Remote microphone calibration apparatus and method, acoustic measuring apparatus and calibration method

Abstract

The application discloses a remote microphone calibration device and method, an acoustic measuring instrument and a calibration method. The device comprises an initial signal generating unit, which outputs a sine signal matched with a calibration frequency; an electrostatic excitation signal generating unit, which is electrically connected with the initial signal generating unit, receives the sine signal output by the initial signal generating unit, processes and outputs a high-voltage alternating current signal meeting a preset equivalent sound pressure level; an electrostatic exciter, which is electrically connected with the electrostatic excitation signal generating device; the electrostatic exciter is installed above a microphone diaphragm at a fixed distance and forms a relative effective area with the surface of the microphone diaphragm; the electrostatic exciter receives the high-voltage alternating current signal and generates a static pressure relative to the microphone diaphragm; and a control unit, which receives a remote calibration instruction and starts the initial signal generating unit. The target calibration precision of the remote calibration microphone reaches a level of 2 or above.

Description

Technical Field

[0001] This application relates to the field of acoustic measurement, and more particularly to an acoustic measurement method and an acoustic measuring instrument, specifically a remote microphone calibration device and method, an acoustic measuring instrument and calibration method. Background Technology

[0002] Automatic noise monitoring technology involves multiple aspects, including industrial noise, construction noise, transportation noise, and social noise, requiring qualified automatic environmental noise monitoring instruments. Since monitoring agencies are responsible for the accuracy of the monitoring data, quality control measures need to be established to ensure the traceability of measurement values. Since automatic environmental noise monitoring instruments are installed in different outdoor locations, daily on-site calibration with a sound calibrator is impractical. Therefore, automatic environmental noise monitoring instruments should have remote automatic calibration capabilities, and the calibration accuracy should meet the accuracy requirements for Class 2 and above sound calibrators in GB / T 15173-2010 Electroacoustic Sound Calibrators. Currently, domestically produced instruments of this type can only perform remote automatic calibration of the internal electrical signal section of the main unit, not the noise sensor section. However, the noise sensor is a key component of automatic environmental noise monitoring instruments, sound level meters, and other instruments. The sensitivity of the noise sensor changes due to various factors such as temperature and humidity, self-charge loss, and impacts, making regular calibration necessary.

[0003] A sound calibrator is a device that, when coupled to a microphone of a specified type and structure, generates sinusoidal sound pressure levels and frequencies at a specified frequency; it requires on-site operation. The electrostatic exciter method, on the other hand, uses a specially designed electrostatic exciter driven by a voltage with uniform amplitude-frequency characteristics to generate static pressure on the microphone diaphragm surface, simulating sound pressure uniformly distributed across the diaphragm surface. Currently, the electrostatic exciter method is mainly used to determine the relative frequency response of microphones; it is a simple and quick method and one of the main methods for determining microphone frequency response. However, this method is highly sensitive to the distance between the electrostatic exciter and the microphone diaphragm, and the diaphragm depth varies among different microphones, resulting in significant uncertainty and making it unsuitable for calibrating microphone sensitivity levels. Furthermore, it is relatively bulky and unsuitable for use on noise measuring instruments.

[0004] Some imported instruments, such as those from Denmark's B&K (Brüel & Kjær), employ Charge Injection Calibration (CIC; invented by Brüel & Kjær in the mid-1990s), which can be used to verify the integrity of the measurement channel (including the microphone body) of a condenser microphone. This technique is sensitive to any changes in the capacitance of the microphone body and any variations in the connected preamplifier (and cables), and can also be used as a quality control method. However, technically, CIC is not a "calibration" method. Summary of the Invention

[0005] This application addresses the shortcomings of existing technologies by proposing a microphone calibration method that enables remote control.

[0006] A remote microphone calibration device, comprising:

[0007] The initial signal generation unit outputs a sinusoidal signal that matches the calibration frequency;

[0008] An electrostatic excitation signal generating unit is electrically connected to an initial signal generating unit, receives the sinusoidal signal output by the initial signal generating unit, processes it, and outputs a high-voltage AC signal that meets the preset equivalent sound pressure level.

[0009] An electrostatic exciter, electrically connected to an electrostatic excitation signal generator;

[0010] An electrostatic exciter is installed at a fixed distance above the microphone diaphragm, forming a relatively effective area with the surface of the microphone diaphragm. The electrostatic exciter receives the high-voltage AC signal and generates static pressure relative to the microphone diaphragm.

[0011] The control unit receives remote calibration commands and starts the initial signal generation unit.

[0012] The preset equivalent sound pressure level is calculated based on the initial sensitivity level of the microphone obtained under the action of the sound calibrator, and the calibration frequency is the standard frequency of the sound calibrator.

[0013] As one implementation, the electrostatic excitation signal generating unit includes the following structure:

[0014] The voltage regulation unit is used to regulate the voltage so that the high-voltage AC signal output by the boost unit meets the preset equivalent sound pressure level.

[0015] The signal amplification unit amplifies the sinusoidal AC signal at the primary stage.

[0016] A DC blocking unit is used to eliminate the DC signal superimposed on the sinusoidal signal;

[0017] The boost unit is used to boost the sinusoidal AC signal to a high-voltage AC signal, and the output high-voltage AC signal meets the preset equivalent sound pressure level.

[0018] Based on the above structure, a remote microphone calibration method is also proposed, including the following steps:

[0019] Upon receiving a remote calibration command, the initial signal generation unit is activated to generate a sinusoidal signal.

[0020] The sinusoidal signal is processed by the electrostatic excitation signal generation unit and output as a high-voltage AC signal that meets the preset equivalent sound pressure level, and then output to the electrostatic exciter.

[0021] The electrostatic pressure relative to the microphone diaphragm is generated by an electrostatic exciter, and the microphone outputs a corresponding electrical signal.

[0022] The sensitivity level of the current microphone is calculated based on the electrical signal and the preset equivalent sound pressure level.

[0023] The method for adjusting the high-voltage AC signal that satisfies the preset equivalent boost stage includes the following steps:

[0024] The microphone is initialized and calibrated using an acoustic calibrator to generate an initial sensitivity level Lx;

[0025] An electrostatic excitation signal is obtained through an electrostatic excitation signal generating unit. The electrostatic excitation signal output by the electrostatic excitation signal generating unit is adjusted according to the initial sensitivity level so that it acts on the electrostatic exciter to achieve a preset calibration sound pressure level.

[0026] The electrostatic excitation signal that meets the preset calibration sound pressure level requirement is saved.

[0027] A further method for calibrating an acoustic measuring instrument is provided, the steps of which include a remote microphone calibration method.

[0028] A further acoustic measuring instrument is provided, including the remote microphone calibration device, and also including a microphone, a preamplifier, a host, and a remote interactive interface.

[0029] The beneficial effects of this application are as follows: By improving the electrostatic exciter, it is installed on the microphone to generate a long-term stable static pressure at a specified sound pressure level and frequency on the microphone diaphragm. The excitation signal that meets the conditions is generated and output to the electrostatic exciter through remote control, thereby realizing the remote control of the microphone and acoustic measuring instrument. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a structural block diagram of the remote microphone calibration device disclosed in Embodiment 1;

[0032] Figure 2 Schematic diagram of the microphone and electrostatic exciter;

[0033] Figure 3 This is a block diagram illustrating the principle of electrostatic excitation signal generation.

[0034] Figure 4 This is a flowchart of the electrostatic excitation calibration sound pressure level adjustment process;

[0035] Figure 5 This is a flowchart of the remote automatic calibration process;

[0036] Figure 6 It is a protective cover for an integrated electrostatic exciter;

[0037] Figure 7 It is a device for applying electrostatic excitation signals. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0039] Example 1:

[0040] This application proposes a remote calibration concept for acoustic measuring instruments. Based on this concept, this embodiment discloses a remote microphone calibration device. The idea is to generate a long-term stable static pressure level and a specified frequency on the microphone diaphragm through remote control. This device can then be applied to acoustic measuring instruments such as automatic environmental noise monitors and sound level meters to calibrate the microphone sensitivity.

[0041] A remote microphone calibration device, such as Figure 1 It includes the following structures:

[0042] The initial signal generation unit outputs a sinusoidal signal that matches the calibration frequency;

[0043] The electrostatic excitation signal generating unit is electrically connected to the initial signal generating unit, receives the sinusoidal signal output by the initial signal generating unit, processes it and outputs a high-voltage AC signal that meets the preset equivalent sound pressure level, and outputs it as the electrostatic excitation signal.

[0044] An electrostatic exciter, electrically connected to an electrostatic excitation signal generator;

[0045] An electrostatic exciter is installed at a fixed distance above the microphone diaphragm, forming a relatively effective area with the surface of the microphone diaphragm. The electrostatic exciter receives the high-voltage AC signal and generates static pressure relative to the microphone diaphragm.

[0046] The control unit receives remote calibration commands and starts the initial signal generation unit.

[0047] The preset equivalent sound pressure level is calculated based on the initial sensitivity level of the microphone obtained under the action of the sound calibrator, and the calibration frequency is the standard frequency of the sound calibrator.

[0048] In this scheme, the traditional electrostatic exciter structure is improved and installed on the microphone diaphragm, so that it acts on the microphone diaphragm to generate a stable static pressure level and a specified frequency.

[0049] According to the principle of electrostatic excitation, the electrostatic excitation plate in the electrostatic excitation device is a conductive rigid plate. When placed nearly parallel to the microphone diaphragm, it forms a capacitor together with the equally conductive microphone diaphragm. Figure 2 It has a microphone housing 1 and a microphone diaphragm 2 with an area of ​​S. dia ; Electrostatic exciter 3, with an area of ​​S act .

[0050] When a time-varying voltage is applied between the electrostatic excitation plate and the microphone diaphragm, the exciter generates a force F distributed on the surface of the microphone diaphragm, as shown in formula (1).

[0051] ………………………… (1)

[0052] ……………………(2)

[0053] In the formula:

[0054] F — The electrostatic force generated on the diaphragm (the thrust and tension are considered as positive and negative forces, respectively), measured in Newtons (N);

[0055] p act — The pressure generated by static electricity on a diaphragm, measured in Pascals (Pa).

[0056] ε gas — The dielectric constant of the air between the actuator and the diaphragm, expressed in farads per meter (F / m). (In air: εgas =8.85×10 -12 F / m);

[0057] d — The effective distance between the actuator and the diaphragm, in meters (m);

[0058] S dia —Effective area of ​​the diaphragm, in square meters (m²) 2 );

[0059] S act —The effective surface area of ​​the actuator above the effective area of ​​the diaphragm, in square meters (m²). 2 );

[0060] a = S act / S dia —The ratio of the effective area of ​​the actuator to the effective area of ​​the diaphragm;

[0061] U — Voltage applied between the exciter and the microphone diaphragm, in units of (V).

[0062] Pressure generated by force F P act As shown in equation (2), this pressure causes the microphone diaphragm to vibrate, which is similar to the vibration produced by sound pressure acting on the diaphragm of a test capacitor microphone. The ratio of the effective area of ​​the electrostatic exciter to the effective area of ​​the diaphragm is a constant, usually around 1 / 2.

[0063] When measuring the frequency response of a microphone, the exciter usually operates under a DC voltage and a superimposed sinusoidal AC voltage. Equation (3) describes the instantaneous electrostatic pressure under this operating mode.

[0064] …………………… (3)

[0065] Equations (4), (5), and (6) describe the components of the induced electrostatic pressure, including the desired fundamental frequency equivalent sound pressure. p And two undesirable second harmonic sound pressure levels p d static pressure p stat .

[0066] ………………………………………(4)

[0067] ……………………………………(5)

[0068] ………………………(6)

[0069] In the formula:

[0070] p(t) — Equivalent instantaneous sound pressure level, in Pascals (Pa);

[0071] p — The root mean square value of the fundamental frequency sound pressure level, in Pascals (Pa).

[0072] p d — The root mean square value of the sound pressure level at the second harmonic frequency, in Pascals (Pa).

[0073] p stat — Static pressure, measured in Pascals (Pa);

[0074] t — Time, in seconds (s);

[0075] U 0 — The DC voltage applied between the exciter and the microphone diaphragm, in volts (V).

[0076] u — The root mean square value of the AC voltage applied between the exciter and the microphone diaphragm, in volts (V).

[0077] ω — Angular frequency, measured in radians per second (rad / s).

[0078] From formula (2), it can be seen that the pressure P on the microphone diaphragm is... act With ε gas , d, a and U are related, while ε gas Since 'a' is a fixed value and 'U' is an electrical signal, a stable output value can be generated. Therefore, to produce a stable calibration signal P... act To ensure this, the effective distance d between the exciter and the diaphragm must remain essentially constant. To address this issue, this embodiment proposes firmly fixing the electrostatic exciter to the microphone protective cover, using an insulating material with minimal deformation due to temperature and humidity variations for isolation and fixation. This ensures the pressure P... act If stable, the pressure P on the microphone diaphragm can be remotely adjusted via U. act The size of the device allows for remote electrostatic excitation calibration.

[0079] According to formulas (4) and (5), the effective distance d between the electrostatic exciter and the microphone diaphragm is generally about 0.5 mm. To ensure a good signal-to-noise ratio, reduce the influence of background noise, and reduce the influence of the second harmonic, the DC voltage applied to the electrostatic exciter is generally 800 V, and the superimposed sinusoidal AC voltage is about 45 Vrms. At this time, the fundamental frequency equivalent sound pressure p is about 0.63 (pa), and the equivalent sound pressure level is about 90 dB. This places high demands on the equipment that generates the electrostatic excitation signal, and the equipment is very large. Therefore, this method is mainly suitable for use under similar laboratory conditions, and the superposition of multiple voltages will also increase the uncertainty of the generated signal.

[0080] Therefore, this application proposes the use of second harmonic P. d The calibration method is as follows, and the DC voltage U0 is filtered out. At this time, the instantaneous pressure p(t) is:

[0081] ………………………(7)

[0082] ε gas =8.85×10 -12 F / m and a are approximately equal to 0.5. Even after the electrostatic exciter is integrated into the microphone protective cover, the distance d remains essentially unchanged. Therefore, P... act The magnitude of the sound pressure is only related to the applied AC signal u. Taking d = 0.5 mm as an example, when u is 134V, an equivalent sound pressure of about 0.63 Pa can be generated. Since the electrostatic excitation method does not form an electrical circuit, the driving current can be very small, the device size can be very small, and it is easier to implement in hardware, making it suitable for practical remote calibration needs.

[0083] The specified sound pressure level and frequency are defined as a high-voltage AC signal with an equivalent sound pressure level that satisfies the initial sensitivity of the microphone, and the device that generates this high-voltage AC signal that meets the requirements is, for example... Figure 1 and Figure 3 Specifically, it includes:

[0084] The system comprises a control unit, an initial signal generation unit, and an electrostatic excitation signal generation unit. The initial signal generation unit receives instructions from the control unit to generate a sine wave with a frequency of 1 / 2 standard. For example, in a DAC module, after receiving a calibration start command, the control unit controls the DAC module to generate a sine wave with a frequency of 1 / 2 standard and an amplitude of approximately 1 Vrms.

[0085] The electrostatic excitation signal generator includes a DC blocking unit, a voltage regulation unit, a signal amplification unit, and a boost unit. This application proposes two embodiments of the electrostatic excitation signal generator, one of which is:

[0086] The initial signal generation unit is connected to the input terminal of the voltage regulation unit, the output terminal of the voltage regulation unit is connected to the input terminal of the signal amplification unit, the output terminal of the signal amplification unit is connected to the DC blocking unit, and the output terminal of the DC blocking unit is connected to the boost unit.

[0087] Among them, the DC blocking unit is used to eliminate the DC signal superimposed on the sinusoidal signal, thereby eliminating the fundamental frequency signal induced on the diaphragm and meeting the second harmonic calibration requirements; such as using a DC blocking capacitor.

[0088] A voltage regulation unit is used to regulate the voltage so that the high-voltage AC signal output by the boost unit meets the equivalent sound pressure level of the microphone's initial sensitivity; such as an adjustable potentiometer, the output voltage can be manually adjusted to meet the equivalent sound pressure level.

[0089] The signal amplification unit amplifies the primary sinusoidal AC signal. The amplification factor of the signal amplification unit is composed of a dual-supply low-noise single operational amplifier. The primary amplification factor can be set according to the supply voltage, and it is advisable to amplify by 5-10 times to ensure that the signal is not distorted.

[0090] If the input voltage amplitude is about 1 Vrms, then the AC voltage signal output by the signal amplification unit after adjustment is about 5 Vrms. According to the design goal of this scheme, the signal needs to be boosted to about 150 Vrms.

[0091] A boost unit is used to boost a sinusoidal AC signal to a high-voltage AC signal, which is applied to an electrostatic exciter.

[0092] Regarding the selection of the boost unit, if a power amplifier is used for boosting, positive and negative high-voltage power supply modules and a power amplifier circuit are required, resulting in a relatively large size and high power consumption. Since electrostatic excitation calibration does not form an electrical loop, the current flowing through it is very small. Therefore, this embodiment uses a small-sized, low-power boost transformer with a smooth frequency response of 125 Hz to 1 kHz and low distortion at 200 Vrms. In practice, selection should be based on available products on the market.

[0093] Secondly, as another implementation scheme, another DC blocking unit, such as a DC blocking capacitor, is electrically connected between the signal amplification unit and the initial signal generation unit. Considering that the connection relationships of different circuit structures may vary, the position of the DC blocking unit in the excitation signal generation unit can be adjusted to eliminate DC signals. No detailed restrictions are placed on the specific circuit structure and the use of electronic components.

[0094] According to the method disclosed above, it is theoretically possible to achieve the goal of measuring the absolute sensitivity of the microphone. However, due to the limitations of the measuring tools, the accuracy of measuring the effective distance d between the electrostatic exciter and the microphone diaphragm and the ratio a of the effective area of ​​the electrostatic exciter and the effective area of ​​the microphone diaphragm is uncertain.

[0095] Therefore, this application further discloses a calibration method based on an acoustic calibrator. Specifically, an initialization calibration, specifically a sound pressure level adjustment step, is performed before implementing the remote calibration method. First, the microphone is calibrated using a standard sound source with an accuracy of level 1 or higher (such as an acoustic calibrator or piston generator) to generate an initial sensitivity level Lx. An electrostatic excitation signal is then obtained through an electrostatic excitation signal generation unit. The electrostatic excitation signal output by the electrostatic excitation signal generation unit is adjusted according to the initial sensitivity level, so that it acts on the electrostatic exciter to achieve a preset calibration sound pressure level. The initial electrostatic excitation signal that achieves the preset calibration sound pressure level is then saved. Using this method, electrostatic excitation calibration can achieve an accuracy of level 2 or higher. Therefore, the electrostatic excitation signal generation device needs to include a voltage adjustment unit. By adjusting the voltage adjustment unit, the voltage output to the electrostatic exciter is controlled to reach the equivalent sound pressure level required for the sensitivity level calibrated by the acoustic calibrator.

[0096] Figure 4 To calibrate the sound pressure level adjustment process, firstly, a sound calibrator or piston generator with a precision of level 1 or above is used for calibration. Taking a level 1 sound calibrator of 1 kHz / 94 dB as an example, after starting the calibration, the control unit (MCU) calculates the short-time equivalent sound pressure level Leq(t) according to formula (8) and automatically adjusts Lx until Leq(t) is equal to a stable 94 dB.

[0097] Leq(t) = 20 * lg(Av)-Lx+94……………………(8)

[0098] In the formula:

[0099] Leq(t) – equivalent sound pressure level in 1 second, in dB;

[0100] Av — The effective voltage value within 1 second, in V;

[0101] Lx – Sensitivity level, measured in dB, with 1V / Pa as the reference for 0 dB, so Lx is generally negative.

[0102] The control unit (MCU) controls the DAC unit to generate a 500 Hz / 1 V sine wave signal. This scheme uses second harmonic calibration, and the signal sensed on the microphone diaphragm is a 1 kHz sine wave signal.

[0103] The signal applied to the electrostatic exciter is controlled by an adjustable potentiometer. After the electrostatic excitation signal is applied to the electrostatic excitation plate, the microphone begins to output a corresponding weak signal. This signal is impedance matched by the preamplifier built into the acoustic measurement instrument and then enters the signal conditioning and ADC module of the host computer. The control unit (MCU) then calculates the sound pressure level based on the initial sensitivity level Lx generated by acoustic calibration and displays it on the screen. Feedback from the sound pressure level parameters displayed on the screen allows the adjustable potentiometer to be adjusted to achieve the preset equivalent sound pressure level parameters. Therefore, under the initial parameters of a 500 Hz / 1 V sinusoidal signal generated by the DAC unit, the high-voltage AC signal output after passing through the electrostatic excitation signal generator is the signal that meets the preset equivalent sound pressure level.

[0104] Regarding the selection of the preset equivalent sound pressure level, based on the structure of this scheme, the calibration sound pressure level for electrostatic excitation differs from the acoustic calibration sound pressure level. To achieve a calibration sound pressure level of 94 dB, the electrostatic excitation signal would need to be very large, exceeding the linear range of the sound pressure transformer. Alternatively, the distance 'd' between the electrostatic exciter and the microphone diaphragm could be reduced, but this method is prone to damaging the microphone diaphragm. Therefore, this embodiment uses 90 dB as the electrostatic excitation calibration sound pressure level. The initial electrostatic excitation calibration ends when the reading reaches 90.0 dB. After completing the above operations, when remote calibration is enabled, the electrostatic exciter can output a simulated sound pressure level of 1 kHz / 90 dB. The microphone and acoustic measuring instrument meet the requirements for remote automatic calibration, allowing for timed remote calibration without requiring daily on-site calibration by personnel.

[0105] Figure 5 The method for calibrating a remote microphone includes the following steps:

[0106] Upon receiving a remote calibration command, the initial signal generation unit is activated to generate a sinusoidal signal.

[0107] The sinusoidal signal is processed by the electrostatic excitation signal generation unit and output as a high-voltage AC signal that meets the preset equivalent sound pressure level, and then output to the electrostatic exciter.

[0108] The electrostatic pressure relative to the microphone diaphragm is generated by an electrostatic exciter, and the microphone outputs a corresponding electrical signal.

[0109] The sensitivity level of the microphone is calculated based on the corresponding electrical signal output by the microphone and the preset equivalent sound pressure level.

[0110] Using the acoustic measuring instrument as the main body of the method, when the acoustic measuring instrument's remote communication unit receives a calibration command from the cloud platform or other remote terminal, the control unit (MCU) controls the initial signal generation unit to output a sinusoidal signal matching the calibration frequency; the electrostatic excitation signal generation unit generates a regulated high-voltage AC signal, and the analog signal is not adjusted throughout the process. After the high-voltage AC signal is applied by the electrostatic excitation signal application device, it is connected to the integrated electrostatic exciter and applied to the microphone diaphragm to generate an analog signal with a specified frequency and equivalent sound pressure level. The corresponding weak electrical signal output by the microphone is then connected to the signal conditioning and ADC conversion of the host after impedance transformation of the preamplifier stage, and then input to the control unit MCU. The control unit MCU performs calibration according to the preset equivalent sound pressure level. According to formula (8), the control unit MCU automatically adjusts Lx until Leq(t) is equal to a stable 90.0 dB, then stops the signal output of the DAC unit. The calibration is completed, the new sensitivity level is automatically recorded, and fed back to the cloud platform. This solves the problem of short-term drift of the microphone sensitivity level.

[0111] This solution can also serve as a calibration method for acoustic measuring instruments. The acoustic measuring instrument in this solution includes a microphone, preamplifier (and cables), and main unit (signal conditioning unit + ADC unit). Sensitivity level calibration can simultaneously determine the overall status of the acoustic measuring instrument, including the microphone, preamplifier, main unit, and output interfaces, to ensure it is functioning correctly. Remotely setting up daily scheduled automatic calibration can serve as a quality control measure.

[0112] Based on the differences in sensitivity levels obtained from periodic automatic calibration and the requirements of relevant environmental protection standards, several microphone statuses can be defined. For example, a sensitivity level difference of no more than 0.2 dB between consecutive days is considered excellent, 0.2~0.4 dB is good, 0.4~0.6 dB is acceptable, and greater than 0.6 dB is poor. These results can be submitted to a remote cloud platform through the host's interactive interface to remind maintenance personnel and ensure the accuracy of monitoring data.

[0113] Example 2:

[0114] This embodiment provides an improved electrostatic exciter that can generate a long-term stable static pressure level and a specified frequency on a microphone diaphragm.

[0115] An electrostatic exciter, mounted on a microphone protective cover, such as... Figure 6 ,include:

[0116] Electrostatic excitation board 3-1 is connected to the excitation signal generator;

[0117] The housing fixes the electrostatic excitation plate, which is located at a fixed distance above the microphone diaphragm, forming a relatively effective area with the surface of the microphone diaphragm.

[0118] The distance between the electrostatic excitation plate and the microphone diaphragm remains constant.

[0119] The shell includes:

[0120] The main body of the housing 3-2 has a hollow structure and is used to fix the electrostatic exciter to the microphone;

[0121] The insulating layer 3-3 has a hollow structure and is located on the upper part of the main body of the housing. It is adapted to the periphery of the main body of the housing. An electrostatic excitation plate is installed in the middle of the insulating layer so that the housing and the microphone diaphragm form a relatively effective area after the housing is installed on the microphone diaphragm.

[0122] In this embodiment, the insulating layer is made of epoxy resin board. The electrostatic excitation board has external threads on its outer periphery, and the epoxy resin board has matching internal threads. The electrostatic excitation board is screwed onto the epoxy resin board through its own external threads. The epoxy resin board with the electrostatic excitation board installed is then pressed onto the upper part of the housing body. It can be understood that the hollow part of the housing body is opposite to the electrostatic excitation board. The insulating layer (epoxy resin board) serves both insulation and fixation functions here, and the material exhibits minimal deformation due to temperature and humidity influences. Therefore, any material that meets both the two main functions of minimal deformation and insulation can be used for the insulating layer.

[0123] The housing body is made of the same material as the microphone body to reduce the impact of thermal expansion on the distance between the electrostatic excitation plate and the microphone diaphragm after installation. For noise monitoring instruments that need to be used outdoors for extended periods, P1Cr18Ni9Ti stainless steel is preferred. The housing is screwed onto the microphone protective cover via 3-4 threads.

[0124] As a preferred embodiment, this application also proposes an electrostatic excitation signal application device, wherein one end of the electrostatic excitation signal application device is connected to an electrostatic excitation signal generator and the other end is connected to the electrostatic excitation plate, and a high-voltage AC signal is transmitted to the electrostatic excitation plate through contact with the electrostatic excitation plate.

[0125] As one embodiment, this application discloses a specific electrostatic excitation signal application device, such as... Figure 7 As shown, it includes a wire 2-1 connected to the excitation signal generator, a spring pin 2-2, and an application device housing 2-4. The wire is connected to the spring pin, and the spring pin is in contact with the electrostatic excitation plate 3-1.

[0126] To achieve precise and reliable positioning, a spring pin is welded onto an adapter 2-3, which has an external thread 2-5 and is screwed onto the housing of the application device. The housing of the application device is made of ABS engineering plastic and serves to provide insulation and fixation.

[0127] In this solution, the distance *d* between the electrostatic excitation plate and the microphone diaphragm needs to be fixed. If the spring force of the ejector pin is too large, it will affect the distance *d* between the electrostatic excitation plate and the microphone diaphragm, causing *d* to vary greatly at different temperatures, thus leading to inaccurate electrostatic excitation calibration. This application discloses the selection and installation requirements of an ejector pin, using a spring ejector pin with a contact spring force of 70g-100g. Since the spring force of the spring ejector pin is related to the stroke, the stroke of the spring ejector pin is controlled to be at 1 / 3 of the total stroke after contact with the electrostatic excitation plate. The above parameters are for reference only; in actual product applications, adaptive adjustments need to be made according to different types and sizes of microphones.

[0128] The electrostatic excitation signal is applied to an electrostatic excitation board integrated on the microphone, providing a stable, low-distortion static pressure to the microphone. The entire circuit is simple, uses few components, and can be easily applied to acoustic measuring instruments such as handheld sound level meters and automatic environmental noise monitoring instruments.

[0129] The specific parameters disclosed in Examples 1 and 2 are all reference values ​​for better understanding of this solution and are not intended to limit it. Furthermore, the "connection" described in this application includes both direct and indirect connections.

[0130] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules or units is merely a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another apparatus, or some features may be ignored or not executed.

[0131] The units may or may not be physically separate. The components shown as units can be one or more physical units, meaning they can be located in one place or distributed in multiple different locations. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0132] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0133] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solution of the embodiments of the present invention, essentially, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0134] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A remote microphone calibration apparatus, characterized by, The application relates to a remote microphone calibration device, which comprises the following parts: an initial signal generating unit for outputting a sine signal matched with a calibration frequency; an electrostatic excitation signal generating unit electrically connected with the initial signal generating unit, receiving the sine signal output by the initial signal generating unit, processing and outputting a high-voltage alternating current signal meeting a preset equivalent sound pressure level; an electrostatic exciter electrically connected with the electrostatic excitation signal generating device; the electrostatic exciter is installed above a microphone diaphragm at a fixed distance and forms a relative effective area with the surface of the microphone diaphragm, the electrostatic exciter receives the high-voltage alternating current signal and generates static pressure relative to the microphone diaphragm; a control unit for receiving a remote calibration instruction and starting the initial signal generating unit; wherein the preset equivalent sound pressure level is calculated according to the initial sensitivity level of the microphone under the action of an acoustic calibrator, and the calibration frequency is the standard frequency of the acoustic calibrator; the electrostatic excitation signal generating unit comprises the following structures: a direct current eliminating unit for eliminating the fundamental frequency signal of the sine signal, the input end of the direct current eliminating unit is connected with the initial signal generating unit and receives the sine signal matched with the initial calibration frequency; a voltage adjusting unit for adjusting voltage so that the high-voltage alternating current signal output by a voltage boosting unit meets the preset equivalent sound pressure level; a signal amplifying unit connected with the voltage adjusting unit and performing primary amplification on the sine alternating current signal; a voltage boosting unit connected with the signal amplifying unit and used for boosting the sine alternating current signal to a high-voltage alternating current signal, wherein the output high-voltage alternating current signal meets the preset equivalent sound pressure level; the method for calculating the preset equivalent sound pressure level according to the initial sensitivity level of the microphone under the action of the acoustic calibrator comprises the following steps: initial calibration of the microphone is performed by using the acoustic calibrator to generate the initial sensitivity level Lx; the electrostatic excitation signal is obtained through the electrostatic excitation signal generating unit, and the electrostatic excitation signal output by the electrostatic excitation signal generating unit is adjusted according to the initial sensitivity level so that the electrostatic excitation signal meets the preset calibration sound pressure level when acting on the electrostatic exciter; 2. A remote microphone calibration apparatus according to claim 1, wherein, the electrostatic excitation signal meeting the preset calibration sound pressure level requirement is saved. The electrostatic exciter comprises: an electrostatic excitation plate; a shell for fixing the electrostatic excitation plate, wherein the electrostatic excitation plate is located above the microphone diaphragm at a fixed distance and forms a relative effective area with the surface of the microphone diaphragm; 3. A remote microphone calibration apparatus as claimed in claim 1 or 2, wherein, the distance between the electrostatic excitation plate and the microphone diaphragm is fixed and unchangeable. The application further comprises:

4. A remote microphone calibration apparatus as claimed in claim 1, wherein, an electrostatic excitation signal applying device, one end of the electrostatic excitation signal applying device is electrically connected with the electrostatic excitation signal generating unit, and the other end of the electrostatic excitation signal applying device is electrically connected with the electrostatic exciter, thereby applying the high-voltage alternating current signal to the electrostatic exciter through contact.

5. An acoustic measuring instrument, characterized in that The sine signal matched with the calibration frequency is 1 / 2 of the standard frequency of the acoustic calibrator.

6. A method of remotely calibrating a microphone, the method comprising: The remote microphone calibration device comprises a microphone, a preamplifier, a host computer and a remote interaction interface. The remote microphone calibration device is used in the following steps: a remote calibration instruction is received, and the initial signal generating unit generates a sine signal; the sine signal is processed and output to the electrostatic exciter through the electrostatic excitation signal generating unit, so that a high-voltage alternating current signal meeting a preset equivalent sound pressure level is output; static pressure relative to the microphone diaphragm is generated through the electrostatic exciter, and the microphone outputs a corresponding electric signal; According to the electric signal, preset equivalent sound pressure level calculates the sensitivity level of current microphone.

7. A method of remotely calibrating a microphone as claimed in claim 6, wherein, The method for adjusting the electrostatic excitation signal output by the electrostatic excitation signal generating unit according to the initial sensitivity level so that the electrostatic excitation signal reaches the preset calibration sound pressure level, comprising the steps of: The initial signal generating unit generates a sine signal satisfying the 1 / 2 sound calibration frequency, and the initial electrostatic excitation signal is output to the electrostatic excitation device through the electrostatic excitation signal generating unit; The control unit calculates the current equivalent sound pressure level according to the microphone signal obtained under the action of the initial electrostatic excitation signal and the initial sensitivity level Lx, and displays it, and adjusts the electrostatic excitation signal according to the current equivalent sound pressure level parameter until the current equivalent sound pressure level reaches the preset equivalent sound pressure level.

8. A method of calibrating an acoustic measuring instrument, characterized by, The step comprises a remote microphone calibration method according to claim 6 or 7.

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