Then the sound pressure from the sound source 5 passes through the traveling wave tube 3 to the monitoring microphone 6 and the pressure difference microphone 7 to be tested, and the test result is analyzed by the audio analyzer 8 . In the same way, change the pressure difference microphone 7 to be tested to the first test hole B 31b or the first test hole C 31c for testing, analyze and compare the test results, and use the test value of the pressure difference microphone 7 to be the closest to the required theoretical value. The location is determined as the optimal test location.

In order to test more conveniently and test accuracy is higher, as shown in Figure 4, the pressure difference microphone 7 to be tested is carried out tooling, and the diameter is set on the upper part of the tooling to be a cylindrical rod 71 of 1/2 inch, certainly, its size and shape can be Set differently as needed. The middle part is a conical plug 72 matched with the first test hole 31, and the sealing effect of the plug with this structure is better. The lower part is a thin rod 73 to fix the differential pressure microphone 7 to be measured. Specifically, the tooled pressure difference microphone 7 to be measured is inserted into the traveling wave tube 3 so that it is located in the center of the traveling wave tube 3 and the diaphragm (not shown) of the pressure difference microphone 7 to be measured is in contact with the traveling wave tube 3. The axis of the tube 3 is vertical, which can ensure that the sound wave acts on the diaphragm of the microphone 7 to be tested at an incident angle of 0 degrees, reducing the test distortion.

Compared with related technologies, the differential pressure microphone testing system of the present invention is convenient to use due to its small size and does not need to be used in an anechoic chamber, and can be used for mass testing on production lines with high testing accuracy.

What has been described above is only the embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, improvements can be made without departing from the creative concept of the present invention, but these all belong to the present invention. scope of protection.

Claims (9)

1. A differential pressure microphone test system, comprising a sound source and a monitoring microphone and a differential pressure microphone to be measured at a certain distance from the sound source, and a device connected to the sound source, the monitoring microphone and the differential pressure microphone to be measured The audio analyzer for analyzing test results is characterized in that: the differential pressure microphone test system also includes a traveling wave tube with a smooth inner wall, one end of the traveling wave tube is connected to the sound source, and the other end is provided with a sound-absorbing wedge , the sound-absorbing wedge is provided with a sound-absorbing material, the monitoring microphone and the pressure difference microphone to be measured are inserted into the traveling wave tube, and the traveling wave tube is provided with a number of first test holes and the first test hole The second test hole that is not on the same plane, the first test hole includes the first test hole A, the first test hole B and the first test hole C, and the monitoring microphone and the pressure difference microphone to be tested are respectively controlled by the second test hole A, the first test hole B and the first test hole C. The test hole and the first test hole A are inserted into the wave tube, the first test hole B and the first test hole C that are not inserted into the microphone to be tested are sealed, and the sound pressure emitted by the sound source passes through the traveling wave The tube reaches the monitoring microphone and the pressure difference microphone to be tested, and the test result is analyzed by an audio analyzer. Similarly, the pressure difference microphone to be tested is switched to the first test hole B or the first test hole C for testing. Compare the test results, and determine the optimal test position where the test value of the pressure difference microphone to be tested is closest to the required theoretical value. the 2 . The differential pressure microphone testing system according to claim 1 , wherein the traveling wave tube is provided with a tube wall, and the first and second test holes penetrate the tube wall. 3 . the 3. The differential pressure microphone testing system according to claim 2, wherein the traveling wave tube is made of plexiglass material, and its cross section is square. the 4 . The differential pressure microphone testing system according to claim 3 , wherein the distance between the monitoring microphone and the sound-absorbing wedge is one length of the sound-absorbing wedge. the 5. The differential pressure microphone testing system according to claim 4, wherein the sound source is a full-band speaker, and the monitoring microphone is a pressure-type standard 1/2-inch microphone. the 6. The differential pressure microphone test system according to claim 5, characterized in that: the differential pressure microphone test system is also provided with a coupling cavity, and the traveling wave tube is connected to the sound source by connecting the coupling cavity The cross-sectional shape of the end of the coupling cavity connected to the sound source is consistent with the shape of the sound source, and the cross-sectional shape of the end connected with the traveling wave tube is consistent with the shape of the traveling wave tube. the 7. The differential pressure microphone testing system according to claim 6, characterized in that: the first testing holes are in the shape of a circular frustum, and there are three of them spaced equidistantly. the 8. A method for testing a differential pressure microphone, characterized in that: the method may further comprise the steps: Provide a sound source, the sound source is a full-range speaker; providing a monitoring microphone, which is separated from the sound source by a certain distance; A traveling wave tube is provided, one end of which is connected to the sound source, and the other end is provided with a sound-absorbing wedge, and a sound-absorbing material is provided inside the sound-absorbing wedge, and the traveling wave tube is provided with a plurality of first test holes and the The first test hole is not in the second test hole of the same plane, the first test hole includes the first test hole A, the first test hole B and the first test hole C; Provide several differential pressure microphones to be tested; An audio analyzer is provided, which is respectively connected to the sound source, the monitoring microphone and the differential pressure microphone to be measured; Insert the monitoring microphone and the differential pressure microphone to be tested into the wave tube through the second test hole and the first test hole A respectively, and insert the first test hole B and the first test hole B that are not inserted into the microphone to be tested The first test hole C is sealed, and then the sound pressure emitted by the sound source passes through the traveling wave tube to the monitoring microphone and the pressure difference microphone to be tested, and the test result is analyzed by an audio analyzer; In the same way, change the pressure difference microphone to be tested to the first test hole B or the first test hole C for testing, analyze and compare the test results, and determine the position where the test value of the pressure difference microphone to be tested is closest to the required theoretical value is the best test location. the 9. The method for testing a differential pressure microphone according to claim 8, wherein: the differential pressure microphone to be tested is tooled so that its upper part is set as a cylindrical rod, and the middle part is for matching with the first test hole. Conical plug, the lower part is a thin rod to fix the pressure difference microphone to be measured. the

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