Intrinsic safety type negative feedback sound calibration system

Abstract

The invention discloses an intrinsic safety type negative feedback sound calibration system, and relates to the field of acoustic measurement. According to the specific implementation scheme, the system comprises an MCU module, a data acquisition module, a signal generation module, an interaction module and a power supply module, the data acquisition module is used for feeding back the collected data information to the MCU module; the MCU module is used for generating a pure tone signal, calculating a sound pressure level based on the data information collected by the data acquisition module, and adjusting the amplitude of signal output; the signal generation module is used for performing digital-to-analog conversion on the to-be-output signal generated by the MCU module, and then amplifying the amplitude and power of the signal through a power amplifier so as to drive a loudspeaker LS1 to produce sound; the interaction module is used for interacting with the external environment according to the indication of the MCU module; the power module is used for supplying power to the whole system. The microphone is used as a feedback sensor, the precision of generated sound signals is high, the capability of resisting the influence of environmental temperature and humidity is high, and the electret microphone is used as the feedback sensor, so that the maximum voltage required by the circuit design is greatly reduced.

Description

Technical Field

[0001] The present application relates to the technical field of acoustic measurement, and in particular to an intrinsically safe negative feedback acoustic calibration system. Background Art

[0002] As modern noise pollution becomes more and more serious, the country is paying more and more attention to the prevention and control of noise. As a special noise measurement instrument, the sound level meter is increasingly used in environmental noise in various occasions such as industrial enterprises, construction, airports, and social life. Usually, this type of acoustic measurement instrument will be equipped with a microphone to convert the sound signal into an electrical signal. There are many types of microphones. Before each measurement, the microphone of the measuring instrument needs to be calibrated with an acoustic calibrator to obtain the sensitivity of the microphone in order to achieve accurate measurement of the noise sound pressure level.

[0003] The sensitivity detection of microphone is mainly realized by sound calibrator. At present, there are many sound calibrator manufacturers at home and abroad, and there are many types. The sound signals emitted by these sound calibrators have low accuracy and are applicable to a narrow range of ambient temperature and humidity. They are limited to daily use and cannot meet the requirements of intrinsic safety. Summary of the invention

[0004] Based on this, the present application provides an intrinsically safe negative feedback sound calibration system to solve the problem of low accuracy of the sound signal emitted by the sound calibrator.

[0005] The present application provides an intrinsically safe negative feedback sound calibration system, comprising:

[0006] MCU module, data acquisition module, signal generation module, interaction module and power module;

[0007] The data acquisition module is used to feed back the collected data information to the MCU module;

[0008] The MCU module is used to generate a pure tone signal, calculate the sound pressure level based on the data information collected by the data acquisition module, and adjust the amplitude of the signal output according to the sound pressure level;

[0009] The signal generating module is used to convert the signal to be output generated by the MCU module into digital-to-analog form, and then amplify the amplitude and power of the signal through the power amplifier to drive the speaker LS1 to produce sound;

[0010] The interaction module is used to interact with the external environment according to the instruction of the MCU module;

[0011] The power module is used to supply power to the entire system.

[0012] The power module includes a battery pack BT1, a fuse F1, a resistor R43 and an equivalent load RL. The positive pole of the battery pack BT1 is connected to a +3V power supply, the negative pole of the battery pack BT1 is grounded, one end of the fuse F1 is connected to the positive pole of the battery pack BT1, and the other end of the fuse F1 is electrically connected to one end of the equivalent load RL through the resistor R43, and the other end of the equivalent load RL is connected to the negative pole of the battery pack BT1.

[0013] The power module provides 3.3V and 5V power to the system after passing through the LDO and DC-DC circuits.

[0014] The data acquisition module includes an electret microphone M1 and a preamplifier circuit. The preamplifier circuit is a field effect transistor follower and is used to optimize the output impedance of the electret microphone M1.

[0015] One end of the electret microphone M1 is electrically connected to pin No. 3 of the MOS tube Q1, the other end of the electret microphone M1 is grounded, the resistor R1 and the resistor R2 are connected in series, the voltage source VD is grounded through the resistor R1 and the resistor R2, a detection point A is arranged between the resistor R1 and the resistor R2, one end of the resistor R3 is electrically connected to the detection point A, the other end of the resistor R3 is electrically connected to pin No. 3 of the MOS tube Q1, pin No. 2 of the MOS tube Q1 is connected to the voltage source VD, pin No. 1 of the MOS tube Q1 is grounded through the resistor R4, a detection point S is arranged at pin No. 1 of the MOS tube Q1, one end of the capacitor C1 is connected to the detection point S, and the other end of the capacitor C1 is connected to the MCU module.

[0016] The MCU module includes a main control chip U2, a crystal oscillator Y1, an inductor L1, a diode D1, a light-emitting diode D2 and a light-emitting diode D3;

[0017] Pin 5 and pin 6 of the main control chip U2 are respectively connected to the two ends of the crystal oscillator Y1, pin 5 of the main control chip U2 is also grounded through a capacitor C5, pin 6 of the main control chip U2 is also grounded through a capacitor C6, pin 6 of the main control chip U2 is also connected to pin 8 of the main control chip U2 through capacitor C6, pin 8 of the main control chip U2 is also electrically connected to one end of a resistor R16, the other end of the resistor R16 is electrically connected to pin 13 of the main control chip U2, and the resistor R16 The other end of the inductor L1 is also connected to the power supply voltage VCC through the resistor R19, the capacitor C14 is connected in parallel with the resistor R16, one end of the inductor L1 is electrically connected to the pin 9 of the main control chip U2, the other end of the inductor L1 is electrically connected to the pin 48 of the main control chip U2, one end of the inductor L1 is also electrically connected to one end of the resistor R16 through the capacitor C9, the other end of the inductor L1 is also electrically connected to one end of the resistor R16 through the capacitor C10, and the pins 39, 40, 41, 42, and 43 of the main control chip U2 are respectively The 5th, 4th, 3rd, 2nd and 1st pins of the switch S1 are electrically connected respectively, the 6th, 7th, 8th, 9th and 10th pins of the switch S1 are all connected to one end of the capacitor C1, the other end of the capacitor C1 is electrically connected to the 48th pin of the main control chip U2, the capacitor C2 and the capacitor C3 are all connected in parallel with the capacitor C1, the 48th pin of the main control chip U2 is electrically connected to the 1st pin of the main control chip U2 through the diode D1, the 1st pin of the main control chip U2 is also grounded through the capacitor C5, the +3.3V power supply is connected to the light emitting diode D 2. Resistor R7 is connected in sequence and then electrically connected to pin 30 of the main control chip U2. The +3.3V power supply is connected to the light-emitting diode D3 and the resistor R10 in sequence and then electrically connected to pin 29 of the main control chip U2. The +3.3V power supply is also electrically connected to pin 33 of the main control chip U2 through resistor R5. The positive electrode interface D+ of the USB is electrically connected to pin 33 of the main control chip U2 through resistor R6, and the negative electrode interface D- of the USB is electrically connected to pin 32 of the main control chip U2 through resistor R8.

[0018] The signal generating module comprises an audio power amplifier U3 and a speaker LS1, wherein pin 1 of the audio power amplifier U3 is connected to a +5V power supply, one end of a capacitor C7 is electrically connected to pin 14 of the main control chip U2 via a resistor R12, one end of the capacitor C7 is also grounded via a capacitor C16, the other end of the capacitor C7 is electrically connected to pin 2 of the audio power amplifier U3, pin 3 of the audio power amplifier U3 is grounded via a resistor R17, pin 4 of the audio power amplifier U3 is electrically connected to pin 16 of the main control chip U2 via a resistor R14, and pin 4 of the audio power amplifier U3 is electrically connected to pin 16 of the main control chip U2. The pin is also grounded through capacitor C15, pin 5 of the audio power amplifier U3 is electrically connected to one end of the speaker LS1 through resistor R15, pin 8 of the audio power amplifier U3 is electrically connected to the other end of the speaker LS1 through resistor R11, capacitor C13 is connected to both ends of the speaker LS1, pin 7 of the audio power amplifier U3 is grounded through capacitor C11, pin 6 of the audio power amplifier U3 is grounded, one end of resistor R18 is electrically connected to pin 5 of the audio power amplifier U3, and the other end of resistor R18 is electrically connected to pin 21 of the main control chip U2.

[0019] The data acquisition module uses the sound calibrator to generate a pure tone signal of 1000Hz, 94dB / 114dB, outputs an analog signal through the built-in DAC of the MCU module, and the pure tone signal is emitted by the speaker LS1 after passing through the power amplifier. The calculation of signal generation includes:

[0020]

[0021] Among them, data[i] represents the sine signal array, i represents the pointer of the sine signal array, amp represents the sine signal amplification factor, 80 represents the number of samples in one cycle, and 32768 represents the median value of the DAC output;

[0022] The sound calibrator outputs the collected data information to the MCU module through the electret microphone M1 and the pre-stage circuit, and converts the data information into a digital signal using the built-in ADC of the MCU module.

[0023] Also includes,

[0024] The MCU module sets the sampling frequency through the timer, sets the ADC sampling frequency to 512Hz, and performs a fast Fourier transform operation by sampling 1024 points;

[0025] result=(x[i] 2 +x[fft len -i] 2 )÷fft len ;

[0026] Among them, result represents the amplitude of the Fourier transform operation result, x[i]-the i-th data value collected, fft len Indicates the amount of data in the collected array;

[0027] Adjust the output sound pressure level based on the target output and feedback output.

[0028]

[0029] Among them, amp represents the amplification factor of the sinusoidal signal before adjustment, amp′ represents the amplification factor of the sinusoidal signal after adjustment, norm_p represents the effective value of the collected sinusoidal signal, and sound_p represents the effective value of the target sinusoidal signal;

[0030] when Stop automatic adjustment.

[0031] The interactive module includes a button and a status indicator light circuit, wherein the button is used for turning on and off the machine and selecting the sound pressure level of the calibration signal, and the indicator light is used for indicating the current working status of the calibrator.

[0032] Beneficial effects: The present invention adopts a microphone as a feedback sensor, generates a sound signal with high accuracy, and has a strong ability to resist the influence of environmental temperature and humidity. The electret microphone is used as a feedback sensor, which greatly reduces the maximum voltage required for circuit design.

[0033] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are used to better understand the present solution and do not constitute a limitation of the present application.

[0035] Figure 1 It is a system principle block diagram provided according to this application;

[0036] Figure 2 is an equivalent circuit diagram of a power module provided according to the present application;

[0037] Figure 3 It is a circuit schematic diagram of a data acquisition module provided in this application;

[0038] Figure 4 It is a circuit schematic diagram of the MCU module provided in this application;

[0039] Figure 5 This is a circuit schematic diagram of a signal generating module provided in this application. DETAILED DESCRIPTION

[0040] The following is a description of exemplary embodiments of the present application in conjunction with the accompanying drawings, including various details of the embodiments of the present application to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, the description of well-known functions and structures is omitted in the following description.

[0041] like Figure 1 As shown, the present application provides an intrinsically safe negative feedback sound calibration system, comprising:

[0042] MCU module, data acquisition module, signal generation module, interaction module and power module;

[0043] The data acquisition module is used to feed back the collected data information to the MCU module;

[0044] The MCU module is used to generate a pure tone signal, calculate the sound pressure level based on the data information collected by the data acquisition module, and adjust the amplitude of the signal output according to the sound pressure level;

[0045] The signal generating module is used to convert the signal to be output generated by the MCU module into digital-to-analog form, and then amplify the amplitude and power of the signal through the power amplifier to drive the speaker LS1 to produce sound;

[0046] The interaction module is used to interact with the external environment according to the instruction of the MCU module;

[0047] The power module is used to supply power to the entire system.

[0048] The power module includes a battery pack BT1, a fuse F1, a resistor R43 and an equivalent load RL. The positive pole of the battery pack BT1 is connected to a +3V power supply, the negative pole of the battery pack BT1 is grounded, one end of the fuse F1 is connected to the positive pole of the battery pack BT1, and the other end of the fuse F1 is electrically connected to one end of the equivalent load RL through the resistor R43, and the other end of the equivalent load RL is connected to the negative pole of the battery pack BT1.

[0049] The power module provides 3.3V and 5V power to the system after passing through the LDO and DC-DC circuits.

[0050] Furthermore, the whole machine is powered by two No. 5 batteries. After passing through LDO (low dropout linear regulator) and DC-DC circuit (a circuit that converts a fixed DC voltage into another fixed or variable DC voltage), the system provides 3.3V and 5V power. In this circuit, the battery pack BT1 is connected in series with a 0.25A fuse F1 and a 3Ω resistor R43. Its equivalent circuit is as follows: Figure 2As shown, the melting heat energy of the blown fuse F1 is 0.00042A2Sec. The nominal cold resistance of the fuse F1 is 3.25Ω, and a 3Ω resistor R43 is connected in series to form a current limiting resistor.

[0051] The electrical parameters of the equivalent power circuit composed of battery pack BT1, fuse F1, and current limiting resistor are: open circuit voltage: 3.46V, internal resistance 7.25Ω. RL is the equivalent load of the power circuit. When the equivalent load RL matches the equivalent internal resistance 7.25Ω, the equivalent power circuit outputs the maximum power and the load obtains the maximum power, which is about 0.414W. At this time, the power of fuse F1 is 0.185W, and the power of the current limiting resistor is 0.170W, which meets the provisions of GB3836.4-2021 5.6.2 Small component temperature table 2a) and b) for the maximum power dissipation of small components of Class II instruments at 50℃.

[0052] In extreme cases, when the equivalent load RL is short-circuited, the circuit is resistive, and its maximum short-circuit current is 3.46V / (3.25+3+1.002)Ω≈0.477A. ​​After applying a safety factor of 1.5, the current is about 0.716A. According to Appendix A of the document GB3836.4-2021, for the IIB resistive circuit, 3.46V-0.716A meets the requirements of Figure A.1. When the load is short-circuited, the fusing time of the fuse is 0.00042 / (0.477)2≈1.85ms. In summary, the circuit is intrinsically safe.

[0053] The data acquisition module includes an electret microphone M1 and a preamplifier circuit. The preamplifier circuit is a field effect transistor follower for optimizing the output impedance of the electret microphone M1. The circuit schematic diagram is shown in FIG. Figure 3 shown.

[0054] The present invention selects AWA14426 type electret microphone as the core component of the feedback unit.

[0055] One end of the electret microphone M1 is electrically connected to pin No. 3 of the MOS tube Q1, the other end of the electret microphone M1 is grounded, the resistor R1 and the resistor R2 are connected in series, the voltage source VD is grounded through the resistor R1 and the resistor R2, a detection point A is arranged between the resistor R1 and the resistor R2, one end of the resistor R3 is electrically connected to the detection point A, the other end of the resistor R3 is electrically connected to pin No. 3 of the MOS tube Q1, pin No. 2 of the MOS tube Q1 is connected to the voltage source VD, pin No. 1 of the MOS tube Q1 is grounded through the resistor R4, a detection point S is arranged at pin No. 1 of the MOS tube Q1, one end of the capacitor C1 is connected to the detection point S, and the other end of the capacitor C1 is connected to the MCU module.

[0056] Among them, the static voltage at point A is:

[0057]

[0058] Among them, V AQ Represents the static voltage at point A, V DQ Indicates the static voltage at point VD;

[0059] Static voltage at point S:

[0060] V SQ =I DQ ×R4 (2)

[0061] Among them, V SQ Represents the static voltage at point S, I DQ Indicates the static current at point VD;

[0062] To ensure that the above preamplifier circuit has the widest voltage range, adjust the resistance value of R4 so that V SQ Approx.

[0063] Input resistance R in :

[0064]

[0065] Output resistance R O :

[0066]

[0067] Among them, g m It represents the rate of change of input admittance with respect to output current and can be found by consulting the characteristic diagram of the selected transistor;

[0068] Magnification:

[0069]

[0070] When m ×R4>>1, magnification A u ≈1.

[0071] like Figure 4 As shown, the MCU module includes a main control chip U2, a crystal oscillator Y1, an inductor L1, a diode D1, a light-emitting diode D2 and a light-emitting diode D3;

[0072] Pin 5 and pin 6 of the main control chip U2 are respectively connected to the two ends of the crystal oscillator Y1, pin 5 of the main control chip U2 is also grounded through a capacitor C5, pin 6 of the main control chip U2 is also grounded through a capacitor C6, pin 6 of the main control chip U2 is also connected to pin 8 of the main control chip U2 through capacitor C6, pin 8 of the main control chip U2 is also electrically connected to one end of a resistor R16, the other end of the resistor R16 is electrically connected to pin 13 of the main control chip U2, and the resistor R16 The other end of the inductor L1 is also connected to the power supply voltage VCC through the resistor R19, the capacitor C14 is connected in parallel with the resistor R16, one end of the inductor L1 is electrically connected to the pin 9 of the main control chip U2, the other end of the inductor L1 is electrically connected to the pin 48 of the main control chip U2, one end of the inductor L1 is also electrically connected to one end of the resistor R16 through the capacitor C9, the other end of the inductor L1 is also electrically connected to one end of the resistor R16 through the capacitor C10, and the pins 39, 40, 41, 42, and 43 of the main control chip U2 are respectively The 5th, 4th, 3rd, 2nd and 1st pins of the switch S1 are electrically connected respectively, the 6th, 7th, 8th, 9th and 10th pins of the switch S1 are all connected to one end of the capacitor C1, the other end of the capacitor C1 is electrically connected to the 48th pin of the main control chip U2, the capacitor C2 and the capacitor C3 are all connected in parallel with the capacitor C1, the 48th pin of the main control chip U2 is electrically connected to the 1st pin of the main control chip U2 through the diode D1, the 1st pin of the main control chip U2 is also grounded through the capacitor C5, the +3.3V power supply is connected to the light emitting diode D 2. Resistor R7 is connected in sequence and then electrically connected to pin 30 of the main control chip U2. The +3.3V power supply is connected to the light-emitting diode D3 and the resistor R10 in sequence and then electrically connected to pin 29 of the main control chip U2. The +3.3V power supply is also electrically connected to pin 33 of the main control chip U2 through resistor R5. The positive electrode interface D+ of the USB is electrically connected to pin 33 of the main control chip U2 through resistor R6, and the negative electrode interface D- of the USB is electrically connected to pin 32 of the main control chip U2 through resistor R8.

[0073] Furthermore, the main control chip U2 adopts the STM32F373 chip. The STM32F3 series microcontroller integrates a 32-bit ARM Cortex-M4 core with DSP and FPU instructions, an operating frequency of 72MHz, and advanced analog peripherals, thereby improving flexibility.

[0074] The MCU module is used to generate pure tone signals and calculate the sound pressure level of the feedback signal collected by the data acquisition circuit, so as to adjust the amplitude of the signal output and control the size of the sound emitted by the speaker, thereby realizing closed-loop control of the sound pressure level in the sound cavity.

[0075] The MCU module sets the sampling frequency through the timer, sets the ADC (analog-to-digital converter) sampling frequency to 512Hz, samples 1024 points (i.e., samples for 2 seconds) and performs an FFT (fast Fourier transform) operation to make the frequency domain resolution reach 0.5Hz. The Fourier sequence is obtained by using FFT, and the amplitude-frequency characteristic sequence is obtained by calculating it. The sound pressure level of the current pure tone signal can be calculated by selecting the amplitude of the required frequency (1kHz or 250Hz). At the same time, the Fourier transform can eliminate the interference of other frequency sound signals, thereby improving the anti-interference ability of the sound calibrator.

[0076] like Figure 5 As shown, the signal generating module includes an audio power amplifier U3 and a speaker LS1. Pin 1 of the audio power amplifier U3 is connected to a +5V power supply, one end of a capacitor C7 is electrically connected to pin 14 of the main control chip U2 through a resistor R12, one end of the capacitor C7 is also grounded through a capacitor C16, the other end of the capacitor C7 is electrically connected to pin 2 of the audio power amplifier U3, pin 3 of the audio power amplifier U3 is grounded through a resistor R17, pin 4 of the audio power amplifier U3 is electrically connected to pin 16 of the main control chip U2 through a resistor R14, and pin 4 of the audio power amplifier U3 is electrically connected to pin 16 of the main control chip U2. Pin No. 5 of the audio power amplifier U3 is also grounded through capacitor C15, pin No. 5 of the audio power amplifier U3 is electrically connected to one end of the speaker LS1 through resistor R15, pin No. 8 of the audio power amplifier U3 is electrically connected to the other end of the speaker LS1 through resistor R11, capacitor C13 is connected to both ends of the speaker LS1, pin No. 7 of the audio power amplifier U3 is grounded through capacitor C11, pin No. 6 of the audio power amplifier U3 is grounded, one end of resistor R18 is electrically connected to pin No. 5 of the audio power amplifier U3, and the other end of resistor R18 is electrically connected to pin No. 21 of the main control chip U2.

[0077] Figure 5Pin 3 of LM4875 is the detection pin, and pin 2 is connected to MCU to receive the pure sound signal output from MCU. The 10kΩ resistor R12 is connected in series to increase the input impedance, and the 10μF capacitor is connected in series to isolate the DC component. Pin 4 is the DC input, which is used to control the gain of LM4875. A passive low-pass filter is built between the voltage signal output by MCU and LM4875 using R14 and C15 to make the voltage of pin 4 more stable and improve the anti-interference ability. R11 and R15 in the figure are impedance matching resistors, which are used to increase the output impedance of LM4875 and limit the output power. A 1μF capacitor is connected in parallel at the output end of the speaker to achieve the purpose of reducing distortion. A resistor voltage divider is connected to pin 5, which is connected to the ADC peripheral of MCU through the network MIC0. When there is no microphone inserted in the calibrator, the speaker will continue to increase the output sound pressure level. When the sound pressure level exceeds the limit, it will be judged that the microphone is not inserted and the shutdown command will be executed to achieve automatic shutdown, reduce power consumption, and increase battery life.

[0078] The data acquisition module uses the sound calibrator to generate a pure tone signal of 1000Hz, 94dB / 114dB, outputs an analog signal through the built-in DAC (digital-to-analog converter) of the MCU module, and the pure tone signal is emitted by the speaker LS1 after passing through the power amplifier. The calculation of signal generation includes:

[0079]

[0080] Among them, data[i] represents the sine signal array, i represents the pointer of the sine signal array, amp represents the sine signal amplification factor, 80 represents the number of samples in one cycle, and 32768 represents the median value of the DAC output;

[0081] The data acquisition module selects LM4875 as the audio power amplifier to achieve high efficiency, low power consumption, low distortion and low noise.

[0082] The sound calibrator outputs the collected data information to the MCU module through the electret microphone M1 and the pre-stage circuit, and converts the data information into a digital signal using the built-in ADC of the MCU module.

[0083] Also includes,

[0084] The MCU module sets the sampling frequency through the timer, sets the ADC sampling frequency to 512Hz, and performs a fast Fourier transform operation by sampling 1024 points;

[0085] result=(x[i] 2 +x[fft len -i] 2 )÷fft len ;

[0086] Among them, result represents the amplitude of the Fourier transform operation result, x[i]-the i-th data value collected, fft len Indicates the amount of data in the collected array;

[0087] Adjust the output sound pressure level based on the target output and feedback output.

[0088]

[0089] Among them, amp represents the amplification factor of the sinusoidal signal before adjustment, amp′ represents the amplification factor of the sinusoidal signal after adjustment, norm_p represents the effective value of the collected sinusoidal signal, and sound_p represents the effective value of the target sinusoidal signal;

[0090] when Stop automatic adjustment.

[0091] The interactive module includes a button and a status indicator light circuit, wherein the button is used for turning on and off the machine and selecting the sound pressure level of the calibration signal, and the indicator light is used for indicating the current working status of the calibrator.

[0092] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed.

[0093] The units may or may not be physically separated, and the components displayed as units may be one physical unit or multiple physical units, that is, they may be located in one place or distributed in multiple different places. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0094] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0095] If the integrated unit is implemented in the form of 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 embodiment of the present invention is 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, which is stored in a storage medium and includes several instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor (processor) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), disk or optical disk and other media that can store program codes.

[0096] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An intrinsically safe negative feedback acoustic calibration system, characterized in that: include: MCU module, data acquisition module, signal generation module, interaction module and power module; The data acquisition module is used to feed back the collected data information to the MCU module; The MCU module is used to generate a pure tone signal, calculate the sound pressure level based on the data information collected by the data acquisition module, and adjust the amplitude of the signal output according to the sound pressure level; The signal generating module is used to convert the signal to be output generated by the MCU module into digital-to-analog form, and then amplify the amplitude and power of the signal through the power amplifier to drive the speaker LS1 to produce sound; The interaction module is used to interact with the external environment according to the instruction of the MCU module; The power module is used to supply power to the entire system.

2. The intrinsically safe negative feedback acoustic calibration system according to claim 1, characterized in that: The power module includes a battery pack BT1, a fuse F1, a resistor R43 and an equivalent load RL. The positive pole of the battery pack BT1 is connected to a +3V power supply, the negative pole of the battery pack BT1 is grounded, one end of the fuse F1 is connected to the positive pole of the battery pack BT1, and the other end of the fuse F1 is electrically connected to one end of the equivalent load RL through the resistor R43, and the other end of the equivalent load RL is connected to the negative pole of the battery pack BT1.

3. The intrinsically safe negative feedback acoustic calibration system according to claim 2, characterized in that: The power module provides 3.3V and 5V power to the system after passing through the LDO and DC-DC circuits.

4. The intrinsically safe negative feedback acoustic calibration system according to claim 3, characterized in that: The data acquisition module includes an electret microphone M1 and a preamplifier circuit. The preamplifier circuit is a field effect transistor follower and is used to optimize the output impedance of the electret microphone M1.

5. An intrinsically safe negative feedback acoustic calibration system according to any one of claims 1 to 4, characterized in that: One end of the electret microphone M1 is electrically connected to pin No. 3 of the MOS tube Q1, the other end of the electret microphone M1 is grounded, the resistor R1 and the resistor R2 are connected in series, the voltage source VD is grounded through the resistor R1 and the resistor R2, a detection point A is arranged between the resistor R1 and the resistor R2, one end of the resistor R3 is electrically connected to the detection point A, the other end of the resistor R3 is electrically connected to pin No. 3 of the MOS tube Q1, pin No. 2 of the MOS tube Q1 is connected to the voltage source VD, pin No. 1 of the MOS tube Q1 is grounded through the resistor R4, a detection point S is arranged at pin No. 1 of the MOS tube Q1, one end of the capacitor C1 is connected to the detection point S, and the other end of the capacitor C1 is connected to the MCU module.

6. The intrinsically safe negative feedback acoustic calibration system according to claim 5, characterized in that: The MCU module includes a main control chip U2, a crystal oscillator Y1, an inductor L1, a diode D1, a light-emitting diode D2 and a light-emitting diode D3; Pin 5 and pin 6 of the main control chip U2 are respectively connected to the two ends of the crystal oscillator Y1, pin 5 of the main control chip U2 is also grounded through a capacitor C5, pin 6 of the main control chip U2 is also grounded through a capacitor C6, pin 6 of the main control chip U2 is also connected to pin 8 of the main control chip U2 through capacitor C6, pin 8 of the main control chip U2 is also electrically connected to one end of a resistor R16, the other end of the resistor R16 is electrically connected to pin 13 of the main control chip U2, and the resistor R16 The other end of the inductor L1 is also connected to the power supply voltage VCC through the resistor R19, the capacitor C14 is connected in parallel with the resistor R16, one end of the inductor L1 is electrically connected to the pin 9 of the main control chip U2, the other end of the inductor L1 is electrically connected to the pin 48 of the main control chip U2, one end of the inductor L1 is also electrically connected to one end of the resistor R16 through the capacitor C9, the other end of the inductor L1 is also electrically connected to one end of the resistor R16 through the capacitor C10, and the pins 39, 40, 41, 42, and 43 of the main control chip U2 are respectively The 5th, 4th, 3rd, 2nd and 1st pins of the switch S1 are electrically connected respectively, the 6th, 7th, 8th, 9th and 10th pins of the switch S1 are all connected to one end of the capacitor C1, the other end of the capacitor C1 is electrically connected to the 48th pin of the main control chip U2, the capacitor C2 and the capacitor C3 are all connected in parallel with the capacitor C1, the 48th pin of the main control chip U2 is electrically connected to the 1st pin of the main control chip U2 through the diode D1, the 1st pin of the main control chip U2 is also grounded through the capacitor C5, the +3.3V power supply is connected to the light emitting diode D 2. Resistor R7 is connected in sequence and then electrically connected to pin 30 of the main control chip U2. The +3.3V power supply is connected to the light-emitting diode D3 and the resistor R10 in sequence and then electrically connected to pin 29 of the main control chip U2. The +3.3V power supply is also electrically connected to pin 33 of the main control chip U2 through resistor R5. The positive electrode interface D+ of the USB is electrically connected to pin 33 of the main control chip U2 through resistor R6, and the negative electrode interface D- of the USB is electrically connected to pin 32 of the main control chip U2 through resistor R8.

7. The intrinsically safe negative feedback acoustic calibration system according to claim 6, characterized in that: The signal generating module comprises an audio power amplifier U3 and a speaker LS1, wherein pin 1 of the audio power amplifier U3 is connected to a +5V power supply, one end of a capacitor C7 is electrically connected to pin 14 of the main control chip U2 via a resistor R12, one end of the capacitor C7 is also grounded via a capacitor C16, the other end of the capacitor C7 is electrically connected to pin 2 of the audio power amplifier U3, pin 3 of the audio power amplifier U3 is grounded via a resistor R17, pin 4 of the audio power amplifier U3 is electrically connected to pin 16 of the main control chip U2 via a resistor R14, and pin 4 of the audio power amplifier U3 is electrically connected to pin 16 of the main control chip U2. The pin is also grounded through capacitor C15, pin 5 of the audio power amplifier U3 is electrically connected to one end of the speaker LS1 through resistor R15, pin 8 of the audio power amplifier U3 is electrically connected to the other end of the speaker LS1 through resistor R11, capacitor C13 is connected to both ends of the speaker LS1, pin 7 of the audio power amplifier U3 is grounded through capacitor C11, pin 6 of the audio power amplifier U3 is grounded, one end of resistor R18 is electrically connected to pin 5 of the audio power amplifier U3, and the other end of resistor R18 is electrically connected to pin 21 of the main control chip U2.

8. The intrinsically safe negative feedback acoustic calibration system according to claim 7, characterized in that: The data acquisition module uses the sound calibrator to generate a pure tone signal of 1000Hz, 94dB / 114dB, outputs an analog signal through the built-in DAC of the MCU module, and the pure tone signal is emitted by the speaker LS1 after passing through the power amplifier. The calculation of signal generation includes: Among them, data[i] represents the sine signal array, i represents the pointer of the sine signal array, amp represents the sine signal amplification factor, 80 represents the number of samples in one cycle, and 32768 represents the median value of the DAC output; The sound calibrator outputs the collected data information to the MCU module through the electret microphone M1 and the pre-stage circuit, and converts the data information into a digital signal using the built-in ADC of the MCU module.

9. The intrinsically safe negative feedback acoustic calibration system according to claim 8, characterized in that: Also includes, The MCU module sets the sampling frequency through the timer, sets the ADC sampling frequency to 512Hz, and performs a fast Fourier transform operation by sampling 1024 points; result=(x[i] 2 +x[fft len -i] 2 )÷fft len ; Among them, result represents the amplitude of the Fourier transform operation result, x[i]-the i-th data value collected, fft len Indicates the amount of data in the collected array; Adjust the output sound pressure level based on the target output and feedback output. Among them, amp represents the amplification factor of the sinusoidal signal before adjustment, amp′ represents the amplification factor of the sinusoidal signal after adjustment, norm_p represents the effective value of the collected sinusoidal signal, and sound_p represents the effective value of the target sinusoidal signal; when Stop automatic adjustment.

10. The intrinsically safe negative feedback acoustic calibration system according to claim 9, characterized in that: The interactive module includes a button and a status indicator light circuit, wherein the button is used for turning on and off the machine and selecting the sound pressure level of the calibration signal, and the indicator light is used for indicating the current working status of the calibrator.

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