Low frequency calibration device and method for laser-piston sound generator method vector microphone

Abstract

The application discloses a kind of low-frequency calibration device and method of laser piston sound generator method vector microphone, it solves the technical problems that existing vector microphone calibration method exists in low frequency band calibration frequency range is limited, model dependency is strong, environmental noise interference is significant.It includes piston sound generator, laser interferometer, vector microphone and data acquisition system, piston sound generator includes piston and excitation source, piston cavity, end cover of piston cavity is opened with optical window, laser interferometer measures piston movement speed and displacement by optical window;Vector microphone is sealedly coupled to piston sound generator from the side wall of piston cavity through adapter;The electrical signal output of laser interferometer and vector microphone is connected to the input channel of data acquisition system.The calculation model of the piston sound generator in the application is clear, and is not dependent on the type of piston excitation source, and is strong in universality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microphone calibration, and particularly relates to a laser piston sound generator method vector microphone low-frequency calibration device and method. BACKGROUND

[0002] The vector microphone integrates a sound pressure sensor (microphone) and a particle velocity sensor, can simultaneously measure scalar sound pressure and vector particle velocity, and obtains sound intensity, sound power and other parameters through calculation to comprehensively describe the characteristics of the sound field, and is also called a P-U probe, an air sound vector sensor, etc. The vector microphone has the characteristics of small size and easy integration. The particle velocity sensor has a basic frequency-independent "8" directional pattern, can effectively suppress environmental background noise during measurement, and has obvious principle advantages in noise source positioning and identification applications compared with traditional scalar field measurement, and breaks through the minimum array aperture limit of the traditional sound detection system. The working frequency range of the vector microphone is generally 100Hz-10kHz, and the working frequency range can be as low as 10Hz or lower frequency in multi-target sound detection applications.

[0003] According to the actual needs of acoustic measurement, the common vector microphones are one-dimensional sensors and three-dimensional sensors. Among them, the one-dimensional vector microphone includes one particle velocity measurement channel and one sound pressure measurement channel, and the main application scenarios include directional voice pickup, sound impedance and sound absorption measurement, automobile NVH measurement, industrial equipment state monitoring and fault diagnosis, etc.; the three-dimensional vector microphone includes three mutually orthogonal particle velocity measurement channels and one sound pressure measurement channel, and can realize complete measurement of three-dimensional sound field, sound field visualization, noise source positioning and identification, etc.

[0004] The metrological parameters representing the performance of the vector microphone include: sound pressure and particle velocity sensitivity and frequency response, amplitude consistency, phase consistency, spatial directivity and noise floor, wherein the sound pressure and particle velocity sensitivity and frequency response of the vector microphone are basic. In 2006, Finn Jacobsen and Virginie Jaud of the Technical University of Denmark (DTU) proposed several possible vector microphone calibration methods, including: far-field comparison method of spherical sound source, near-field comparison method of single-pole sound source with rigid plane / spherical baffle opening, standing wave tube comparison method, and the calibration principles of each method are essentially the same, that is: in the sound field with clear theoretical relationship between sound pressure and particle velocity, the sound pressure measurement result of the calibrated microphone is taken as the reference, the reference value of the particle vibration velocity is calculated according to the theoretical model of the sound impedance, and the calibration of the sensor particle velocity sensitivity is realized.

[0005] The calibration frequency range of the spherical sound source far / near field comparison method can cover 10Hz-10kHz, however, the calibration accuracy of the particle velocity sensitivity depends on the theoretical relationship between the sound source radiation sound pressure and the particle velocity, that is, the modeling accuracy of the acoustic impedance, and the model of the acoustic impedance is highly dependent on the characteristic parameters of the special sound source and is not universal; in the standing wave tube and the free field device, the sound pressure and the particle velocity have a clear theoretical relationship, the calculation model of the acoustic impedance is not dependent on the sound source, but only related to the parameters such as the density and the sound speed of the transmission medium, and the calculation model of the acoustic impedance in the standing wave tube is also related to the wave number, the distance between the calibration position and the tube end, and is universal; however, the applicable calibration frequency range of the standing wave tube is related to the structural parameters thereof, and is generally 250Hz-4kHz; the applicable calibration frequency range of the free field device is related to the low frequency cutoff frequency and the working frequency range of the test sound source, and is generally 100Hz-20kHz. SUMMARY

[0006] The present application aims to provide a laser piston sound generator method vector microphone low frequency calibration device and method, to solve the technical problems of the existing vector microphone calibration method in the low frequency band, such as limited calibration frequency range, strong model dependence and significant environmental noise interference.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] In a first aspect, the present application provides a laser piston sound generator method vector microphone low frequency calibration device, comprising: a piston sound generator, a laser interferometer, a vector microphone and a data acquisition system, the piston sound generator comprising a piston and an excitation source, a piston cavity, an optical window is opened on the end cover of the piston cavity, the laser interferometer measures the piston movement speed and displacement through the optical window; the piston cavity end cover or side wall is also provided with a pressure sensor and a temperature sensor; the vector microphone is sealed and coupled to the piston sound generator through an adapter on the side wall of the piston cavity, the adapter has a rotation adjustment function, and the speed sensitive direction of the sound particle velocity sensor is adjusted to be consistent with the piston movement direction when the vector microphone particle velocity sensitivity is calibrated; the electrical signal output of the laser interferometer is connected to the input channel of the data acquisition system, and the electrical signal outputs of the sound pressure channel and the particle velocity channel of the vector microphone are connected to the data acquisition system respectively.

[0009] Further, the excitation source is one of an electromagnetic vibration table, a linear motor and a moving coil loudspeaker.

[0010] In a second aspect, the present application provides a laser piston sound generator method vector microphone low frequency calibration method, comprising the following steps:

[0011] Step 1: Vector microphone is coupled to the piston sound generator through the adapter of the piston cavity side wall, the sound pressure channel and the particle velocity channel of the vector microphone are connected to the input channel of the data acquisition system respectively;

[0012] Step 2: Start the piston sound generator, set the working frequency and driving voltage of the piston sound generator, the laser interferometer measures the piston movement speed and displacement through the optical window on the piston cavity end cover, and the electrical signal output is connected to the input channel of the data acquisition system;

[0013] Step 3: According to the lumped parameter model of the sound pressure in the piston sound generator, combined with the piston movement displacement measured by the laser interferometer, the static pressure and temperature measured by the pressure sensor and the temperature sensor, the sound pressure in the piston cavity is calculated, and the sensitivity of the sound pressure channel is calibrated according to the response voltage of the sound pressure channel of the vector microphone;

[0014] Step 4: Adjust the rotation adapter of the vector microphone and the piston cavity, and at the same time observe the response voltage of the particle velocity channel of the vector microphone through the data acquisition system, lock the rotation adapter when the response voltage appears maximum, at this time, the velocity sensitive direction of the particle velocity sensor of the vector microphone is consistent with the direction of the particle vibration velocity in the piston cavity;

[0015] Step 5: According to the axial distribution model of the particle vibration velocity in the piston sound generator, combined with the piston movement speed measured by the laser interferometer, the sensitivity of the particle velocity channel is calibrated according to the response voltage of the particle velocity channel of the vector microphone;

[0016] Step 6: Change the working frequency of the piston sound generator, repeat the above steps, and realize the calibration of the sound pressure, particle velocity sensitivity and frequency response of the vector microphone.

[0017] Further, the lumped parameter model of the sound pressure in the piston sound generator is:

[0018]

[0019] In the formula, p is the sound pressure amplitude in the piston cavity, γ is the specific heat ratio of air, p0 is the static pressure, R1 is the piston radius, x is the piston movement displacement, V0 is the volume of the closed cavity when the piston is in the equilibrium position, and Δp(H, L, W) is the error correction related to heat conduction, cavity leakage and sound pressure fluctuation.

[0020] Further, the sensitivity of the sound pressure channel is calibrated according to the response voltage of the sound pressure channel of the vector microphone, and the calculation formula is as follows:

[0021]

[0022] In the formula, V pVp is the response voltage of the sound pressure channel of the vector microphone, l p Vp is the response voltage of the sound pressure channel of the vector microphone, l

[0023] Further, the axial distribution model of the piston vibrator particle vibration speed is:

[0024]

[0025] In the formula, Δp(H, L) is a coupling correction coefficient of heat conduction and cavity leakage, v0 is the piston movement speed, R1 is the piston radius, a is the piston cavity radius, k is the wave number, z is the axial coordinate position with the piston center as the origin, v z is the particle vibration speed at position z in the piston cavity, and L is the piston cavity length.

[0026] Further, the vector microphone particle vibration speed channel sensitivity calibration is realized according to the response voltage of the vector microphone particle vibration speed channel, and the calculation formula is as follows:

[0027]

[0028] In the formula, V υ Vp is the response voltage of the sound pressure channel of the vector microphone, l υ Vp is the response voltage of the sound pressure channel of the vector microphone, l

[0029] Based on the above technical solutions, the embodiment of the present application can at least produce the following technical effects:

[0030] (1) The laser piston sound generator method vector microphone low-frequency calibration device provided by the present application, the lower limit of the frequency range of the piston sound generator method vector microphone calibration depends on the low-frequency piston sound generation technology, and the calibration frequency can cover at least 10Hz-100Hz. The piston sound generator is integrated as a standard equipment module in the device, and the lower limit of the calibration frequency can reach 0.01Hz or even lower.

[0031] (2) The laser piston sound generator method vector microphone low-frequency calibration method provided by the present application, the sound coupling mode of the vector microphone and the piston cavity is clear, the calculation model of the sound pressure and the axial particle vibration speed in the piston cavity is given, the piston movement displacement and speed are measured by the laser interferometer, the sound pressure and the particle vibration speed at the calibration position are calculated, and the absolute method calibration of the sound pressure and the particle vibration speed sensitivity of the vector microphone is realized. The calculation model of the sound pressure and the particle vibration speed in the piston sound generator is clear, and is not dependent on the type of the piston excitation source, and has strong universality. BRIEF DESCRIPTION OF DRAWINGS

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention;

[0034] In the figure: 1. Piston generator; 11. Piston and excitation source; 12. Piston cavity; 2. Laser interferometer; 3. Vector microphone; 31. Sound pressure channel; 32. Particle velocity channel; 4. Data acquisition system; 5. Pressure sensor; 6. Temperature sensor. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0036] Example 1

[0037] like Figure 1 As shown, this invention provides a low-frequency calibration device for a vector microphone using a laser piston generator, comprising a piston generator 1, a laser interferometer 2, a vector microphone 3, and a data acquisition system 4, with the following specific configuration: The piston generator 1 consists of a piston, an excitation source 11, and a piston cavity 12. An optical window is opened on the end cap of the piston cavity 12. The laser interferometer 2 measures the piston's movement speed and displacement through the optical window. In addition, a pressure sensor 5 and a temperature sensor 6 are also provided on the end cap or side wall of the piston cavity 12. The vector microphone 3 is sealed and coupled to the piston generator from the side wall of the piston cavity 12 through an adapter. The adapter has a rotation adjustment function, which adjusts the velocity sensing direction of the sound particle velocity sensor to be consistent with the piston's movement direction during the calibration of the vector microphone 3's particle velocity sensitivity. The electrical signal output of the laser interferometer 2 is connected to the input channel of the data acquisition system 4, and the electrical signal outputs of the sound pressure channel 31 and the particle velocity channel 32 of the vector microphone 3 are respectively connected to the data acquisition system 4.

[0038] In the embodiment, the piston excitation source can be selected from an electromagnetic vibration table, a linear motor, a moving coil loudspeaker, etc., the arrangement of the optical measurement window on the piston cavity and the laser interferometer is related to the piston excitation source, and any measurement mode and layout capable of realizing piston movement displacement and speed measurement can be replaced.

[0039] Embodiment 2

[0040] The application provides a low-frequency calibration method for a laser piston sound generator method vector microphone, comprising the following steps:

[0041] Step 1: the vector microphone is sealed and coupled to the piston sound generator through an adapter on the side wall of the piston cavity, and the sound pressure channel and the particle vibration velocity channel of the vector microphone are connected to the input channels of a data acquisition system, respectively.

[0042] Step 2: the piston sound generator is started, the working frequency and the driving voltage of the piston sound generator are set, the laser interferometer measures the piston movement speed and displacement through the optical window on the end cover of the piston cavity, and the electrical signal output is connected to the input channel of the data acquisition system.

[0043] Step 3: according to the lumped parameter model of the radiation sound pressure in the piston sound generator, such as formula (1), in combination with the piston movement displacement measured by the laser interferometer, the static pressure and the temperature measured by the pressure sensor and the temperature sensor, the sound pressure in the piston cavity is calculated, and according to the response voltage of the sound pressure channel of the vector microphone, the sensitivity calibration of the sound pressure channel can be realized, as shown in formula (2).

[0044]

[0045] In the formula, p is the sound pressure amplitude in the piston cavity, γ is the specific heat ratio of air, p0 is the static pressure, R1 is the piston radius, x is the piston movement displacement, V0 is the volume of the closed cavity when the piston is in the equilibrium position, and Δp(H, L, W) is an error correction related to heat conduction, cavity leakage and sound pressure fluctuation.

[0046]

[0047] In the formula, V p is the response voltage of the sound pressure channel of the vector microphone, l p is the sensitivity of the sound pressure channel of the vector microphone.

[0048] Step 4: the rotating adapter coupled with the piston cavity of the vector microphone is adjusted, and the response voltage of the particle vibration velocity channel of the vector microphone is observed through the data acquisition system at the same time, the rotating adapter is locked when the response voltage reaches the maximum value, and at this moment, the speed sensitive direction of the particle vibration velocity sensor of the vector microphone is consistent with the direction of the particle vibration speed in the piston cavity.

[0049] Step 5: According to the axial distribution model of the piston sound generator particle vibration velocity, such as formula (3), combined with the laser interferometer measured piston movement velocity, the particle vibration velocity channel sensitivity can be calibrated according to the response voltage of the vector microphone particle vibration velocity channel, as shown in formula (4). Wherein, the sound pressure error correction involved in formula (3) is composed of sound pressure fluctuation correction and thermal conduction, cavity leakage coupling correction, and the influence of sound pressure fluctuation effect can be ignored through the optimization of the piston cavity structure parameters, here, only the thermal conduction and cavity leakage coupling correction Δp(H, L) are considered.

[0050]

[0051] In the formula, Δp(H, L) is the coupling correction coefficient of thermal conduction and cavity leakage, υ0 is the piston movement velocity, R1 is the piston radius, a is the piston cavity radius, k is the wave number, z is the axial coordinate position with the piston center as the origin, υ(z) is the particle vibration velocity at position z in the piston cavity, and L is the piston cavity length. z

[0052]

[0053] In the formula, V is the response voltage of the vector microphone particle vibration velocity channel, l is the vector microphone particle vibration velocity channel sensitivity. υ υ

[0054] Step 6: Change the working frequency of the piston sound generator, repeat the above steps to realize the calibration of the vector microphone sound pressure, particle vibration velocity sensitivity and frequency response.

[0055] The basic principles and main features of the present application and the advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.​​​

Claims

1. A low-frequency calibration device for a laser piston transmitter normal vector microphone, characterized in that, It comprises a piston sound generator, a laser interferometer, a vector microphone and a data acquisition system, the piston sound generator comprises a piston and an excitation source, a piston cavity, an optical window is opened on the end cover of the piston cavity, the laser interferometer measures the piston movement speed and displacement through the optical window; the piston cavity end cover or side wall is also provided with a pressure sensor and a temperature sensor; the vector microphone is sealedly coupled to the piston sound generator through an adapter from the side wall of the piston cavity, the adapter has a rotation adjustment function, when the vector microphone particle vibration speed sensitivity is calibrated, the speed sensitive direction of the sound particle vibration speed sensor is adjusted to be consistent with the piston movement direction; the electrical signal output of the laser interferometer is connected to the input channel of the data acquisition system, and the electrical signal outputs of the sound pressure channel and the particle vibration speed channel of the vector microphone are connected to the data acquisition system respectively. The excitation source is one of an electromagnetic vibration table, a linear motor and a moving coil loudspeaker.

2. The low frequency calibration apparatus for a laser-piston acoustic radiator phasor microphone of claim 1, wherein, It comprises the following steps:

3. A low frequency calibration method of a laser-piston sound generator method vector microphone, the calibration is performed by using the low frequency calibration device of the laser-piston sound generator method vector microphone according to claim 1 or 2, characterized in that, Step 1: sealingly coupling the vector microphone to the piston sound generator through the adapter of the piston cavity side wall, and connecting the sound pressure channel and the particle vibration speed channel of the vector microphone to the input channel of the data acquisition system respectively; Step 2: starting the piston sound generator, setting the working frequency and driving voltage of the piston sound generator, and measuring the piston movement speed and displacement through the optical window on the end cover of the piston cavity, and connecting the electrical signal output to the input channel of the data acquisition system; Step 3: according to the lumped parameter model of the radiated sound pressure in the piston sound generator, combining the piston movement displacement measured by the laser interferometer, the static pressure and temperature measured by the pressure sensor and the temperature sensor, the sound pressure in the piston cavity is calculated, and the sensitivity calibration of the sound pressure channel is realized according to the response voltage of the sound pressure channel of the vector microphone; Step 4: adjusting the rotation adapter of the vector microphone and the piston cavity, and observing the response voltage of the particle vibration speed channel of the vector microphone through the data acquisition system at the same time, and locking the rotation adapter when the response voltage appears the maximum value, at this time, the speed sensitive direction of the particle vibration speed sensor of the vector microphone is consistent with the direction of the particle vibration speed in the piston cavity; Step 5: according to the axial distribution model of the particle vibration speed in the piston sound generator, combining the piston movement speed measured by the laser interferometer, and realizing the sensitivity calibration of the particle vibration speed channel according to the response voltage of the particle vibration speed channel of the vector microphone; Step 6: changing the working frequency of the piston sound generator, repeating the above steps, and realizing the sensitivity and frequency response calibration of the sound pressure and particle vibration speed of the vector microphone. The lumped parameter model of the radiated sound pressure in the piston sound generator is as follows:

4. The laser-piston phonic vector microphone low frequency calibration method of claim 3, wherein, In the formula, p is the sound pressure amplitude in the piston cavity, γ is the specific heat ratio of air, p0 is the static pressure, R1 is the piston radius, x is the piston movement displacement, V0 is the volume of the closed cavity when the piston is at the equilibrium position, and Δp(H, L, W) is the error correction related to heat conduction, cavity leakage and sound pressure fluctuation. The sensitivity calibration of the sound pressure channel is realized according to the response voltage of the sound pressure channel of the vector microphone, and the calculation formula is as follows:

5. The laser-piston phonic vector microphone low frequency calibration method of claim 4, wherein, The axial distribution model of the particle vibration speed in the piston sound generator is as follows: where V p is the response voltage of the pressure channel of the vector microphone, l p is the sensitivity of the pressure channel of the vector microphone.

6. The laser-piston phonic vector calibrator method of claim 3, wherein, ​ where Δp(H,L) is the coupling correction factor for heat conduction and cavity leakage, v0is the piston motion velocity, R1is the piston radius, a is the piston cavity radius, k is the wave number, z is the axial coordinate position with the piston center as the origin, v z is the particle vibration velocity at position z in the piston cavity, and L is the piston cavity length.

7. The laser-piston phonic vector microphone low frequency calibration method of claim 6, wherein, The particle velocity channel sensitivity is calibrated according to the response voltage of the particle velocity channel of the vector microphone, and the calculation formula is as follows: In the formula, V υ is the response voltage of the particle velocity channel of the vector microphone, l υ is the sensitivity of the particle velocity channel of the vector microphone.

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