Device and method for testing and adjusting sensitivity of microphone

Abstract

The invention discloses a microphone sensitivity test adjusting device and method, and the method comprises the following steps: S01, placing a reference microphone on the device, and outputting a sinusoidal signal A with a fixed frequency and amplitude to a metal diaphragm and a rear polar plate through a signal generator, so that the metal diaphragm generates vibration; s02, measuring the displacement amplitude of the metal diaphragm in the step S01 by using a Doppler vibration meter, and recording the displacement amplitude as X; s03, taking off the reference microphone and replacing the reference microphone with a microphone to be adjusted; s04, outputting a sinusoidal signal A with fixed frequency and amplitude to the microphone to be adjusted by using a signal generator to enable a metal diaphragm to vibrate; s05, measuring the displacement amplitude of the metal diaphragm in the step S04 by using a Doppler vibration meter, and recording the displacement amplitude as Y; s06, comparing the difference between X and Y, and adjusting the tension of the metal diaphragm of the microphone to be adjusted; and S07, repeating the steps S05 to S06 until the sensitivity of the microphone is adjusted to be consistent with that of the reference microphone. According to the invention, the technical problem that the test result of the existing microphone sensitivity test adjusting method has large errors can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of microphones, and in particular to a microphone sensitivity testing and adjusting device and method. Background Art

[0002] The condenser microphone is composed of parallel back plates and a stretched metal diaphragm. The back plates and the diaphragm are electrically insulated from each other, forming two electrodes of a capacitor with air as the medium. Then, a certain charge is applied to the capacitor by increasing the polarization voltage between the two electrodes or coating the back plates with a layer of electret material and polarizing them. Therefore, for a microphone in production, its sensitivity is adjusted mainly by changing the tension of the metal diaphragm when the distance area between the two electrodes, the amount of charge and the structure are determined.

[0003] like Figure 1 As shown, the sensitivity adjustment of microphones in the existing production process is usually to apply a variable electric field force to the metal diaphragm on the microphone through an electrostatic actuator to make the diaphragm vibrate at a certain frequency and amplitude. The amplitude of the microphone vibration will be equivalent to the amplitude generated by a certain sound pressure. At this time, the value obtained by dividing the output voltage amplitude of the detection microphone by the equivalent sound pressure is the sensitivity of the microphone. The tension of the metal diaphragm on the capacitor microphone is adjusted according to the difference between the sensitivity obtained by this test and the reference sensitivity of the microphone, and the sensitivity test and the tension adjustment process of the metal diaphragm are repeated again. This is repeated until the test sensitivity of the microphone in production is basically consistent with the reference sensitivity of the microphone, and the adjustment work is completed.

[0004] Although this method can test the sensitivity of the condenser microphone relatively quickly, the electrostatic actuator structure is to fix a circular metal plate with holes on an insulating ring structure, and then the ring structure is parallel to the clamping ring that fixes the metal diaphragm on the microphone to determine the distance. Such a structure has high requirements for parallelism and distance. Otherwise, under the same excitation voltage, the amplitude of the microphone metal diaphragm will produce a large error, and the accuracy of sensitivity detection cannot be guaranteed. Summary of the invention

[0005] 1. Technical problem to be solved by the invention The invention provides a microphone sensitivity test and adjustment device and method, which can solve the technical problem that the test results of the existing microphone sensitivity test and adjustment method have large errors.

[0006] 2. Technical solution

[0007] To solve the above problems, the technical solution provided by the present invention is: A microphone sensitivity test and adjustment device and method, comprising the following steps: S01, placing a reference microphone on the device, using a signal generator to output a sinusoidal signal A with a fixed frequency and amplitude to a metal diaphragm and a rear plate to make the metal diaphragm vibrate; S02, using a Doppler vibrometer to measure the displacement amplitude of the metal diaphragm in S01 and record it as X; S03, removing the reference microphone and replacing it with a microphone to be adjusted; S04, using a signal generator to output a sinusoidal signal A with a fixed frequency and amplitude to the microphone to be adjusted to make the metal diaphragm vibrate; S05, using a Doppler vibrometer to measure the displacement amplitude of the metal diaphragm in S04 and record it as Y; S06, comparing the difference between X and Y, and adjusting the tension of the metal diaphragm of the microphone to be adjusted; S07, repeating S05-S06 until the sensitivity of the adjustment microphone is consistent with that of the reference microphone.

[0008] Optionally, at least the displacement amplitude Y is calculated by selecting a period T of the diaphragm vibration caused by a regular workshop non-sinusoidal signal A, in which the metal diaphragm vibration displacement deviation is relatively gentle, and dividing it into two sections. In one period, no sinusoidal signal A is emitted, and the metal diaphragm vibration displacement at this time is recorded as Y1; in another period, a sinusoidal signal A is emitted, and the metal diaphragm vibration displacement at this time is recorded as Y2. The displacement amplitude Y can be obtained by comparing the difference between Y1 and Y2.

[0009] Optionally, the Doppler vibrometer detects the vibration amplitude of the central area of ​​the metal diaphragm.

[0010] A microphone sensitivity test and adjustment device comprises a microphone base, a microphone, a Doppler vibrometer and a signal generator, wherein the microphone base is arranged at the bottom of the microphone, the signal generator is electrically connected to the metal diaphragm and the back plate of the microphone through the microphone base, and the Doppler vibrometer is placed directly above the microphone to detect the displacement amplitude of the metal diaphragm.

[0011] Optionally, the metal diaphragm is connected to the microphone via a diaphragm ring.

[0012] Optionally, the Doppler vibrometer is placed directly above the microphone to detect the displacement amplitude of the central area of ​​the metal diaphragm.

[0013] 3. Beneficial effects

[0014] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: 1. It can solve the problem that the detection sensitivity of the electrostatic actuator is that the metal diaphragm and the circular metal plate of the electrostatic actuator cannot be guaranteed to be parallel, thus affecting the detection accuracy.

[0015] 2. It can solve the problem that the distance between the metal diaphragm and the circular metal plate of the electrostatic actuator changes during the tension adjustment of the metal diaphragm, thus affecting the detection accuracy.

[0016] 3. It can eliminate the noise caused by the vibration of the metal diaphragm caused by the vibration of the workstation, and the detection results are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of an existing microphone sensitivity test and adjustment device; Figure 2 A schematic diagram of the structure of a microphone sensitivity test and adjustment device proposed in an embodiment of the present invention; Figure 3 It is a schematic diagram of the vibration curve of the metal diaphragm caused by external interference; Figure 4 is a schematic diagram of period T in the vibration curve schematic diagram; 1. Microphone base; 2. Microphone; 3. Doppler vibrometer; 4. Signal generator; 5. Metal diaphragm; 6. Back plate; 7. Diaphragm ring. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0019] It should be noted that when an element is referred to as being "fixed to", "disposed on", "fixedly arranged on" or "installed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. Further, when an element is considered to be "fixedly connected to" another element, the two may be fixed in a detachable connection manner or in a non-detachable connection manner, such as socketing, snap-on, one-piece fixing, welding, etc., which can be achieved in the prior art and will not be repeated here. When an element is perpendicular or approximately perpendicular to another element, it means that the ideal state of the two is vertical, but due to the influence of manufacturing and assembly, there may be a certain vertical error. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0021] The “first” and “second” involved in the present invention do not represent specific quantities and orders, but are merely used to distinguish names.

[0022] Combined with Figure 2-Figure 4 A microphone sensitivity test and adjustment method of the present embodiment includes the following steps: S01, placing a reference microphone on the device, using a signal generator to output a sinusoidal signal A with a fixed frequency and amplitude to the metal diaphragm and the rear plate to make the metal diaphragm vibrate; S02, using a Doppler vibrometer to measure the displacement amplitude of the metal diaphragm in S01 and record it as X; S03, removing the reference microphone and replacing it with the microphone to be adjusted; S04, using a signal generator to output a sinusoidal signal A with a fixed frequency and amplitude to the microphone to be adjusted to make the metal diaphragm vibrate; S05, using a Doppler vibrometer to measure the displacement amplitude of the metal diaphragm in S04 and record it as Y; S06, comparing the difference between X and Y, and adjusting the tension of the metal diaphragm of the microphone to be adjusted; S07, repeating S05-S06, so that the difference between XY approaches 0, that is, the adjustment is completed, and at this time the sensitivity of the microphone to be adjusted is consistent with that of the reference microphone.

[0023] This microphone sensitivity test and adjustment method changes the traditional detection method of vibrating the metal diaphragm of the capacitor microphone through a standard sound source or an electrostatic exciter, and then detecting the sensitivity of the microphone by detecting the electrical signal output by the microphone. Instead, the signal generator outputs a sine wave signal with a fixed frequency and amplitude to the metal diaphragm and the back plate of the microphone. Because the microphone is a capacitor with an electric charge when working, when a sine wave signal with a fixed frequency and amplitude is input to the metal diaphragm and the back plate, the metal diaphragm will vibrate with the corresponding frequency and amplitude. At this time, the displacement signal of the metal diaphragm vibration is detected in real time by a Doppler vibrometer fixed just above the metal diaphragm. This signal presents a sine wave curve on the time axis. For the same microphone, the structure is consistent, the metal diaphragm mass is consistent, and the charge amount is consistent. When the tension of the metal diaphragm is consistent, when the signal generator gives the microphone the same sine wave signal, the vibration displacement generated by the metal diaphragm is also the same. Based on this principle, under the same sinusoidal wave signal input, we use a Doppler vibrometer to measure and output the vibration amplitude of the central area of ​​the metal diaphragm of the microphone to be adjusted, and compare it with the vibration amplitude of the central area of ​​the metal diaphragm of the adjusted microphone as a benchmark. When the difference between the two is too large, the tension of the metal diaphragm of the microphone to be adjusted is adjusted to make it consistent with the vibration amplitude of the benchmark microphone, thus completing the sensitivity adjustment of the microphone to be adjusted.

[0024] In the original electrostatic actuator solution, the assembly of the electrostatic excitation plate and the insulating ring structure will produce non-parallel errors. At the same time, the fixation of the diaphragm and the diaphragm ring on the microphone will also produce non-parallel errors. These errors will accumulate to form a large error, making it difficult to ensure the sensitivity accuracy of the produced microphone and the consistency is poor.

[0025] This microphone sensitivity test and adjustment method solves the problem in the original electrostatic actuator solution that the metal diaphragm is fixed on the diaphragm ring, and then the diaphragm ring is fitted on the microphone housing through threads or interference fit. During this process, the metal diaphragm will be supported by the annular edge on the microphone housing, and as the diaphragm ring continues to move downward, the metal diaphragm is continuously tightened, and the tension increases. During this process, the distance between the electrostatic excitation plate and the upper edge of the diaphragm ring remains unchanged, but the distance between the electrostatic excitation plate and the metal diaphragm changes, resulting in a second variable in addition to the tension of the metal diaphragm, and the test result is inaccurate. This microphone sensitivity test and adjustment method uses a method of directly measuring the vibration amplitude of the microphone metal diaphragm under a specific electrical signal, and the result is accurate and the adjustment consistency is good.

[0026] However, in workshop production, the metal diaphragm vibration is not only caused by the input sinusoidal signal A, but also by factors such as workshop noise and machine vibration. Therefore, in order to ensure accuracy, it is necessary to find a way to eliminate the metal diaphragm vibration caused by the non-sinusoidal signal A as much as possible. Fortunately, most microphone production workshops are automated, and their processes are repetitive, so the noise and vibration generated are also periodic. These factors cause the metal diaphragm vibration displacement to change with time. Figure 3 As shown. Therefore, a period of time with a relatively gentle deviation of the metal diaphragm vibration displacement of a period T can be selected and divided into two sections: t1-t2, t2-t3. No sinusoidal signal A is emitted in the time period t1-t2. At this time, the metal diaphragm vibration displacement Y1 is the metal diaphragm vibration caused by the non-sinusoidal signal A. A sinusoidal signal A is emitted in the time period t2-t3. At this time, the metal diaphragm vibrates under the combined effect of the signal and the noise in the workshop, the vibration of the machine and other influencing factors. At this time, the metal diaphragm vibration displacement is Y2. Y2-Y1 is the real displacement vibration Y of the metal diaphragm caused by the sinusoidal signal A, thus eliminating the noise. Figure 4 The dotted box contains the metal diaphragm displacement curve and noise elimination curve for a period T.

[0027] It should be noted that the reference microphone in S01 can be measured in an environment without external interference. In this case, X is the vibration amplitude of the metal diaphragm of the reference microphone. If the reference microphone is measured in an environment with external interference, the above method should also be used for measurement to eliminate noise.

[0028] As a preferred embodiment of the present invention, a device for implementing the above-mentioned microphone sensitivity test and adjustment method comprises a microphone base 1, a microphone 2, a Doppler vibrometer 3 and a signal generator 4, wherein the microphone base 1 is arranged at the bottom of the microphone 2, the signal generator 4 is electrically connected to the metal diaphragm 5 and the back plate 6 of the microphone 2 through the microphone base 1, and the Doppler vibrometer 3 is placed directly above the microphone 2 to detect the displacement amplitude of the central area of ​​the metal diaphragm 5. The Doppler vibrometer 3 is mainly used to detect the displacement amplitude of the center of the metal diaphragm 5, because the displacement amplitude of the center of the metal diaphragm 5 is the largest, and the detection result is more accurate.

[0029] As a preferred solution of the present invention, the metal diaphragm 5 is connected to the microphone 2 via a diaphragm ring 7 , and the diaphragm ring 7 is threadedly sleeved on the upper end of the microphone 2 .

[0030] The specific embodiments are as follows: When the DC polarization voltage U0 (generally 800V) superimposed with the AC signal u (about 30V-50V) is applied to the plate of the electrostatic actuator, the instantaneous electrostatic voltage p(t) generated on the diaphragm due to the Coulomb force is calculated by the following formula:

[0031] Where: p(t) is the equivalent instantaneous sound pressure, in Pascals; ε gas is the dielectric constant of the gas between the electrostatic actuator and the diaphragm, in F / m (farad per meter), (in air, ε gas =8.85*10 -12 F / m); d is the effective distance between the electrostatic actuator and the diaphragm, in m (meter); a is the ratio of the effective area of ​​the electrostatic actuator to the effective area of ​​the diaphragm; p is the root mean square value of the fundamental frequency sound pressure, in Pascals; t is time, the unit is s (seconds); U0 is the DC voltage applied between the electrostatic actuator and the microphone diaphragm, in V (volt); u is the RMS value of the AC voltage applied between the electrostatic actuator and the microphone diaphragm, in V (volts); ω is the angular frequency, measured in rad / s (radians per second).

[0032] The sensitivity adjustment of microphones in existing production processes is usually done by using an electrostatic actuator to give the metal diaphragm on the microphone a 30V (the amplitude is related to the distance between the electrostatic excitation plate and the metal diaphragm and the sound pressure level to be generated. The farther the distance or the greater the sound pressure level to be generated, the higher the required voltage) AC signal of about 500Hz. At this time, the diaphragm will vibrate up and down at a frequency of 1000Hz. The microphone used in the embodiment has a design sensitivity of 27mV / Pa. At this time, the output sound pressure level of the microphone should be 85dB. If the actual measured sound pressure level is not equal to 85dB, the tension of the metal diaphragm needs to be adjusted. It can be seen from the above formula that in this scheme, there are two main factors that affect the accuracy of the d value. First, the parallelism of the metal diaphragm 5 and the plane on the diaphragm ring 7 cannot be guaranteed, resulting in errors caused by the metal diaphragm and the electrostatic excitation plate being not parallel. The second is to tighten the tension of the metal diaphragm 5, which requires the diaphragm ring 7 to move downward. At this time, the metal diaphragm 5 is supported by the annular edge on the microphone housing and will not move downward. However, the electrostatic actuator is connected to the plane on the diaphragm ring 7. At this time, the distance between the metal diaphragm 5 and the excitation plate of the electrostatic actuator becomes closer, and the electrostatic force generated thereby becomes larger, so that the measured value is no longer just the result of adjusting the metal diaphragm.

[0033] In order to solve these two problems, a microphone with a sensitivity of 27mV / Pa is taken as an example in this embodiment. An AC sinusoidal signal A with an amplitude of 27mV and a frequency of 1000Hz is input from both ends of the metal diaphragm 5 and the rear plate 6 of the microphone. Under the action of the original charge, the metal diaphragm 5 will produce a corresponding vibration displacement Y, and the frequency is also 1000Hz. This Y can be measured by the Doppler vibrometer 3, and the vibration displacement Y of the same microphone corresponds to the sensitivity one by one. Assuming that the vibration displacement of the metal diaphragm of a microphone with a sensitivity of 27mV / Pa is X after the input of the AC sinusoidal signal A of 1000Hz, then the adjustment is completed by adjusting the tension of the metal diaphragm so that the vibration displacement Y is consistent with X. In this process, the position of the diaphragm in the area inside the annular edge of the microphone housing will never change, and the Doppler vibrometer 3 also measures the displacement data of the diaphragm (with an accuracy of up to 0.1nm), so the data accuracy is greatly improved.

[0034] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A microphone sensitivity test and adjustment method, characterized in that: The following steps are included: S01, placing a reference microphone on the device, using a signal generator to output a sinusoidal signal A with a fixed frequency and amplitude to the metal diaphragm and the rear plate to cause the metal diaphragm to vibrate; S02, using a Doppler vibrometer to measure the displacement amplitude of the metal diaphragm in S01 and record it as X; S03, remove the reference microphone and replace it with the microphone to be adjusted; S04, using a signal generator to output a sinusoidal signal A with a fixed frequency and amplitude to the microphone to be adjusted so that its metal diaphragm vibrates; S05, using a Doppler vibrometer to measure the displacement amplitude of the metal diaphragm in S04 and record it as Y; S06, comparing the difference between X and Y, and adjusting the tension of the metal diaphragm of the microphone to be adjusted; S07. Repeat S05-S06 until the sensitivity of the adjustment microphone is consistent with that of the reference microphone.

2. A microphone sensitivity test and adjustment method according to claim 1, characterized in that: At least the calculation method of the displacement amplitude Y is to select a period T of the diaphragm vibration caused by the regular workshop non-sinusoidal signal A, and divide it into two sections when the metal diaphragm vibration displacement deviation is relatively gentle. In one period of time, no sinusoidal signal A is emitted, and the metal diaphragm vibration displacement at this time is recorded as Y1; in another period of time, a sinusoidal signal A is emitted, and the metal diaphragm vibration displacement at this time is recorded as Y2. The displacement amplitude Y can be obtained by comparing the difference between Y1 and Y2.

3. A microphone sensitivity test and adjustment method according to claim 1 or 2, characterized in that: The Doppler vibrometer detects the vibration amplitude of the central area of ​​the metal diaphragm.

4. A microphone sensitivity test and adjustment device, characterized in that: The invention comprises a microphone base, a microphone, a Doppler vibrometer and a signal generator. The microphone base is arranged at the bottom of the microphone. The signal generator is electrically connected to the metal diaphragm and the rear plate of the microphone through the microphone base. The Doppler vibrometer is placed directly above the microphone to detect the displacement amplitude of the metal diaphragm.

5. The microphone sensitivity test and adjustment device according to claim 3, characterized in that: The metal diaphragm is connected to the microphone through a diaphragm ring.

6. A microphone sensitivity test and adjustment device according to claim 4 or 5, characterized in that: The Doppler vibrometer is placed just above the microphone to detect the displacement amplitude of the central area of ​​the metal diaphragm.

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