CN-121977689-A - Microphone dynamic characteristic calibration system and method based on substitution method principle

CN121977689ACN 121977689 ACN121977689 ACN 121977689ACN-121977689-A

Abstract

The invention provides a microphone dynamic characteristic calibration system and method based on an alternative method principle, and relates to the technical field of detection and sensing. Based on the principle of substitution, a digital closed-loop control acoustic horn traveling wave tube calibration device is established, and acoustic attenuation under the full frequency band of acoustic waveguides with different lengths is obtained by a system full frequency band dynamic calibration method, so that the measurement result of a monitoring system can be corrected. In the field of aeroengine acoustic microphones, the measurement result of a noise measurement monitoring system can be corrected within an allowable error range, namely, the correction quantity and an experimentally measured value are added to obtain a final correction value, the test precision is improved, more accurate data are provided for the relation between subsequent exploration sound pressure and other physical quantities, and the method is suitable for the situation that a standard microphone cannot be obtained due to condition limitation.

Inventors

LUAN XIAOCHI
ZHAO FENGTONG
SHA YUNDONG
GUO XIAOPENG

Assignees

沈阳航空航天大学

Dates

Publication Date: 20260505
Application Date: 20251224

Claims (4)

1. A microphone dynamic characteristic calibration system based on an alternative method principle is characterized by comprising a hardware part and a software part; the hardware part comprises a traveling wave tube calibration device, a data acquisition instrument, a signal generator, a power amplifier, a power supply and a computer; The power supply provides power for all parts of the system; The traveling wave tube calibration device comprises a sound source, a straight pipeline, a reference microphone, a standard microphone or a calibrated microphone and a silencer, wherein the sound source is arranged at one end of the straight pipeline, the sound source is connected with a power amplifier and a signal generator, sound waves with specified frequency are generated under the control of the signal generator, the sound waves propagate along the straight pipeline, the silencer without a reflecting end is arranged at the other end of the straight pipeline, the sound source adopts a digital closed-loop control sound horn, the standard microphone is arranged when instructions of a feedback control module of a software part are executed, the calibrated microphone is arranged when instructions of the calibration control module are executed, the reference microphone and the standard microphone (the calibrated microphone) are oppositely arranged on a pipe wall of one end, close to the silencer, of the straight pipeline, the standard microphone is calibrated by a professional mechanism, the sensitivity of the standard microphone is constant within a frequency response range, and a test result is accurate and reliable; The power amplifier, the signal generator and the data acquisition instrument are sequentially connected, and the data acquisition instrument is connected with the computer; the data acquisition instrument is connected with the reference microphone, the standard microphone (or the calibrated microphone), the signal generator and the display, and acquires the sound pressure signal of the reference microphone, the sound pressure signal of the standard microphone (or the sound pressure signal of the calibrated microphone) and the voltage signal output by the signal generator in the full frequency band respectively; The signal generator is connected with the data acquisition instrument and the power amplifier, software in the data acquisition instrument controls the signal generator to output electric signals with different frequencies and different voltage amplitudes, and the electric signals output by the signal generator are amplified by the power amplifier; The power amplifier is connected with the signal generator and the sound source and is used for amplifying the electric signal output by the signal generator and inputting the electric signal to the sound source so that the sound source sounds according to the designated frequency and the sound pressure level; the computer comprises a display, a memory and a processor, wherein the display is used for displaying data acquired by the data acquisition instrument, the memory is used for storing program instructions of the software part, and the processor is used for executing the program instructions of the software part; The software part comprises a feedback control module and a calibration control module; The function of the feedback control module is to ensure that the sound pressure levels at the calibrated microphone mounting locations are all equal within a given calibration frequency range; in the system operation, the feedback control module controls the signal generator to send sine signals with specified frequency and amplitude and excites the sound source to generate sound waves, and the feedback control module continuously adjusts the sound source to generate sound waves according to the obtained measurement result of the standard microphone through the signal generator, finally ensures that the sound pressure at the installation position of the calibrated microphone reaches and is kept at a target value; The calibration control module is used for obtaining a full-frequency amplitude-frequency characteristic correction curve of the calibrated microphone, reading a voltage amplitude file of the signal generator generated by the feedback control module, starting calibration, carrying out sensitivity operation of the calibrated microphone according to a related mathematical relation, controlling the signal generator to send out signals with designated frequency and amplitude, automatically adjusting sampling frequency and sampling time to ensure full-period sampling, and adopting a proper window function to avoid fence effect and energy leakage in the digital signal processing process.
2. The microphone dynamic characteristic calibration system based on the principle of substitution method as set forth in claim 1, wherein the calibration process of the calibration control module is as follows: setting calibration parameters including calibration frequency bands, sweep intervals, target sound pressure levels, feedback microphone sensitivity and feedback control times; Recording axial position of reference microphone Circumferential position Axial position of standard microphone Circumferential position The radius of the sound tube is a; let the coordinates of the reference microphone and the standard microphone be respectively And Based on the circular duct sound pressure expression, the sound pressures at two points, namely the reference microphone and the standard microphone, are respectively expressed as: ; ; wherein m and n are mode numbers, m is a circumferential mode number, and n is a radial mode number; as a first class of m-order Bessel functions, Is that Is used for the root of (a), 、、、 Are expressed as constants of the equation, Representing the axial wavenumber in the (m, n) mode condition; When the sound in the tube is plane wave, the mode numbers m and n are 0, and when the sound source is only on the upstream boundary side of the tube, the backward sound wave in the tube can be written as forward sound wave The number of times of the number of times, The sound pressures of the two points of the reference microphone and the standard microphone are: ; ; wherein, C is the amplitude of the incident plane wave, and k z represents the circumferential wave number; The transfer function of the two points is: ; from this transfer function, it is understood that the transfer function between the sound pressures of two points at each frequency is lower than the plane wave cut-off frequency, as long as the duct size, the microphone mounting position, and the end boundary are determined Is constant, and thus calibrated by this property of the sound field in the pipe, i.e. by the sound pressure at this point of the reference microphone And transfer function between two points of reference microphone and standard microphone Obtaining sound pressure at the point of calibrated microphone ; After obtaining the two measurements, the sensitivity of the calibrated microphone is calculated according to the following transfer function formula: ; ; ; ; Wherein S R (f) is the sensitivity of the reference microphone, S S (f) is the sensitivity of the standard microphone, S C (f) is the sensitivity of the calibrated microphone, H A (f) is the transfer function from the sound source to the reference microphone position in the calibrating device, H B (f) is the transfer function from the sound source to the standard microphone position (or the calibrated microphone) in the calibrating device, H S (f) is the transfer function between the standard microphone and the reference microphone, and H C (f) is the transfer function between the calibrated microphone and the reference microphone.
3. A microphone dynamic characteristic calibration method based on the substitution principle is characterized in that the microphone dynamic characteristic calibration system based on the substitution principle is realized based on the substitution principle according to claim 1, firstly, a measurement result of a standard microphone is obtained under a given condition, then, a calibrated microphone is used for testing under the same condition, and further, the ratio of the sensitivity of the calibrated microphone to the sensitivity of the standard microphone is obtained, and the method specifically comprises the following steps: Step 1, constructing a microphone dynamic characteristic calibration system based on an alternative method, oppositely installing a standard microphone and a reference microphone, and operating a feedback control module to obtain a voltage amplitude file output by a signal generator under different frequencies for calling and reading by a calibration control module in the next step; step 2, replacing the standard microphone with a calibrated microphone, wherein the installation position is unchanged, and the connection sequence is unchanged; Step 3, operating a calibration control module in the dynamic calibration system, and carrying out sensitivity operation of the microphone according to a related mathematical relation; And 4, using the sensitivity of the obtained microphone to calibrate the target microphone.
4. The method for calibrating dynamic characteristics of a microphone based on the principle of substitution method according to claim 3, wherein the specific method of step 3 is as follows: setting a calibration frequency range to be 30 Hz-13 kHz, setting a sweep frequency interval to be 5Hz, setting a target sound pressure to be 110dB, and sequentially starting corresponding equipment under the condition of ensuring wiring to be error-free; setting calibration parameters including calibration frequency bands, sweep frequency intervals, target sound pressure levels, feedback microphone sensitivity and feedback control times; Step 3.3, recording position coordinates of the reference microphone and the standard microphone, and performing sensitivity operation according to the related mathematical relationship; Recording axial position of reference microphone And circumferential position Axial position of standard microphone And circumferential position The radius of the sound tube is a; let the coordinates of the reference microphone and the standard microphone be respectively And Based on the circular duct sound pressure expression, sound pressures of the reference microphone and the standard microphone are expressed as: ; ; wherein m and n are mode numbers, m is a circumferential mode number, and n is a radial mode number; as a first class of m-order Bessel functions, Is that Is used for the root of (a), 、、、 Are expressed as constants of the equation, Representing the axial wavenumber in the (m, n) mode condition; When the sound in the pipe is plane wave, the mode numbers m and n are both 0, if the sound source exists on the upstream boundary side of the pipe, the reverse sound wave in the pipe is written as R p times of the forward sound wave, R p is the plane wave complex reflection coefficient of the tail end, and at the moment, the sound pressures of the reference microphone and the standard microphone are written as follows: ; ; wherein, C is the amplitude of the incident plane wave, and k z represents the circumferential wave number; The transfer function of the reference microphone and the standard microphone is: ; from this transfer function, it is understood that the transfer function between the sound pressures of two points at each frequency is lower than the plane wave cut-off frequency, as long as the duct size, the microphone mounting position, and the end boundary are determined Is constant, and thus calibrated by this property of the sound field in the pipe, i.e. by the sound pressure of the reference microphone And transfer function between reference microphone and standard microphone Obtaining sound pressure of calibrated microphone ; After obtaining the two measurements, the sensitivity of the calibrated microphone is calculated according to the following transfer function formula: ; ; ; ; Wherein S R (f) is the sensitivity of the reference microphone, S S (f) is the sensitivity of the standard microphone, S C (f) is the sensitivity of the calibrated microphone, H A (f) is the transfer function from the sound source to the reference microphone position in the calibrating device, H B (f) is the transfer function from the sound source to the standard microphone position (or the calibrated microphone) in the calibrating device, H S (f) is the transfer function between the standard microphone and the reference microphone, and H C (f) is the transfer function between the calibrated microphone and the reference microphone.

Description

Microphone dynamic characteristic calibration system and method based on substitution method principle Technical Field The invention relates to the technical field of detection and sensing, in particular to a microphone dynamic characteristic calibration system and method based on an alternative method principle. Background With the continuous development of civil aviation industry, the influence of noise caused by the activities of aircrafts on human beings is more and more prominent. The aircraft noise has the characteristics of high sound pressure level and wide influence range, on one hand, the aircraft noise can cause different degrees of damage to the hearing and health of people, interfere the normal life of residents in communities around an airport, and on the other hand, the aircraft noise can damage aircraft parts when serious, so that the stability and the integrity of an aircraft structure are threatened. In order to accurately test various parameters of noise, the aeroengine noise testing technology needs to be developed. The primary device for detecting noise is a noise microphone, of which the lead-out noise microphone is of a relatively classical type, and is generally composed of an acoustic probe, acoustic waveguide, microphone unit, preamplifier and other special structures and housings. Microphone operation begins with a microphone, which is responsible for converting sound waves (sound pressure changes) into weak electrical signals. High quality test condenser microphones are commonly used because of their stable performance, wide dynamic range and flat frequency response. In order to ensure accurate measurement, weak electric signals acquired by the microphone are amplified and impedance transformed by the preamplifier. The signal then enters a signal processing and analysis unit. The signals are weighted by the frequency weighting network to obtain decibel values with more evaluation significance. Meanwhile, the time weighting and effective value detector can perform time average processing on the signals, and finally key parameters such as instantaneous sound level, maximum sound level, equivalent continuous sound level and the like are obtained. Modern digital instruments typically employ digital detection techniques and analog-to-digital (a/D) conversion to convert analog signals to digital signals for subsequent processing. The portable handheld electronic device is high in reliability, can work for a long time, is low in cost, has good capability of preventing various bad weather, and can be held by a hand, so that the portable electronic device is widely applied. However, in practical use, the acoustic signal measured by the noise measurement and monitoring system is attenuated due to factors such as viscous damping of air in the acoustic waveguide, especially in the high frequency band. Conventional measurement microphone calibration has two ways, field calibration and laboratory calibration. In-situ calibration typically uses a sound level calibrator, which compares the output voltage of the measurement microphone with a standard sound pressure emitted by the sound level calibrator to obtain the sensitivity of the microphone being calibrated. The field calibration can only provide standard sound pressure at a single frequency. Laboratory calibration methods include substitution, reciprocity, comparison, electrostatic excitation, etc., which also have higher calibration accuracy, but all require specific calibration equipment. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a microphone dynamic characteristic calibration system and method based on an alternative method principle, a digital closed-loop control acoustic horn traveling wave tube calibration device is established based on the alternative method principle, and acoustic attenuation amounts under the full frequency bands of acoustic waveguides with different lengths are obtained through a system full frequency band dynamic calibration method, so that the measurement result of a monitoring system can be corrected. In order to solve the technical problems, the invention adopts the following technical scheme: In one aspect, the invention provides a microphone dynamic characteristic calibration system based on the principle of substitution method, which comprises a hardware part and a software part; the hardware part comprises a traveling wave tube calibration device, a data acquisition instrument, a signal generator, a power amplifier, a power supply and a computer; The power supply provides power for all parts of the system; The traveling wave tube calibration device comprises a sound source, a straight pipeline, a reference microphone, a standard microphone or a calibrated microphone and a silencer, wherein the sound source is arranged at one end of the straight pipeline, the sound source is connected with a power amplifier and a signal generator, sound waves with specified frequ