A multifunctional calibration device and control method for acoustic calibration

Abstract

The present invention discloses a multifunctional calibration device for sound calibration, including an audio data acquisition and playback module, a gain control module, an acoustic signal output module and an MCU control module; and also discloses a control method including: S1, system hardware initialization and reading stored calibration information; S2, judging whether there is a pre-calibration instruction, if so, entering S3, if not, entering S4; S3, entering sensitivity level calibration or frequency point calibration according to the pre-calibration instruction, and entering S4 after the calibration is completed; S4, executing the function corresponding to the project number, including frequency weighting processing, level linear processing, burst processing or repeated burst processing; S5, judging whether there is an instruction to change the project, if not, continue to execute the function corresponding to the project number, if so, execute the function corresponding to the changed project number. The present invention includes multiple frequency points, multiple sound pressure levels and various functions, and can provide burst and repeated burst sound signals on the basis of providing pure tone signals.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic metrology calibration, and in particular to a multifunctional calibration device and a control method for acoustic calibration. Background Art

[0002] As modern noise pollution becomes more and more serious, many cities have launched noise prevention and control. Sound level meters, as instruments for noise measurement, are also being used more and more. In addition, the sensitivity and frequency response of the microphone on the sound level meter need to be tested every day to prevent the sensitivity from drifting too much. The detection of the sensitivity of the microphone is mainly achieved through a sound calibrator, but the existing sound calibrators in China often have only a single frequency point or two frequency points, which is far from enough for detecting the frequency response of the microphone. In response to these problems, a multi-frequency sound calibrator is needed. It is a portable sound level meter calibration device, which is mainly used for periodic calibration of sound level meters and frequency response detection of test microphones. It is developed using digital signal processing technology and has a modular design. It has the advantages of multi-function, high performance, small size, low power consumption, and easy operation. At present, there are relatively few multi-frequency calibrators on the market, and there are not many calibrators with multi-frequency and multi-amplitude sound pressure calibration. When measuring multiple frequencies and multiple amplitudes, it is often necessary to carry several calibrators with different functions, which is inconvenient to carry and operate. Therefore, a portable calibrator that can measure multiple frequencies, multiple sound pressure levels, has a long working time and stable performance is the development trend.

[0003] The "High-temperature Calibration Device for Probe Microphone" disclosed in Chinese patent documents has a publication number of CN108007561B and a publication date of 2019-11-12. In view of the special needle-shaped structure of the probe microphone head and the characteristics of use in high-temperature environments, a new internal hollow three-way heat plug structure with a semi-partition and a coupling cavity structure for high-temperature calibration are designed to ensure that the sound field environment of the probe microphone and the standard microphone are consistent but the temperature fields are isolated from each other, and the probe microphone can be heated and calibrated separately. Compared with the calibration device commonly used for conventional microphones, this calibration device is specifically used for probe microphones, and can perform high-temperature calibration on the probe microphone, so that the calibration environment of the probe microphone is consistent with the actual use environment, thereby improving the accuracy and credibility of the calibration results of the probe microphone. However, the microphone calibration device of this technology calibrates the temperature sensitivity of the microphone through a hot air source and a duct. The coupling cavity structure and the control method of the device cannot cope with the problem that the sound calibrator needs to perform multi-frequency and multi-amplitude measurement and calibration. In addition, the device has a single function and only has pure tone signals, and cannot provide sound signals such as burst tone and repeated burst tone. Summary of the invention

[0004] The present invention aims to overcome the problem that the sound calibrator in the prior art has a single frequency point and a single function and only has a pure tone signal. A multifunctional calibration device and a control method for sound calibration are provided, which include multiple frequency points and diverse functions, can provide burst sound and repeated burst sound signals, and is provided with a closed-loop control process. Through circuits and digital signal processing technology, coarse and fine adjustments of the sound pressure level are respectively achieved, and the control accuracy is high.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A multifunctional calibration device for acoustic calibration, comprising:

[0007] An audio data acquisition and playback module is used to acquire data from the sound signal output module and output signals to the gain control module and the electrical signal output module;

[0008] A gain control module, used for adjusting the amplification factor of the signal and outputting a differential signal to the sound signal output module;

[0009] An acoustic signal output module, used for converting the differential signal into an acoustic signal and emitting sound in the coupling cavity;

[0010] The MCU control module is respectively connected to the audio data acquisition and playback module and the gain control module, and is used to control the operation of the calibration device.

[0011] The multifunctional calibration device in the present invention is mainly composed of an audio data acquisition and playback module, a gain control module, an electrical signal output module, an acoustic signal output module and an MCU control module. The MCU control module is connected to the audio data acquisition and playback module through bidirectional communication in an I2S manner, and the MCU control module controls the gain of the gain control module; the signal output by the gain control module sends out an acoustic signal through the acoustic signal output module, and the data collected in the acoustic signal output module is transmitted back to the audio data acquisition and playback module to form a closed-loop control; the signal output by the audio data acquisition and playback module is directly output from the electrical signal output module through a PHONEJACK port.

[0012] Preferably, the audio data acquisition and playback module includes an audio processor, the ADC unit of the audio processor acquires the sound-to-electrical signal transmitted by the standard microphone built into the coupling cavity and outputs the converted digital signal to the MCU control module; the DAC unit of the audio processor outputs the signal output from the MCU control module to the gain control module and the electrical signal output module through a low-pass filter.

[0013] The audio data acquisition and playback module in the present invention is divided into two parts: audio data acquisition and audio data playback. The standard microphone, operational amplifier circuit, ADC unit of the audio processor and MCU control module in the coupling cavity of the sound signal output module constitute a feedback system for audio data acquisition, and the MCU control module, the DAC module of the audio processor, the operational amplifier circuit, the electrical signal output module and the coupling cavity of the sound signal output module constitute a sound generation system for audio data playback.

[0014] Preferably, the gain control module includes a first-level gain circuit consisting of a first four-way selection switch and a first operational amplifier, and a second-level gain circuit consisting of a second four-way selection switch and a second operational amplifier; the gained signal is output to the sound signal output module through an audio power amplifier; and both four-way selection switches are connected to the MCU control module through an IO port.

[0015] The gain control module in the present invention is mainly used to adjust the amplification factor of the gain circuit, and is composed of two four-way selection switches, two operational amplifiers and one audio power amplifier. The two four-way selection switches can achieve 16 levels of amplification or attenuation. After the amplification or attenuation, the single-ended signal is converted into a differential signal through the audio power amplifier to drive the moving iron unit of the sound signal output module, thereby emitting a sound signal.

[0016] A control method for a multifunctional calibration device for acoustic calibration, comprising:

[0017] S1, system hardware initialization and read stored calibration information;

[0018] S2, determine whether there is a pre-calibration instruction input, if yes, go to S3, if no, go to S4;

[0019] S3, enter sensitivity level calibration or frequency point calibration according to the input pre-calibration instruction, and enter S4 after the calibration is completed;

[0020] S4. Execute the function specified by the project number, including frequency weighting processing, level linear processing, tone burst processing or repeated tone burst processing;

[0021] S5. Determine whether there is an instruction to change the item. If not, continue to execute the function corresponding to the item number. If yes, execute the function corresponding to the replaced item number.

[0022] The multifunctional calibration device of the present invention includes functions such as frequency weighting processing, level linear processing, tone burst processing and repeated tone burst processing, all of which include closed-loop control processes, and can control specific functions according to corresponding instructions input into the calibration device on a control panel or a touch screen; frequency weighting processing and level linear processing can generate pure tone signals for frequency response and level linearity testing of a sound level meter and linearity testing of a sound level meter; tone burst processing and repeated tone burst processing can be used to calibrate the time weighting of a sound level meter.

[0023] Preferably, the calibration information stored in S1 includes the sensitivity level of the standard microphone, the calibrated frequency, the calibrated sound pressure level, the calibrated digital signal amplitude, the correction value of each frequency point and the maximum sound pressure level of each frequency point. In the present invention, each frequency point is a central frequency point of a 1 / 3 octave in the range of 20 Hz to 16 kHz, and the data of the sensitivity level calibration and the frequency point calibration are stored in the Flash memory. In order to facilitate storage and reduce the number of Flash erasures, the storage area of ​​the Flash can be sector-planned, and each sector corresponds to a type of calibration information.

[0024] Preferably, the function in S4 includes a closed-loop control process, including:

[0025] S41, obtaining the frequency and amplitude of the set target signal and calculating the target sound pressure level;

[0026] The target signals in S42 and S41 are outputted through the acoustic signal output module and the electrical signal output module respectively;

[0027] S43, collecting actual signal data in the coupling cavity of the sound signal output module to obtain frequency and amplitude and calculate the actual sound pressure level;

[0028] S44, comparing the calculation results between the target signal and the actual signal, and adjusting the gain of the gain control module and the amplitude of the digital signal according to the comparison result;

[0029] S45, the adjusted signal is output to the moving iron unit in the coupling cavity through the gain control module to produce sound.

[0030] The closed-loop control in the present invention is a closed-loop control process of the amplitude of the sound signal. The target sound pressure level of the set target signal is used as a standard, the actual signal data fed back from the sound signal output module is calculated to obtain the actual sound pressure level, and the difference between the target sound pressure level and the actual sound pressure level is used as the basis for feedback control to adjust the gain of the gain control module and the amplitude of the digital signal. After a cyclic adjustment process, the adjustment coefficient calculated from the actual sound pressure level and the target sound pressure level is within a predetermined range and the difference between the two is less than the set value, and the control of the amplitude of the sound signal is completed and output for occurrence.

[0031] Preferably, when the actual sound pressure level is less than the target sound pressure level, the gain value of the gain control module is gradually increased so that the gain reaches a maximum value when the actual sound pressure level is less than the target sound pressure level; when the actual sound pressure level is greater than the target sound pressure level, the gain value of the gain control module is gradually reduced so that the gain reaches a minimum value when the actual sound pressure level is greater than the target sound pressure level.

[0032] In the present invention, a difference threshold is preset. When the absolute value of the difference between the actual sound pressure level and the target sound pressure level is greater than the difference threshold, the gain of the gain control module is gradually increased or decreased to achieve the purpose of adjusting the actual sound pressure level. When the absolute value of the difference between the two is less than the difference threshold, the adjustment coefficient of the digital signal obtained from the actual sound pressure level and the target sound pressure level is calculated, and the gain of the gain control module and the amplitude of the digital signal are adjusted according to the adjustment coefficient until the accuracy of the actual sound pressure level meets the requirements.

[0033] The present invention has the following beneficial effects: it contains multiple frequency points and has diverse functions, and can provide not only pure tone signals but also burst tone and repeated burst tone sound signals; a closed-loop control process is provided in the device, and through circuits and digital signal processing technology, coarse and fine adjustments of the sound pressure level are respectively achieved, and the control accuracy is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a structural block diagram of the calibration device of the present invention;

[0035] Figure 2 is a schematic diagram of an audio data acquisition and playback module in the calibration device of the present invention;

[0036] Figure 3 is a schematic diagram of a gain control module in the calibration device of the present invention;

[0037] Figure 4 is a schematic diagram of an MCU control module in the calibration device of the present invention;

[0038] Figure 5 is a flow chart of a control method of a calibration device of the present invention;

[0039] Figure 6 is a storage data planning diagram of a calibration device in an embodiment of the present invention;

[0040] Figure 7 is a flow chart of a closed-loop control process in an embodiment of the present invention;

[0041] Figure 8 It is a flow chart of the data playback process in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0043] like Figure 1 As shown, a multifunctional calibration device for acoustic calibration comprises:

[0044] The audio data acquisition and playback module 2 is used to collect data from the sound signal output module 5 and output signals to the gain control module 3 and the electrical signal output module 4; the gain control module 3 is used to adjust the signal amplification factor and output a differential signal to the sound signal output module 5; the sound signal output module 5 is used to convert the differential signal into an acoustic signal and emit a sound in the coupling cavity; the MCU control module 1 is respectively connected to the audio data acquisition and playback module 2 and the gain control module 3, and is used to control the operation of the calibration device.

[0045] The audio data acquisition and playback module includes an audio processor. The ADC unit of the audio processor collects the sound-to-electrical signal transmitted by the standard microphone built into the coupling cavity and outputs it to the MCU control module; the DAC unit of the audio processor outputs the signal output from the MCU control module through a low-pass filter to the gain control module and the electrical signal output module.

[0046] The gain control module includes a first-level gain circuit consisting of a first four-way selection switch and a first operational amplifier and a second-level gain circuit consisting of a second four-way selection switch and a second operational amplifier; the gained signal is output to the sound signal output module through the audio power amplifier; both four-way selection switches are connected to the MCU control module through the IO port.

[0047] The multifunctional calibration device in the present invention is mainly composed of an audio data acquisition and playback module, a gain control module, an electrical signal output module, an acoustic signal output module and an MCU control module. The MCU control module is connected to the audio data acquisition and playback module through bidirectional communication in an I2S manner, and the MCU control module controls the gain of the gain control module; the signal output by the gain control module sends out an acoustic signal through the acoustic signal output module, and the data collected in the acoustic signal output module is transmitted back to the audio data acquisition and playback module to form a closed-loop control; the signal output by the audio data acquisition and playback module is directly output from the electrical signal output module through a PHONEJACK port.

[0048] The audio data acquisition and playback module in the present invention is divided into two parts: audio data acquisition and audio data playback. The standard microphone, operational amplifier circuit, ADC unit of the audio processor and MCU control module in the coupling cavity of the sound signal output module constitute a feedback system for audio data acquisition, and the MCU control module, the DAC module of the audio processor, the operational amplifier circuit, the electrical signal output module and the coupling cavity of the sound signal output module constitute a sound generation system for audio data playback.

[0049] The gain control module in the present invention is mainly used to adjust the amplification factor of the gain circuit, and is composed of two four-way selection switches, two operational amplifiers and one audio power amplifier. The two four-way selection switches can achieve 16 levels of amplification or attenuation. After the amplification or attenuation, the single-ended signal is converted into a differential signal through the audio power amplifier to drive the moving iron unit of the sound signal output module, thereby emitting a sound signal.

[0050] like Figure 5 As shown, a control method of a multifunctional calibration device for acoustic calibration comprises:

[0051] S1. The system hardware is initialized and the stored calibration information is read; the calibration information stored in S1 includes the sensitivity level of the standard microphone, the calibrated frequency, the calibrated sound pressure level, the calibrated digital signal amplitude, the correction value of each frequency point and the maximum sound pressure level of each frequency point.

[0052] S2. Determine whether a pre-calibration instruction is input, if yes, go to S3, if no, go to S4.

[0053] S3. Enter sensitivity level calibration or frequency point calibration according to the input pre-calibration instruction, and enter S4 after the calibration is completed.

[0054] S4, execute the function corresponding to the project number, including frequency weighting processing, level linear processing, burst processing or repeated burst processing; the function in S4 includes a closed-loop control process, including:

[0055] S41, obtaining the frequency and amplitude of the set target signal and calculating the target sound pressure level;

[0056] The target signals in S42 and S41 are outputted through the acoustic signal output module and the electrical signal output module respectively;

[0057] S43, collecting actual signal data in the coupling cavity of the sound signal output module to obtain frequency and amplitude and calculate the actual sound pressure level;

[0058] S44, comparing the calculation results between the target signal and the actual signal, and adjusting the gain of the gain control module and the amplitude of the digital signal according to the comparison result;

[0059] S45, the adjusted signal is output to the moving iron unit in the coupling cavity through the gain control module to produce sound.

[0060] S5. Determine whether there is an instruction to change the item. If not, continue to execute the function corresponding to the item number. If yes, execute the function corresponding to the replaced item number.

[0061] When the actual sound pressure level is lower than the target sound pressure level, the gain value of the gain control module is gradually increased so that the gain reaches the maximum value when the actual sound pressure level is lower than the target sound pressure level; when the actual sound pressure level is higher than the target sound pressure level, the gain value of the gain control module is gradually reduced so that the gain reaches the minimum value when the actual sound pressure level is higher than the target sound pressure level.

[0062] The multifunctional calibration device of the present invention includes functions such as frequency weighting processing, level linear processing, tone burst processing and repeated tone burst processing, all of which include closed-loop control processes, and specific functions can be controlled according to corresponding instructions input into the calibration device on the control panel; frequency weighting processing and level linear processing can generate pure tone signals for frequency response and level linearity testing of the sound level meter and linearity testing of the sound level meter; tone burst processing and repeated tone burst processing can be used to calibrate the time weighting of the sound level meter.

[0063] In the present invention, each frequency point is a central frequency point of a 1 / 3 octave in the range of 20 Hz to 16 kHz. The data of sensitivity level calibration and frequency point calibration are stored in the Flash memory. In order to facilitate storage and reduce the number of Flash erase times, the Flash storage area can be sector-planned, and each sector corresponds to a type of calibration information.

[0064] The closed-loop control in the present invention is a closed-loop control process of the amplitude of the sound signal. The target sound pressure level of the set target signal is used as a standard, the actual signal data fed back from the sound signal output module is calculated to obtain the actual sound pressure level, and the difference between the target sound pressure level and the actual sound pressure level is used as the basis for feedback control to adjust the gain of the gain control module and the amplitude of the digital signal. After a cyclic adjustment process, the adjustment coefficient calculated from the actual sound pressure level and the target sound pressure level is within a predetermined range and the difference between the two is less than the set value, the control of the amplitude of the sound signal is completed and output for sounding.

[0065] In the present invention, a difference threshold is preset. When the absolute value of the difference between the actual sound pressure level and the target sound pressure level is greater than the difference threshold, the gain of the gain control module is gradually increased or decreased to achieve the purpose of adjusting the actual sound pressure level. When the absolute value of the difference between the two is less than the difference threshold, the adjustment coefficient of the digital signal obtained from the actual sound pressure level and the target sound pressure level is calculated, and the gain of the gain control module and the amplitude of the digital signal are adjusted according to the adjustment coefficient until the accuracy of the actual sound pressure level meets the requirements.

[0066] In the embodiment of the present invention, the calibration device is mainly composed of five parts, including an audio data acquisition and playback module, an electrical signal output module, an MCU control module, a gain control module, and an acoustic signal output module. Figure 2 The figure shows a schematic diagram of an audio data acquisition and playback module, which includes two parts, namely, audio data acquisition and audio data playback.

[0067] Audio data acquisition: refers to the use of the ADC unit of the domestic audio processor ES8388 to collect the sound-to-electricity signal transmitted by the standard microphone AWA14404 built into the coupling cavity, and output it to the MCU control module through the I2S interface. The MCU control module calculates the sound pressure level of the sound signal in the coupling cavity, which is an important part of the closed-loop control of the sound pressure level.

[0068] Audio data playback: refers to the process of using the DAC unit of the domestic audio processor ES8388 to convert the signal output from the MCU control module through the DAC and then output the signal through the low-pass filter. As can be seen from the figure, the output signals enter the gain control module and the electrical signal output module respectively. The electrical signal output module directly outputs the low-pass filter signal through the PHONEJACK port; the gain control module gains or attenuates the signal output by the DAC module, and outputs the sound signal through the sound signal output module. The size of the output signal of the audio processor DAC module can be controlled by the MCU control module.

[0069] like Figure 3 The figure shows a schematic diagram of a gain control module, which is mainly used to adjust the gain multiple of the gain circuit. The control unit is composed of two four-way selection switches, two operational amplifiers, and one audio power amplifier. The two four-way selection switches can realize 16 levels of amplification or attenuation. After the amplification or attenuation, the single-ended signal is converted into a differential signal through the audio power amplifier, and the moving iron unit of the sound signal output module is driven to emit a sound signal. The gain control module is used as a coarse adjustment, and together with the fine adjustment of the MCU control module, a closed-loop control of the sound pressure level is realized. The signal is input from the input end of the first four-way selection switch, the switch selection end of the first four-way selection switch is connected to the input end of the first operational amplifier, the output end of the first operational amplifier is connected to the input end of the second four-way selection switch, the switch selection end of the second four-way selection switch is connected to the input end of the second operational amplifier, and the output end of the second operational amplifier outputs the gain signal to the sound signal output module through the audio power amplifier; wherein the IO1 end, IO2 end of the first four-way selection switch and the IO3 end, IO4 end of the second four-way selection switch are all connected to the IO port of the MCU control module, which is used to select the path of the analog switch.

[0070] The acoustic signal output module is to output the differential signal output by the gain control module to the moving iron unit in the coupling cavity through the LEMO socket, realize the conversion of the electrical signal to the acoustic signal, and then make a sound in the coupling cavity. The electrical signal output module is to output the electrical signal of the low-pass filter through the PHONEJACK port, which can be used to calibrate the signal type, such as performing spectrum analysis on the signal.

[0071] like Figure 4The figure shows a schematic diagram of the MCU control module. The functions of the MCU control module include: obtaining the electrical signal of the standard microphone in the coupling cavity collected by the ADC unit of the audio processor, calculating the sound pressure level of the sound signal in the coupling cavity, and using the sound pressure level as a feedback signal. After determining the difference with the target sound pressure level, the MCU control module adjusts the gain of the gain control module; determines the type of signal that needs to be output at present, generates a specified AC signal, and outputs it through the DAC unit of the audio processor to realize the sound of the coupling cavity; controls the gain of the gain control module through the IO port of the MCU control module; controls the display of the OLED display, panel key input, project processing, etc., and can also control other necessary auxiliary components.

[0072] The audio processor realizes the generation and collection of audio signals. There are two types of audio signals. One is the feedback sound signal. The standard microphone installed in the coupling cavity is used to collect the sound signal in the coupling cavity as feedback, and the ADC unit of the audio processor is used for collection. The other is the generated sound signal, with a frequency of 20Hz to 16kHz, pure tone at the center frequency of 1 / 3 octave, and burst tone and repeated burst tone at a frequency of 4kHz. The pure tone signal can be set according to the needs of the user, and the generated signal is sent by the DAC unit of the audio processor. All audio signal data is generated by the MCU control module, and no additional signal generation circuit is required. The standard microphone of the coupling cavity, the operational amplifier circuit, the ADC unit of the audio processor, and the MCU control module constitute the feedback system. The MCU control module, the DAC unit of the audio processor, the operational amplifier circuit, the moving iron unit, and the coupling cavity constitute the sound generation system. The two systems constitute the sound generation and feedback adjustment of the sound calibration device to achieve precise control of the sound signal. The USB interface can be used for external power supply and communication with the PC host software to realize data management and other functions.

[0073] like Figure 5The figure shows a flow chart of the control method of the calibration device in the embodiment of the present invention. The system hardware is initialized and the stored calibration information is read; the previously saved sensitivity level calibration and frequency point calibration data are loaded from the storage system. If there is no stored information, the default value is used. The stored information includes the standard microphone sensitivity level, the frequency, sound pressure level, digital signal amplitude of the sensitivity level calibration, and the correction value of each frequency point of the frequency point calibration and the maximum sound pressure level of each frequency point. Each frequency point is a 1 / 3 octave center frequency point in the range of 20Hz to 16kHz. After the loading is completed, the global interrupt is turned on to start data collection and playback. Then it is determined whether there is a pre-calibration instruction currently input. When there is a pre-calibration instruction, the sensitivity level calibration or frequency point calibration function is entered according to the instruction content for calibration. After the calibration is completed, the function corresponding to the input project number is executed; when there is no pre-calibration instruction, the function corresponding to the project number is directly executed. Under one project number, multiple functions can be selected to run, including frequency weighting processing, level linear processing, burst processing or repeated burst processing, and these functions include closed-loop control process and data playback process. When the calibration device is working, it can be determined whether there is an instruction to change the item. If not, the function corresponding to the item number will continue to be executed. If there is an instruction to change the item, the function corresponding to the replaced item number will be executed. In this embodiment, the data of sensitivity level calibration and frequency point calibration are stored in the Flash memory. In order to facilitate storage and reduce the number of Flash erases, the storage area of ​​the Flash is Figure 6 In the layout shown, each sector corresponds to a type of calibration information.

[0074] In an embodiment of the present invention, the closed-loop control process of the acoustic signal amplitude is as follows: the MCU control module obtains the signal frequency and amplitude of the currently set target signal, and calculates the target sound pressure level; the MCU control module sends a signal of the specified frequency and amplitude to the audio processor through the I2S port; the DAC unit of the audio processor converts the data from digital to analog, and sends it to the gain control module in one way and to the electrical signal output module in the other way, and outputs it through the PHONEJACK interface; the signal is differentially output to the coupling cavity connected to the LEMO seat through the gain control module; the standard microphone in the coupling cavity transmits the data of the actual signal to the ADC unit of the audio data acquisition and playback module; the ADC unit of the audio processor converts the collected data from analog to digital and transmits it to the MCU control module through the I2S port; the MCU control module calculates the frequency, amplitude and actual sound pressure level of the actual signal, and compares the sound pressure level of the actual signal with that of the target signal; the MCU control module adjusts the gain of the gain control module and the amplitude of the digital signal according to the comparison result of the actual signal with the target signal; the adjusted signal is output to the moving iron unit of the coupling cavity through the gain control module to sound.

[0075] like Figure 7As shown, under the condition that the actual sound pressure level is less than the target sound pressure level by more than 2dB and the amplitude of the digital signal is greater than 0x006F0000, it is determined whether the gain of the gain control module has reached the maximum value. If the gain has not reached the maximum value, the gain of the gain control module is increased, and the actual sound pressure level is recalculated after stepping 2dB and compared with the target sound pressure level; if the gain has reached the maximum value, the next step of calculating the difference between the target sound pressure level and the actual sound pressure level is performed. Under the condition that the actual sound pressure level is not less than the target sound pressure level by more than 2dB and the amplitude of the digital signal is greater than 0x006F0000, it is determined whether the actual sound pressure level is greater than the target sound pressure level by more than 2dB and the amplitude of the digital signal is less than 0x00100000. If the condition is met, it is determined whether the gain of the gain control module has reached the minimum value. If the gain has not reached the minimum value, the gain of the gain control module is reduced, and the actual sound pressure level is recalculated after stepping 2dB and compared with the target sound pressure level; if the gain has reached the minimum value, the next step of calculating the difference between the target sound pressure level and the actual sound pressure level is performed. If neither the condition that the actual sound pressure level is more than 2 dB less than the target sound pressure level and the amplitude of the digital signal is greater than 0x006F0000 nor the condition that the actual sound pressure level is more than 2 dB greater than the target sound pressure level and the amplitude of the digital signal is less than 0x00100000 is met, the operation of directly calculating the difference between the target sound pressure level and the actual sound pressure level is performed.

[0076] After calculating the difference between the actual sound pressure level and the target sound pressure level, the adjustment coefficient of the digital signal is calculated. In this embodiment, the adjustment coefficient is Where SPL0 represents the actual sound pressure level in decibels, SPL s Indicates the target sound pressure level in decibels. After the adjustment coefficient is calculated, it is determined whether the sound pressure level lock flag in the calibration device is 1. If it is 1, it means it is locked, and if it is 0, it means it is not locked.

[0077] When the flag is 1, it is determined whether the adjustment coefficient of the digital signal satisfies 0.995<α<1.005. If the condition is met, the next step is to determine whether the difference between the actual sound pressure level and the target sound pressure level is less than 0.1dB. If the condition is not met, the amplitude of the digital signal is determined. When the amplitude of the digital signal is greater than 0x007FFFFF, it returns to determine whether the gain of the gain control module reaches the maximum value and performs the corresponding adjustment steps; when the amplitude of the digital signal is less than 0x00100000, it returns to determine whether the gain of the gain control module reaches the minimum value and performs the corresponding adjustment steps; when the amplitude of the digital signal is between 0x00100000 and 0x007FFFFF, the next step is to determine whether the difference between the actual sound pressure level and the target sound pressure level is less than 0.1dB. In this embodiment, the amplitude of the digital signal is represented by a hexadecimal number, and the first four digits "0x00" are not included in the calculation range of the amplitude value, and the last six digits represent the specific amplitude value of the digital signal.

[0078] In the step of judging whether the difference between the actual sound pressure level and the target sound pressure level is less than 0.1dB, if the difference is not less than 0.1dB, the sound pressure level adjustment lock mark position is set to 0, WAIT is displayed on the OLED display to wait for the sound pressure level adjustment and the process returns to the beginning to readjust; if the difference is less than 0.1dB, it means that the adjustment is completed, the sound pressure level adjustment lock mark position is set to 1, and OK is displayed on the OLED display to indicate that the adjustment is completed.

[0079] After the sound pressure level adjustment is completed, the sound signal data playback process begins. Figure 8 As shown, the data playback process is described by taking the frequency weighting processing process as an example. First, the frequency and amplitude of the signal set in the frequency weighting interface are read, and the amplitude of all sampling points of the signal is calculated. In this embodiment, 19200 sampling points are selected. All calculated amplitudes are stored in the cache, and all sampling point amplitude data are sent in batches. In this embodiment, 1200 data are sent to the DMA direct memory access and audio processor in each batch, and the amount of data that has been sent is recorded synchronously; after completing the sending of all sampling point data, the amount of data that has been sent is cleared, and the amplitude cache and data sending process are repeated; until the calibration device switches the interface or changes the signal frequency, it returns to the initial position of the entire playback process to obtain the new signal frequency and amplitude for the data playback process.

[0080] In the frequency weighting process of this embodiment, the instrument can generate a pure tone signal, which is mainly used for frequency response and level linearity testing of sound level meters. The formula for generating a pure tone signal is: Where P represents the amplitude. During the fine-tuning process of closed-loop control, the amplitude of the digital signal is P; f represents the frequency of the pure tone signal, and i represents the current discrete point of the signal; fs Indicates the audio sampling frequency. Under the frequency weighting function, the frequency of the signal can be adjusted cyclically from 20Hz to 16kHz at the center frequency point of 1 / 3 octave, and the signal amplitude can be adjusted cyclically from 94dB, 104dB and 114dB. In the level linear processing, like frequency weighting, it can also generate pure tone signals, which are mainly used for the linearity test of the sound level meter. The formula for generating pure tone signals is the same as that for frequency weighting processing; under the level linear function, the frequency of the signal can be adjusted cyclically from 20Hz to 16kHz at the center frequency point of 1 / 3 octave, and the signal amplitude can be adjusted cyclically from 90dB to 120dB, and the amplitude can be stepped by 1dB or 5dB.

[0081] The tone burst processing function of the device in this embodiment can be used to calibrate the time weighting of the sound level meter. The tone burst is a signal that generates one or several complete sinusoidal waveform pulse trains and emits sound through the coupling cavity. The tone burst frequency in this device is 4kHz, the signal period is 10s, the tone burst delay can be set to six types: 500ms, 200ms, 50ms, 10ms, 2ms and 0.25ms, and the amplitude can be adjusted cyclically from 90dB to 120dB, in steps of 1dB. The generation of the tone burst signal is similar to that of the pure tone signal. When the signal period is 10s, except for the sinusoidal waveform pulse, the amplitude of the remaining time signals is 0. The following is an explanation with a delay of 500ms: the sampling rate in this embodiment is 48kHz, so there are 12 sampling points in each cycle of the 4kHz sine wave. When the signal delay is 500ms, there are 2000 complete sine waves with a frequency of 4kHz. The amplitude of each sampling point is calculated using the formula generated by the pure tone signal. When the data is played, the complete sine wave is played 2000 times repeatedly, that is, after playing the 500ms signal, the remaining 9.5s time signal outputs 0 to generate a burst signal with a period of 10s and a signal delay of 500ms. The principle of the repeated burst processing function in this embodiment is similar to the burst processing function, except that the period of the repeated burst signal is 10 times the signal delay.

[0082] The above embodiments are further elaborations and illustrations of the present invention for ease of understanding, and are not limitations of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multifunctional calibration device for acoustic calibration, characterized in that: include: An audio data acquisition and playback module is used to acquire data from the sound signal output module and output signals to the gain control module and the electrical signal output module; It includes an audio processor, wherein the ADC unit of the audio processor collects the sound-to-electricity signal transmitted by the standard microphone built into the coupling cavity and outputs the converted digital signal to the MCU control module; A gain control module is used to adjust the amplification factor of the signal and output a differential signal to the sound signal output module; it includes a primary gain circuit composed of a first four-way selection switch and a first operational amplifier, and a secondary gain circuit composed of a second four-way selection switch and a second operational amplifier; the signal after gain is output to the sound signal output module through an audio power amplifier; both four-way selection switches are connected to the MCU control module through an IO port; An acoustic signal output module, used for converting the differential signal into an acoustic signal and emitting sound in the coupling cavity; The MCU control module is respectively connected to the audio data acquisition and playback module and the gain control module, and is used to control the operation of the calibration device; the actual signal data fed back from the sound signal output module is calculated to obtain the actual sound pressure level, and the difference between the target sound pressure level and the actual sound pressure level is used as the basis for feedback control to adjust the gain of the gain control module and the amplitude of the digital signal.

2. A multifunctional calibration device for acoustic calibration according to claim 1, characterized in that: The DAC unit of the audio processor outputs the signal output from the MCU control module to the gain control module and the electrical signal output module through a low-pass filter.

3. A control method for a multifunctional calibration device for acoustic calibration, applicable to the device as claimed in claim 1, characterized in that: include: S1, system hardware initialization and read stored calibration information; S2, determine whether there is a pre-calibration instruction input, if yes, go to S3, if no, go to S4; S3, enter sensitivity level calibration or frequency point calibration according to the input pre-calibration instruction, and enter S4 after the calibration is completed; S4. Execute the function specified by the project number, including frequency weighting processing, level linear processing, tone burst processing or repeated tone burst processing; Calculate the actual signal data fed back from the sound signal output module to obtain the actual sound pressure level, and use the difference between the target sound pressure level and the actual sound pressure level as the basis for feedback control to adjust the gain of the gain control module and the amplitude of the digital signal. After a cyclic adjustment process, when the adjustment coefficient calculated from the actual sound pressure level and the target sound pressure level is within a predetermined range and the difference between the two is less than a set value, the control of the sound signal amplitude is completed and the output is generated; S5. Determine whether there is an instruction to change the item. If not, continue to execute the function corresponding to the item number. If yes, execute the function corresponding to the replaced item number.

4. The control method of the multifunctional calibration device for acoustic calibration according to claim 3, characterized in that: The calibration information stored in S1 includes the sensitivity level of the standard microphone, the calibrated frequency, the calibrated sound pressure level, the calibrated digital signal amplitude, the correction value of each frequency point and the maximum sound pressure level of each frequency point.

5. The control method of a multifunctional calibration device for acoustic calibration according to claim 3 or 4, characterized in that: The functions in S4 include a closed-loop control process, including: S41, obtaining the frequency and amplitude of the set target signal and calculating the target sound pressure level; The target signals in S42 and S41 are outputted through the acoustic signal output module and the electrical signal output module respectively; S43, collecting actual signal data in the coupling cavity of the sound signal output module to obtain frequency and amplitude and calculate the actual sound pressure level; S44, comparing the calculation results between the target signal and the actual signal, and adjusting the gain of the gain control module and the amplitude of the digital signal according to the comparison result; S45, the adjusted signal is output to the moving iron unit in the coupling cavity through the gain control module to produce sound.

6. The control method of the multifunctional calibration device for acoustic calibration according to claim 5, characterized in that: When the actual sound pressure level is lower than the target sound pressure level, the gain value of the gain control module is gradually increased so that the gain reaches the maximum value when the actual sound pressure level is lower than the target sound pressure level; when the actual sound pressure level is higher than the target sound pressure level, the gain value of the gain control module is gradually reduced so that the gain reaches the minimum value when the actual sound pressure level is higher than the target sound pressure level.

7. The control method of the multifunctional calibration device for acoustic calibration according to claim 5, characterized in that: A difference threshold is preset. When the absolute value of the difference between the actual sound pressure level and the target sound pressure level is greater than the difference threshold, the gain of the gain control module is gradually increased or decreased to adjust the actual sound pressure level. When the absolute value of the difference between the actual sound pressure level and the target sound pressure level is less than the difference threshold, the adjustment coefficient of the digital signal obtained from the actual sound pressure level and the target sound pressure level is calculated, and the gain of the gain control module and the amplitude of the digital signal are adjusted according to the adjustment coefficient until the accuracy of the actual sound pressure level meets the requirements.

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