Electrostatic actuator for surface microphone and test method thereof

Abstract

The present invention discloses an electrostatic actuator for a surface microphone, comprising a base, an end cover and an electrostatic excitation plate, wherein the base and the end cover are both cylindrical structures, the end cover is sleeved on the top of the base, the electrostatic excitation plate is mounted on the end cover, a lower coupling cavity is provided at the center of the upper surface of the base, an upper coupling cavity is provided at the center of the lower surface of the end cover, and an electrostatic excitation channel is also provided through the center of the end cover. The purpose of the present invention is to provide an electrostatic actuator that can generate a static pressure of a specified sound pressure level and a specified frequency on a surface microphone diaphragm in a long-term stable manner.

Description

Technical Field

[0001] The invention relates to the technical field of microphones, and in particular to an electrostatic actuator for a surface microphone and a testing method thereof. Background Art

[0002] Aerodynamic noise refers to the noise generated by the internal movement of airflow or the interaction between airflow and objects. It dominates aircraft noise and motor vehicle noise. In today's society, noise pollution is becoming increasingly serious. Many countries have formulated relevant standards to restrict it. Reducing aerodynamic noise has always been a research hotspot in the motor vehicle industry and aviation field. Surface microphones are special microphones for measuring aerodynamic noise. They are widely used in noise sound pressure tests on the surfaces of motor vehicles or aircraft. In order to meet the special requirements of aerodynamic noise testing, the mechanical dimensions and electroacoustic characteristics of surface microphones are specially designed, which makes it impossible to use them with existing electrostatic actuators. The electrostatic actuator method uses a specially designed electrostatic actuator driven by a voltage with uniform amplitude-frequency characteristics to act on the surface of the microphone diaphragm to generate an electrostatic force that simulates sound pressure uniformly distributed on the surface of the diaphragm. At present, the electrostatic actuator method is mainly used to measure the relative frequency response of the microphone. It is a simple and quick method and one of the main methods for measuring the frequency response of the microphone.

[0003] Due to the particularity of the surface microphone structure, several problems will arise if conventional calibration equipment is used: ① The surface microphone cannot be inserted into the coupling cavity and can only be transferred using a transfer tool. However, there is a diameter change in the transfer link, and the sound field will be distorted at the diameter change. Specifically, the cross-section at the diameter change will produce radial reflected sound waves, resulting in uneven sound fields on both sides of the diameter change section; ② The diameter of the surface microphone is generally larger than the diameter of the conventional coupling cavity and the matching gland clamp, so it is difficult to install firmly and is not easy to align.

[0004] Another example is the Chinese patent publication: CN219121540U, which discloses an electrostatic actuator, electrostatic excitation device and system for a microphone, which is installed on a microphone protective cover. However, the electrostatic excitation protective cover includes an electrostatic excitation plate and a fixing mechanism for fixing the electrostatic excitation plate on the microphone, and is not coupled to the flat structure of the surface microphone. The electrostatic excitation method requires that the effective distance d between the electrostatic actuator and the microphone diaphragm is generally about 0.4mm-0.7mm. Therefore, this structure cannot meet the electrostatic excitation method test requirements of the surface microphone in practical applications. Another example is the Chinese patent publication: CN206865745U, which discloses a capacitive microphone frequency response measurement system. Since this method is very sensitive to the distance between the electrostatic actuator and the microphone diaphragm, and the diaphragm depths of different microphones are also different, resulting in a relatively large uncertainty, it is not suitable for calibrating the microphone sensitivity level. Summary of the invention

[0005] The object of the present invention is to provide an electrostatic actuator which can generate a static pressure of a specified sound pressure level and a specified frequency on a surface microphone diaphragm which is stable for a long time.

[0006] To solve the above problems, the technical solution provided by the present invention is:

[0007] An electrostatic exciter for a surface microphone comprises a base, an end cover and an electrostatic excitation plate, wherein the base and the end cover are both cylindrical structures, the end cover is sleeved on the top of the base, the electrostatic excitation plate is mounted on the end cover, a lower coupling cavity is provided at the center of the upper surface of the base, an upper coupling cavity is provided at the center of the lower surface of the end cover, and an electrostatic excitation channel is also provided through the center of the end cover.

[0008] Optionally, the base includes a fixed base and a movable base, the movable base can be movably inserted into the fixed base up and down, the lower coupling cavity is arranged on the top of the movable base, and the movable base is elastically connected to the fixed base through a spring.

[0009] Optionally, an anti-slip boss is provided at the bottom of the movable base, and an anti-slip step cooperating with the anti-slip boss is provided on the fixed base.

[0010] Optionally, the end cover includes an upper end cover and a lower end cover, the upper end cover is rotatably connected to the lower end cover, the lower coupling cavity is arranged on the lower end cover, the electrostatic excitation plate is installed on the upper end cover, and the lower end cover is sleeved on the top of the base.

[0011] Optionally, the outer peripheral walls of the upper end cover and the lower end cover are provided with scale markings that match each other.

[0012] Optionally, the lower end cover and the base are locked by a positioning pin.

[0013] Optionally, a microphone base is detachably connected to the top of the movable base, the upper coupling cavity is arranged on the microphone base, and the lower end cover is detachably connected to the upper end cover.

[0014] A test method for an electrostatic actuator comprises the following steps: S1, first placing a surface microphone into a lower coupling cavity of a base; S2, then sleeve an upper boss portion of the surface microphone into an upper coupling cavity of an end cover; S3, pressing down the surface microphone by pressing down the upper end cover to achieve locking; S4, energizing an electrostatic excitation board for testing.

[0015] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0016] The electrostatic actuator of the surface microphone is designed with a coupling cavity according to the flat structure of the surface microphone. The surface microphone can be completely coupled into the electrostatic actuator cavity. The inner diameter of the upper coupling cavity is the same as the outer diameter of the upper boss of the surface microphone, and the inner diameter of the lower coupling cavity is the same as the outer diameter of the lower boss of the surface microphone, so that a perfect fit in structure is achieved. The surface microphone is fully constrained and fixed through high-precision coupling of the upper and lower coupling cavities, so that the surface microphone diaphragm is aligned with the center of the electrostatic excitation plate. During testing, the surface microphone is firmly installed in the electrostatic actuator and is easy to align during installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic structural diagram of an electrostatic actuator for a surface microphone proposed in an embodiment of the present invention;

[0018] Figure 2 A cross-sectional schematic diagram of an electrostatic actuator for a surface microphone provided by an embodiment of the present invention;

[0019] Figure 3 A schematic structural diagram of an end cover in an electrostatic actuator of a surface microphone proposed in an embodiment of the present invention;

[0020] 1. Base; 1a. Lower coupling cavity; 11. Fixed base; 12. Movable base; 13. Spring; 14. Anti-slip boss; 15. Anti-slip step; 2. End cover; 2a. Upper coupling cavity; 2b. Electrostatic excitation channel; 21. Upper end cover; 22. Lower end cover; 3. Electrostatic excitation plate; 4. Positioning pin. DETAILED DESCRIPTION

[0021] 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.

[0022] It should be noted that when an element is referred to as being "fixed to", "disposed on", "fixed 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 fixation, 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.

[0023] 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.

[0024] The “first” and “second” involved in the present invention do not represent specific quantities and orders, but are merely used to distinguish names.

[0025] Combined with Figure 1-Figure 3 The electrostatic exciter of a surface microphone of the present embodiment comprises a base 1, an end cover 2 and an electrostatic excitation plate 3. Both the base 1 and the end cover 2 are cylindrical structures. The end cover 2 is sleeved on the top of the base 1. A circular fixing groove matching the base 1 is provided on the lower surface of the end cover 2. The electrostatic excitation plate 3 is mounted on the end cover 2 and is located on the top of the end cover 2. A lower coupling cavity 1a is provided at the center of the upper surface of the base 1. An upper coupling cavity 2a is provided at the center of the lower surface of the end cover 2. The lower coupling cavity 1a is aligned with the upper coupling cavity 2a. The center of the electrostatic excitation plate 3 is aligned with the centers of the upper and lower coupling cavities. An electrostatic excitation channel 2b is also provided through the center of the end cover 2. The electrostatic excitation channel 2b extends from the upper coupling cavity 2a to the upper surface of the end cover 2. The distance between the electrostatic excitation plate 3 and the upper coupling cavity 2a remains unchanged. The upper coupling cavity 2a and the lower coupling cavity 1a can be regarded as two flat circular grooves.

[0026] The electrostatic actuator of the surface microphone is designed with a coupling cavity according to the flat structure of the surface microphone. The surface microphone can be completely coupled into the electrostatic actuator cavity. The inner diameter of the upper coupling cavity 2a is the same as the outer diameter of the upper boss of the surface microphone, and the inner diameter of the lower coupling cavity 1a is the same as the outer diameter of the lower boss of the surface microphone, so that a perfect fit is achieved in structure. The surface microphone is fully constrained and fixed through high-precision coupling of the upper and lower coupling cavities, so that the surface microphone diaphragm is aligned with the center of the electrostatic excitation plate 3. During testing, the surface microphone is firmly installed in the electrostatic actuator and is easy to align during installation.

[0027] As a preferred solution of the present invention, the base 1 includes a fixed base 11 and a movable base 12. Both the fixed base 11 and the movable base 12 are cylindrical structures. The movable base 12 can be inserted in the center of the fixed base 11 and can be moved up and down. The lower coupling cavity 1a is arranged at the top of the movable base 12. The movable base 12 is elastically connected to the fixed base 11 through a spring 13. The spring 13 is arranged at the bottom of the movable base 12 and is used to lift the movable base 12 upward. The bottom of the spring 13 is connected to a spring mounting plate, and the spring mounting plate is detachably connected to the base 1 through screws. Combined with the pressure converted from the tension of the spring 13, the surface microphone is sleeved and pressed on the plane of the upper coupling cavity 2a to achieve a fixed and centered effect. The spring 13 of the base 1 provides a locking force to ensure stability and reliability during the test.

[0028] As a preferred solution of the present invention, an anti-slip boss 14 is provided at the bottom of the movable base 12, and the outer diameter of the anti-slip boss 14 is larger than the outer diameter of the movable base 12. An anti-slip step 15 cooperating with the anti-slip boss 14 is provided on the fixed base 11. When the movable base 12 moves upward until the anti-slip boss 14 abuts against the anti-slip step 15, the movable base 12 cannot continue to move upward, thereby preventing the movable base 12 from being fixed outward by the spring 13.

[0029] As a preferred embodiment of the present invention, the end cover 2 includes an upper end cover 21 and a lower end cover 22, the centers of the upper end cover 21 and the lower end cover 22 and the center of the base 1 are on the same vertical axis, the upper end cover 21 is rotatably connected to the lower end cover 22, the upper end cover 21 can rotate relative to the lower end cover 22, the lower coupling cavity 1a is arranged on the lower end cover 22, the electrostatic excitation plate 3 is installed on the upper end cover 21, and the lower end cover 22 is sleeved on the upper part of the base 1, the upper cover part can rotate 360 ​​degrees, and the test angle can be switched at will, when the microphone needs to be calibrated and tested at multiple angles during the calibration process, the top cover part is rotated, and the microphone can realize the angle switching of the electrostatic excitation plate 3 in the locked state, and because the flatness of the installation surface of the electrostatic excitation plate 3 meets the standard, the electrostatic excitation plate 3 can always be kept at a fixed distance above the surface microphone diaphragm during the rotation process, and the manual disassembly part is reduced during the calibration process, thereby avoiding the error caused by disassembly and improving the consistency of each test.

[0030] As a preferred solution of the present invention, the outer peripheral walls of the upper end cover 21 and the lower end cover 22 are provided with matching scale marks. Before starting the test, the zero scale line of the upper end cover 21 is aligned with the zero scale line of the lower end cover 22.

[0031] As a preferred solution of the present invention, the end cover 2 and the base 1 are locked by the positioning pin 4. The end cover 2 is provided with a locking groove that cooperates with the positioning pin 4. The locking grooves are arranged in a circumferential array on the left and right sides of the end cover 2. The locking grooves include a straight groove extending to the lower end surface of the end cover 2 and a circumferential groove arranged at the upper end of the straight groove. The circumferential groove is arranged along the clockwise or counterclockwise direction of the end cover 2, but it is necessary to ensure that the direction of the circumferential groove is opposite to the rotation direction of the upper end cover 21. The positioning pin 4 enters the circumferential groove through the straight groove to achieve the locking action of the base 1 and the end cover 2.

[0032] As a preferred embodiment of the present invention, a microphone base is detachably connected to the top of the movable base 12, the diameter of the microphone base is consistent with the diameter of the movable base 12, the upper coupling cavity 2a is arranged on the microphone base, and the lower end cover 22 is detachably connected to the upper end cover 21. Both the microphone base and the lower end cover 22 are replaceable designs, which can effectively make up for the technical defects of the existing electrostatic actuator coupling cavity being unsuitable and having poor versatility.

[0033] The working principle of the electrostatic actuator of the surface microphone is as follows: the electrostatic excitation plate 3 is located at a fixed distance above the surface microphone diaphragm, forming a relative effective area with the surface of the microphone diaphragm, and the electrostatic excitation plate 3 is used to electrically connect to the excitation signal generating device, and receive the sinusoidal signal output by the excitation signal generating device to eliminate the DC voltage; the upper end cover 21 can be manually rotated relative to the lower end cover 22, which drives the relative rotation of the electrostatic excitation plate 3 and the surface microphone, and cooperates with the scale system of the upper and lower end covers to realize arbitrary precise angle switching of the electrostatic excitation plate 3.

[0034] During calibration, first place the surface microphone into the lower coupling cavity 1a of the base 1, then put the upper boss of the surface microphone into the upper coupling cavity 2a of the end cover 2, and press the upper end cover 21 down to press the surface microphone down until the upper cover is buckled into the positioning pin 4 to achieve locking, and then the electrostatic excitation board 3 is powered on for testing. When the microphone needs to be calibrated and tested at multiple angles during the calibration process, just rotate the top cover.

[0035] 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. An electrostatic actuator for a surface microphone, characterized in that: The device comprises a base, an end cover and an electrostatic excitation plate, wherein the base and the end cover are both cylindrical structures, the end cover is sleeved on the top of the base, the electrostatic excitation plate is installed on the end cover, a lower coupling cavity is provided at the center of the upper surface of the base, an upper coupling cavity is provided at the center of the lower surface of the end cover, and an electrostatic excitation channel is also provided through the center of the end cover; The inner diameter of the upper coupling cavity is the same as the outer diameter of the upper boss of the surface microphone, the inner diameter of the lower coupling cavity is the same as the outer diameter of the lower boss of the surface microphone, the lower coupling cavity is aligned with the upper coupling cavity, and the center of the electrostatic excitation plate is aligned with the center of the upper and lower coupling cavities; The end cover comprises an upper end cover and a lower end cover, the upper end cover is rotatably connected to the lower end cover, the lower coupling cavity is arranged on the lower end cover, the electrostatic excitation plate is installed on the upper end cover, and the lower end cover is sleeved on the top of the base; The base comprises a fixed base and a movable base, the movable base can be inserted into the fixed base movably up and down, the lower coupling cavity is arranged on the top of the movable base, and the movable base is elastically connected to the fixed base through a spring.

2. The electrostatic actuator for a surface microphone according to claim 1, characterized in that: An anti-dropping boss is provided at the bottom of the movable base, and an anti-dropping step matched with the anti-dropping boss is provided on the fixed base.

3. The electrostatic actuator for a surface microphone according to claim 1, characterized in that: The outer peripheral walls of the upper end cover and the lower end cover are provided with scale marks that match each other.

4. The electrostatic actuator for a surface microphone according to claim 1, characterized in that: The lower end cover and the base are locked by a positioning pin.

5. The electrostatic actuator for a surface microphone according to claim 1, characterized in that: The top of the movable base is detachably connected with a microphone base, the upper coupling cavity is arranged on the microphone base, and the lower end cover is detachably connected to the upper end cover.

6. A method for testing an electrostatic actuator for a surface microphone according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. First, place the surface microphone into the lower coupling cavity of the base; S2, then put the upper boss part of the surface microphone into the upper coupling cavity of the end cover; S3. Press down the upper end cover to lock the surface microphone; S4. The electrostatic excitation board is powered on for testing.

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