Method for measuring acoustic parameters of material

Abstract

The invention relates to the technical field of acoustic measurement, and particularly provides a method for measuring acoustic parameters of a material, which comprises the following steps of: acquiring geometric parameters and an actual sound absorption coefficient of an impedance tube and a sound pressure signal propagating in the impedance tube; a blank pipe simulation model of the impedance pipe is constructed based on the geometric parameters, the inner pipe wall flow resistance rate and the corresponding simulation sound absorption coefficient of the impedance pipe are obtained, and under the condition that the difference value of the simulation sound absorption coefficient and the actual sound absorption coefficient is smaller than or equal to a preset threshold value, the corresponding inner pipe wall flow resistance rate serves as the simulation flow resistance rate; performing simulation based on the simulation flow resistivity to obtain the acoustic impedance of the inner surface of the impedance tube so as to calculate the wavenumber loss factor of the impedance tube; calculating the actual wave number of the impedance tube based on an iterative algorithm and the wave number loss factor; based on the geometric parameters, the sound pressure signals and the actual wave number, acoustic parameters of the to-be-tested material are calculated. The problem that in the prior art, loss in an impedance tube cannot be accurately corrected, and consequently the accuracy is low when acoustic parameters of a material are measured is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic measurement, and particularly to a method for measuring acoustic parameters of materials. Background Art

[0002] An impedance tube is a key instrument in acoustic measurement, and its importance increases with the development of audio technology and acoustic engineering. By controlling the acoustic environment, the impedance tube can accurately measure the acoustic parameters of materials. At the same time, calibrating the impedance tube is beneficial to improving its measurement accuracy.

[0003] Existing methods for calibrating the impedance tube: one is microphone phase error correction; the other is wavenumber transmission loss correction. Microphone phase error correction can be divided into reciprocal calibration and synchronous calibration, both of which correct the error caused by the microphone by normalizing the signal received by the microphone, but cannot correct the loss inside the impedance tube; the wavenumber transmission loss correction believes that the standard wavenumber theory attenuation formula underestimates the actual attenuation loss inside the impedance tube. By assuming that the reflection coefficient R = 1 at the rigid wall end, the theoretical attenuation value of the wavenumber is iterated to approach the true value. However, in the case where the impedance tube wall is non-rigid and the wavenumber loss is large, iteratively correcting with the theoretical attenuation value of the wavenumber often cannot obtain the correct loss inside the impedance tube.

[0004] Aiming at the problem that the loss inside the impedance tube in the related technology cannot be accurately corrected, resulting in low accuracy when measuring the acoustic parameters of materials, no effective solution has been proposed yet. Summary of the Invention

[0005] A method for measuring acoustic parameters of materials provided by an embodiment of the present invention can at least solve the problem that the loss inside the impedance tube in the related technology cannot be accurately corrected, resulting in low accuracy when measuring the acoustic parameters of materials.

[0006] A method for measuring acoustic parameters of materials provided by an embodiment of the present invention includes: obtaining the geometric parameters of the impedance tube, the actual absorption coefficient, and the sound pressure signal propagating inside the impedance tube, where the impedance tube is used to measure the acoustic parameters of the material to be measured; constructing an empty tube simulation model of the impedance tube based on the geometric parameters to obtain the flow resistivity of the inner tube wall of the impedance tube and the corresponding simulated absorption coefficient. When the difference between the simulated absorption coefficient and the actual absorption coefficient is less than or equal to a preset threshold, the corresponding flow resistivity of the inner tube wall is used as the simulated flow resistivity; simulating the acoustic impedance of the inner surface of the impedance tube based on the simulated flow resistivity to calculate the wavenumber loss factor of the impedance tube; calculating the actual wavenumber of the impedance tube based on the iterative algorithm and the wavenumber loss factor; calculating the acoustic parameters of the material to be measured based on the geometric parameters, the sound pressure signal, and the actual wavenumber.

[0007] The measurement method of material acoustic parameters provided by the embodiments of the present invention, after obtaining the acoustic impedance of the inner surface of the impedance tube through simulation based on the simulated flow resistivity, the method further includes: establishing a spatial rectangular coordinate system XYZ with the cross-section center of one end of the impedance tube as the coordinate origin, and determining the wave equation of the sound pressure signal, wherein the Z-axis direction is the propagation direction of the sound pressure signal along the impedance tube; performing variable separation processing on the wave equation to obtain the propagation equation of the sound pressure signal in the corresponding axis direction including the time variable; simplifying the propagation equation to obtain the pressure equations of the sound pressure signal in the X-axis direction and the Y-axis direction without the time variable; substituting the propagation equation into the Euler equation to obtain the wave velocity equations of the sound pressure signal in the X-axis direction and the Y-axis direction; based on the pressure equations, the wave velocity equations, and the wave number equation, determining the expression of the wave number and the inner surface acoustic impedance, which is used to calculate the wave number loss factor according to the inner surface acoustic impedance.

[0008] The measurement method of material acoustic parameters provided by the embodiments of the present invention, simplifying the propagation equation to obtain the pressure equations of the sound pressure signal in the X-axis direction and the Y-axis direction without the time variable, includes: ; wherein, represents the pressure of the sound pressure signal in the X-axis direction, represents the pressure of the sound pressure signal in the Y-axis direction, x and y respectively represent the distance values of the sound pressure signal in the corresponding axis directions, and respectively represent the sound amplitudes of the sound pressure signal in the corresponding axis directions, and respectively represent the sound mode numbers of the sound pressure signal in the corresponding axis directions, and respectively represent the dimensions of the impedance tube in the corresponding axis directions.

[0009] The measurement method of material acoustic parameters provided by the embodiments of the present invention, based on the wave velocity equation, the pressure equation, and the wave number equation, determining the expression of the wave number and the inner surface acoustic impedance, includes: The wave number equation is: ; The expression is: ; ; wherein, respectively represent the wave numbers in the Z-axis direction, the X-axis direction, and the Y-axis direction, k represents the wave number of the impedance tube, and respectively represent the sound mode numbers of the sound pressure signal in the corresponding axis directions, and respectively represent the dimensions of the impedance tube in the corresponding axis directions, represents the acoustic impedance of the inner surface, represents the frequency of the sound pressure signal, represents the speed of sound in air, represents the wall diameter of the impedance tube, represents the air density.

[0010] The measurement method of the acoustic parameters of the material provided by the embodiment of the present invention creates is based on an iterative algorithm, and calculates the actual wave number of the impedance tube based on the wave number loss factor, including: determining the wave number to be iterated based on the theoretical wave number and the wave number loss factor; using the wave number to be iterated as the initial value, and performing iterative calculation on the following formula based on the Newton iterative method: ; wherein, represents the sound reflection coefficient, represents the transfer function, j represents the imaginary unit, k represents the wave number of the impedance tube, and respectively represent the first measurement position and the second measurement position of the sound pressure signal; the wave number of the impedance tube obtained after reaching the preset number of iterations is used as the actual wave number of the impedance tube.

[0011] The measurement method of the acoustic parameters of the material provided by the embodiment of the present invention creates calculates the acoustic parameters of the material to be measured based on geometric parameters, sound pressure signals, and actual wave numbers, including: calculating the transfer function based on the sound pressure signal; calculating the reflection coefficient and acoustic impedance of the material to be measured based on the actual wave number, transfer function, and geometric parameters; calculating the sound absorption coefficient of the material to be measured based on the acoustic impedance of the material to be measured; wherein, the acoustic parameters include the reflection coefficient, acoustic impedance, and sound absorption coefficient of the material to be measured.

[0012] The measurement method of the acoustic parameters of the material provided by the embodiment of the present invention creates obtains the geometric parameters of the impedance tube, the actual sound absorption coefficient, and the sound pressure signal propagating in the impedance tube, including: measuring the geometric parameters and the actual sound absorption coefficient of the impedance tube; tightly fixing the material to be measured at the end of the test end of the impedance tube; setting a loudspeaker at the other end of the impedance tube, wherein the loudspeaker is used to generate a sound pressure signal; arranging a microphone along the axial direction of the impedance tube; obtaining the sound pressure signal based on the microphone.

[0013] The measurement method of material acoustic parameters provided by the embodiments of the present invention creates a microphone is arranged along the axial direction of the impedance tube, including: arranging a first microphone and a second microphone along the axial direction of the impedance tube, wherein the first microphone is located between the speaker and the material to be measured, and the distance between the first microphone and the material to be measured is a first preset distance, the second microphone is located between the speaker and the first microphone, and the distance between the second microphone and the first microphone is a second preset distance; or, arranging a first microphone, a second microphone, a third microphone and a fourth microphone along the axial direction of the impedance tube, wherein the third microphone is located between the speaker and the second microphone, and the distance between the third microphone and the second microphone is a second preset distance, the fourth microphone is located between the speaker and the third microphone, and the distance between the fourth microphone and the third microphone is a third preset distance, and the third preset distance is greater than the second preset distance.

[0014] An electronic device provided by the embodiments of the present invention creates includes: a processor, and a memory storing a program, the program includes instructions, and when the instructions are executed by the processor, the processor executes any of the above methods.

[0015] A non-transitory machine-readable medium storing computer instructions provided by the embodiments of the present invention creates, the computer instructions are used to make a computer execute any of the above methods.

[0016] The measurement method of material acoustic parameters provided by the embodiments of the present invention creates obtains the flow resistivity of the inner tube wall and the corresponding simulated sound absorption coefficient by constructing an empty tube simulation model of the impedance tube. When the simulated sound absorption coefficient is close to the actual sound absorption coefficient, the corresponding flow resistivity of the inner tube wall is used as the simulated flow resistivity, so as to simulate and obtain an accurate inner surface acoustic impedance, and then obtain an accurate wave number loss factor. Combining with the iterative algorithm, a more accurate actual wave number can be calculated. Even when the impedance tube wall is non-rigid and the wave number loss is large, the internal loss of the impedance tube can be effectively corrected, thereby improving the measurement accuracy of material acoustic parameters. To solve the problem that the internal loss of the impedance tube in the related technology cannot be accurately corrected, resulting in low accuracy when measuring material acoustic parameters. Description of the Drawings

[0017] In order to more clearly illustrate the embodiments of the present invention creates or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention creates. For those of ordinary skill in the art, without creative efforts, other embodiments can be obtained based on these drawings.

[0018] Figure 1 It is a flowchart of the steps of a measurement method of material acoustic parameters in the embodiments of the present invention creates.

[0019] Figure 2 It is a schematic diagram of the actual sound absorption coefficient of the impedance tube in the embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of the simulated sound absorption coefficient obtained by simulation in the embodiment of the present invention.

[0021] Figure 4 It is a schematic diagram of the space rectangular coordinate system in the embodiment of the present invention.

[0022] Figure 5 It is a schematic diagram of the sound pressure signal measurement position in the embodiment of the present invention.

[0023] Figure 6 It is a schematic diagram of the structure of an electronic device in the embodiment of the present invention. Detailed implementation manners

[0024] The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to more thoroughly and completely understand the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not used to limit the protection scope of the present invention.

[0025] Related methods for calibrating the impedance tube: One is microphone phase error correction; the other is wave number transmission loss correction. Microphone phase error correction can be divided into reciprocal calibration and synchronous calibration, both of which correct the error caused by the microphone by normalizing the signal received by the microphone, but cannot correct the loss inside the impedance tube; the wave number transmission loss correction believes that the standard wave number theory attenuation formula underestimates the actual attenuation loss inside the impedance tube. By assuming that the reflection coefficient R = 1 at the rigid wall end and iterating the theoretical attenuation value of the wave number to approach the true value, but in the case where the impedance tube wall is non-rigid and the wave number loss is large, iteratively correcting with the theoretical attenuation value of the wave number often cannot obtain the correct loss inside the impedance tube.

[0026] For this reason, please refer to Figure 1 As shown, the embodiment of the present invention provides a method for measuring the acoustic parameters of a material, including steps S101 to S105.

[0027] Step S101, obtain the geometric parameters of the impedance tube, the actual sound absorption coefficient, and the sound pressure signal propagating in the impedance tube, where the impedance tube is used to measure the acoustic parameters of the material to be measured.

[0028] Step S102: Based on the geometric parameters, construct an empty-tube simulation model of the impedance tube to obtain the flow resistivity of the inner tube wall of the impedance tube and the corresponding simulated sound absorption coefficient. Among them, when the difference between the simulated sound absorption coefficient and the actual sound absorption coefficient is less than or equal to the preset threshold, the corresponding flow resistivity of the inner tube wall is used as the simulated flow resistivity.

[0029] Step S103: Based on the simulated flow resistivity, simulate the acoustic impedance of the inner surface of the impedance tube to calculate the wave number loss factor of the impedance tube.

[0030] Step S104: Based on the iterative algorithm and the wave number loss factor, calculate the actual wave number of the impedance tube.

[0031] Step S105: Based on the geometric parameters, the sound pressure signal, and the actual wave number, calculate the acoustic parameters of the material to be measured.

[0032] The geometric parameters of the impedance tube include but are not limited to the tube diameter, tube length, and cross-sectional shape.

[0033] The sound absorption coefficient is an important index to measure the sound absorption performance of materials or structures, and is defined as the ratio of the sound energy absorbed by the material or structure to the total sound energy incident on the material or structure.

[0034] The sound pressure signal propagating in the impedance tube is generated by the loudspeaker. The specific positions of the impedance tube, the loudspeaker, and the microphone will be introduced later and will not be elaborated here.

[0035] Constructing an empty-tube simulation model means simulating and modeling the sound field in the impedance tube without placing any test samples.

[0036] The flow resistivity cannot be directly measured, but through parametric scanning with simulation software, the flow resistivity of the inner tube wall of the impedance tube and the corresponding simulated sound absorption coefficient can be obtained, thereby reducing the measurement difficulty and facilitating the subsequent correction of the loss inside the impedance tube.

[0037] Exemplarily, the above simulation software is any one of COMSOL, ANSYS, ABAQUS, and SolidWorks Simulation. Those skilled in the art can select according to the actual situation, or can also use other software with similar functions for simulation.

[0038] Since the flow resistivity of the inner tube wall obtained by simulation may be quite different from the actual flow resistivity of the impedance tube, it is judged by the difference between the simulated sound absorption coefficient corresponding to the flow resistivity of the inner tube wall and the actual sound absorption coefficient of the impedance tube.

[0039] It can be understood that the flow resistivity and the sound absorption coefficient are directly related. When the difference between the simulated sound absorption coefficient and the actual sound absorption coefficient is less than or equal to a preset threshold, that is, when the difference is small, the gap between the flow resistivity of the inner pipe wall and the actual flow resistivity is small. Taking the above-mentioned flow resistivity of the inner pipe wall as the simulated flow resistivity can obtain a more accurate inner surface acoustic impedance, thereby obtaining a more accurate wave number loss factor and improving the accuracy of the correction of the in-tube loss.

[0040] The above preset threshold can be any number in the range of 0.05 - 0.1, and those skilled in the art can also determine the specific value of the above preset threshold according to prior values and actual situations.

[0041] The in-tube losses of the impedance tube include but are not limited to: medium loss, reflection loss, radiation loss, wall absorption loss, and local resistance loss. Among them, the loss caused by the wall absorption effect accounts for a relatively large proportion.

[0042] This embodiment mainly corrects the wall absorption loss of the impedance tube, and the wall of the impedance tube needs to be set to have a sound absorption effect during simulation.

[0043] It can be understood that using simulation software can reduce the measurement difficulty and correction difficulty of the in-tube loss of the impedance tube, but it is impossible to directly obtain all the in-tube losses of the impedance tube through the simulation software.

[0044] When the related technology corrects the in-tube loss of the impedance tube, it measures the sum of all acoustic parameters in the impedance tube, resulting in an increase in both the measurement difficulty and the correction difficulty. In the case where the impedance tube is a non-rigid impedance tube, such as a plastic impedance tube, a rubber impedance tube, or a foam impedance tube, the measurement difficulty and the correction difficulty will further increase. Even for a wooden impedance tube with a certain stiffness, it is very difficult for the related technology to accurately measure and correct the in-tube loss.

[0045] This embodiment uses simulation software and corrects the wall absorption loss. While reducing the measurement difficulty and the correction difficulty, it can ensure a certain correction accuracy by constructing the relationship between the simulated flow resistivity - inner surface acoustic impedance - wave number loss factor. On this basis, the accuracy of the correction of the in-tube loss of the impedance tube can be further improved through an iterative algorithm, thereby improving the measurement accuracy of the material acoustic parameters.

[0046] The iterative algorithm includes but is not limited to: Newton's iterative method, bisection method, secant method, fixed-point iterative method. Considering that the gap between the simulated flow resistivity and the actual flow resistivity obtained in this embodiment is small, and the obtained wave number loss factor is relatively close to the actual loss, and the closer the initial value of Newton's iterative method is to the actual solution, the better its iterative effect. Therefore, this embodiment preferably uses Newton's iterative method, takes the wave number to be iterated determined based on the theoretical wave number and the wave number loss factor as the initial value, and will be specifically introduced later.

[0047] It is understandable that the acoustic parameters of the material to be measured include, but are not limited to, the reflection coefficient, acoustic impedance, and sound absorption coefficient.

[0048] In summary, a method for measuring the acoustic parameters of a material provided by an embodiment of the present invention creates a simulation model of an empty impedance tube to obtain the flow resistivity of the inner tube wall and the corresponding simulated sound absorption coefficient. When the simulated sound absorption coefficient is close to the actual sound absorption coefficient, the corresponding flow resistivity of the inner tube wall is used as the simulated flow resistivity, thereby accurately simulating the inner surface acoustic impedance, and then obtaining the accurate wave number loss factor. Combining with the iterative algorithm can calculate a more accurate actual wave number. Even when the impedance tube wall is non-rigid and the wave number loss is large, it can effectively correct the internal loss of the impedance tube, thereby improving the measurement accuracy of the material acoustic parameters. This solves the problem in the related art that the internal loss of the impedance tube cannot be accurately corrected, resulting in low accuracy when measuring the acoustic parameters of the material.

[0049] Optionally, step S101 of obtaining the geometric parameters of the impedance tube, the actual sound absorption coefficient, and the sound pressure signal propagating in the impedance tube includes steps S1011 to S1015.

[0050] Step S1011, measure the geometric parameters and the actual sound absorption coefficient of the impedance tube.

[0051] Step S1012, tightly fix the material to be measured at the end of the test end of the impedance tube.

[0052] Step S1013, set a loudspeaker at the other end of the impedance tube, where the loudspeaker is used to generate a sound pressure signal.

[0053] Step S1014, set a microphone along the axial direction of the impedance tube.

[0054] A microphone is a device that converts a sound signal into an electrical signal, and a microphone is a common type of microphone.

[0055] Step S1015, obtain the sound pressure signal based on the microphone.

[0056] The sound pressure signal is a signal that describes the pressure change when a sound wave propagates in a medium, and contains the amplitude information, frequency information, phase information, time information, and waveform information of the sound wave.

[0057] It is understandable that obtaining accurate above-mentioned geometric parameters, actual sound absorption coefficient, and sound pressure signal helps to improve the accuracy of subsequent internal loss correction of the tube. Those skilled in the art can also use other methods to obtain the geometric parameters of the impedance tube, the actual sound absorption coefficient, and the sound pressure signal propagating in the impedance tube.

[0058] Preferably, in step S1014, arranging microphones along the axial direction of the impedance tube includes: arranging a first microphone and a second microphone along the axial direction of the impedance tube, where the first microphone is located between the speaker and the material to be measured, and the distance between the first microphone and the material to be measured is a first preset distance, and the second microphone is located between the speaker and the first microphone, and the distance between the second microphone and the first microphone is a second preset distance.

[0059] Among them, in order to avoid phase ambiguity or spatial aliasing, the second preset distance needs to be less than half of the wavelength corresponding to the highest test frequency. In order to avoid the near-field effect, the first preset distance needs to be greater than or equal to twice the second preset distance.

[0060] Furthermore, arrange a first microphone, a second microphone, a third microphone and a fourth microphone along the axial direction of the impedance tube, where the third microphone is located between the speaker and the second microphone, and the distance between the third microphone and the second microphone is the second preset distance, and the fourth microphone is located between the speaker and the third microphone, and the distance between the fourth microphone and the third microphone is a third preset distance, and the third preset distance is greater than the second preset distance.

[0061] It can be understood that the third preset distance being greater than the second preset distance can reduce the influence of spatial aliasing. The four-microphone method has higher measurement accuracy than the two-microphone method, has stronger sound field adaptability, and can obtain more acoustic parameters.

[0062] Specifically, in step S102, construct an empty-tube simulation model of the impedance tube based on geometric parameters to obtain the flow resistivity of the inner tube wall of the impedance tube and the corresponding simulated sound absorption coefficient.

[0063] When the difference between the simulated sound absorption coefficient and the actual sound absorption coefficient is less than or equal to the preset threshold, use the corresponding flow resistivity of the inner tube wall as the simulated flow resistivity.

[0064] When the difference between the simulated sound absorption coefficient and the actual sound absorption coefficient is greater than the preset threshold, adjust the boundary condition settings, solution settings, and post-processing settings of the above empty-tube simulation model to obtain a new simulated sound absorption coefficient until the difference between the new simulated sound absorption coefficient and the actual sound absorption coefficient is less than or equal to the preset threshold.

[0065] Exemplarily, referring to Figure 2 shows the actual sound absorption coefficient of the impedance tube, Figure 3 shows the simulated sound absorption coefficient obtained according to the empty-tube simulation model of the impedance tube, compare the difference between the two with the preset threshold, and use the flow resistivity of the inner tube wall corresponding to the simulated sound absorption coefficient whose difference is less than or equal to the preset threshold at the corresponding frequency as the simulated flow resistivity.

[0066] Preferably, after obtaining the inner surface acoustic impedance of the impedance tube by simulating the flow resistivity in step S103, the above method further includes steps S1031 to S1035.

[0067] In step S1031, please refer to Figure 4 As shown, a spatial rectangular coordinate system XYZ is established with the cross-sectional center of one end of the impedance tube as the coordinate origin, and the wave equation of the sound pressure signal is determined, where the Z-axis direction is the propagation direction of the sound pressure signal along the impedance tube.

[0068] The wave equation is: ; where p represents the sound pressure signal, x, y, and z respectively represent the distance values of the sound pressure signal in the corresponding axis directions, c represents the sound speed of the sound pressure signal in the tube, and t represents time.

[0069] In step S1032, the wave equation is separated by variables to obtain the propagation equations of the sound pressure signal in the corresponding axis directions containing the time variable, specifically as shown in the following formulas: ; ; where , , respectively represent the sound pressure of the sound pressure signal in the corresponding axis directions, e represents the natural constant, i represents the imaginary unit, f represents the frequency of the sound pressure signal, represents pi.

[0070] In step S1033, the propagation equations are simplified to obtain the pressure equations of the sound pressure signal in the X-axis and Y-axis directions without the time variable, specifically: ; where represents the sound pressure of the sound pressure signal in the X-axis direction, represents the sound pressure of the sound pressure signal in the Y-axis direction, and respectively represent the sound amplitudes of the sound pressure signal in the corresponding axis directions, and respectively represent the sound mode numbers of the sound pressure signal in the corresponding axis directions, and respectively represent the dimensions of the impedance tube in the corresponding axis directions.

[0071] In this embodiment, the pressure equation of the sound pressure signal in the Z-axis direction is also given here: ; where Indicates the pressure of the sound pressure signal in the Z-axis direction. Represents the acoustic amplitude of the sound pressure signal in the Z-axis direction, Indicates the wave number in the Z-axis direction.

[0072] Step S1034, substituting the propagation equation into the Euler equation to obtain the wave velocity equation of the sound pressure signal in the X-axis direction and the Y-axis direction.

[0073] The Euler equation is: ; The wave velocity equation of the sound pressure signal in the X-axis direction and the Y-axis direction is: ; ; in, represents the air density, and They respectively represent the wave velocity of the sound pressure signal in the corresponding axis direction.

[0074] Step S1035, based on the wave velocity equation, the pressure equation, and the wave number equation, determine the expression of the wave number and the inner surface acoustic impedance, which is used to calculate the wave number loss factor according to the inner surface acoustic impedance.

[0075] The wave number equation is: ; in, They represent the wave numbers in the Z-axis direction, X-axis direction, and Y-axis direction respectively, and k represents the wave number of the impedance tube.

[0076] based on Combining the wave velocity equation with the pressure equation, we get: ; ; in, represents the inner surface acoustic impedance, Indicates pressure, represents the wave speed, Indicates wavelength.

[0077] Combining the above wave number equation, the expression of wave number and inner surface acoustic impedance is obtained as follows: ; ; in, is the air speed of sound, Indicates the wall diameter of the impedance tube.

[0078] According to the inner surface acoustic impedance Obtain the wavenumber loss factor .

[0079] Preferably, in step S104, based on the iterative algorithm and the wavenumber loss factor, calculate the actual wavenumber of the impedance tube, including steps S1041 to S1043.

[0080] Step S1041, determine the wavenumber to be iterated based on the theoretical wavenumber and the wavenumber loss factor.

[0081] When the theoretical wavenumber is , the wavenumber to be iterated is .

[0082] When the theoretical wavenumber is k 实 +i*k 虚 , the wavenumber to be iterated is k 实 +i*k 虚 .

[0083] Step S1042, use the wavenumber to be iterated as the initial value of the solution of k, and perform iterative calculation on the following formula based on the Newton iteration method: ; wherein, represents the sound reflection coefficient, represents the transfer function, j represents the imaginary unit, k represents the wavenumber of the impedance tube, and respectively represent the first measurement position and the second measurement position of the sound pressure signal.

[0084] It can be understood that the transfer function is calculated according to the sound pressure signal.

[0085] Exemplarily, please refer to Figure 5 shown, the first measurement position represents the distance from the microphone 1 to the sample to be measured, and the second measurement position represents the distance from the microphone 2 to the sample to be measured.

[0086] In combination with the preferred embodiment of the above step S1014, the microphone 1 is the above-mentioned second microphone, the microphone 2 is the above-mentioned first microphone, the first measurement position is the sum of the above-mentioned first preset distance and the above-mentioned second preset distance, and the second measurement position is the above-mentioned first preset distance.

[0087] Step S1043, use the wavenumber of the impedance tube obtained after reaching the preset number of iterations as the actual wavenumber of the impedance tube.

[0088] It can be understood that the larger the value of the preset number of iterations, the closer the wavenumber of the impedance tube obtained by iteration is to the true wavenumber of the impedance tube, that is, the more accurate the above actual wavenumber is.

[0089] Since the simulated flow resistivity obtained in this embodiment is close to the actual flow resistivity, the inner surface acoustic impedance obtained by simulation is close to the actual inner surface acoustic impedance of the impedance tube. Therefore, the wavenumber loss factor calculated based on the inner surface acoustic impedance obtained by simulation is close to the actual loss of the impedance tube, making the wavenumber to be iterated determined based on the wavenumber loss factor close to the true wavenumber of the impedance tube, that is, the above initial value is close to the true solution of k. Therefore, even when the preset number of iterations is small, the wavenumber of the impedance tube obtained by iteration is also close enough to the true wavenumber of the impedance tube, that is, the above actual wavenumber is accurate enough.

[0090] In other words, by setting a reasonable preset number of iterations, accurate actual wavenumbers can be obtained while saving computational effort and reducing computational time. Those skilled in the art can determine a reasonable preset number of iterations based on prior values and actual situations.

[0091] Preferably, in step S105, based on the geometric parameters, acoustic pressure signal, and actual wavenumber, calculate the acoustic parameters of the material to be measured, including steps S1051 to S1053.

[0092] Step S1051, calculate the transfer function based on the acoustic pressure signal.

[0093] Step S1052, calculate the reflection coefficient and acoustic impedance of the material to be measured based on the actual wavenumber, transfer function, and geometric parameters.

[0094] Step S1053, calculate the sound absorption coefficient of the material to be measured based on the acoustic impedance of the material to be measured.

[0095] Among them, the acoustic parameters include the reflection coefficient, acoustic impedance, and sound absorption coefficient of the material to be measured.

[0096] It can be understood that the above actual wavenumber is the wavenumber after accurately correcting the loss inside the impedance tube, and the acoustic parameters of the material to be measured calculated therefrom are highly accurate.

[0097] Those skilled in the art can calculate acoustic parameters other than the reflection coefficient, acoustic impedance, and sound absorption coefficient of the material to be measured based on the measured geometric parameters of the impedance tube, acoustic pressure signal, and the above actual wavenumber obtained by iteration. This embodiment will not elaborate herein.

[0098] In summary, the greater the loss caused by the impedance tube wall, the more obvious the improvement of the measurement accuracy by the method provided in this embodiment. The above method obtains the wave number loss factor through theoretical calculation and makes it closer to the actual value through iteration. It can be applied even when the impedance tube wall is not rigid. On the one hand, it has high universality and convenience. On the other hand, it does not require the impedance tube wall to be strictly rigid, so there is no need to lay rigid materials inside the impedance tube wall, thus greatly saving the manufacturing cost of the impedance tube, especially saving the manufacturing cost of large-volume impedance tubes.

[0099] An embodiment of the present invention also provides a non-transitory machine-readable medium storing a computer program, wherein the above computer program, when executed by a processor of a computer, is used to cause the computer to execute the method of the embodiment of the present invention.

[0100] An embodiment of the present invention also provides a computer program product, including a computer program, wherein the computer program, when executed by a processor of a computer, is used to cause the computer to execute the method of the embodiment of the present invention.

[0101] An embodiment of the present invention also provides an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor. The above memory stores a computer program capable of being executed by the at least one processor, and the above computer program, when executed by the at least one processor, is used to cause the electronic device to execute the method of the embodiment of the present invention.

[0102] Reference Figure 6 , the structural block diagram of an electronic device that can be used as a server or a client in an embodiment of the present invention will now be described. It is an example of a hardware device that can be applied to various aspects of the present invention. The electronic device is intended to represent various forms of digital electronic computer devices, such as, laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as, personal digital processors, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or claimed herein.

[0103] As Figure 6As shown, the electronic device includes a computing unit 601, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 602 or a computer program loaded from a storage unit 608 into a random access memory (RAM) 603. In the RAM 603, various programs and data required for the operation of the electronic device can also be stored. The computing unit 601, the ROM 602, and the RAM 603 are connected to each other via a bus 604. An input / output (I / O) interface 605 is also connected to the bus 604.

[0104] Multiple components in the electronic device are connected to the I / O interface 605, including: an input unit 606, an output unit 607, a storage unit 608, and a communication unit 609. The input unit 606 can be any type of device capable of inputting information into the electronic device. The input unit 606 can receive input digital or character information and generate key signal inputs related to the user settings and / or function controls of the electronic device. The output unit 607 can be any type of device capable of presenting information and can include, but is not limited to, a display, a speaker, a video / audio output terminal, a vibrator, and / or a printer. The storage unit 608 can include, but is not limited to, magnetic disks and optical discs. The communication unit 609 allows the electronic device to exchange information / data with other devices via a computer network such as the Internet and / or various telecommunication networks and can include, but is not limited to, a modem, a network card, an infrared communication device, and / or a wireless communication transceiver, such as a Bluetooth device, a WiFi device, a WiMax device, a cellular communication device, and / or the like.

[0105] The computing unit 601 can be various general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 601 include, but are not limited to, a CPU, a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing units, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The computing unit 601 executes the various methods and processes described above. For example, in some embodiments, the method embodiments of the present invention can be implemented as a computer program tangibly embodied in a machine-readable medium, such as the storage unit 608. In some embodiments, part or all of the computer program can be loaded and / or installed onto the electronic device via the ROM 602 and / or the communication unit 609. In some embodiments, the computing unit 601 can be configured to execute the above methods in any other appropriate manner (e.g., by means of firmware).

[0106] The computer program for implementing the method of the embodiment of the present invention can be written in any combination of one or more programming languages. These computer programs can be provided to the processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing devices, so that when the computer programs are executed by the processor or controller, the functions / operations specified in the flowchart and / or block diagram are implemented. The computer programs can be executed entirely on the machine, partially on the machine, executed partially on the machine and partially on a remote machine as an independent software package, or executed entirely on a remote machine or server.

[0107] In the context of the embodiment of the present invention, a machine-readable medium can be a tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable signal medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, or infrared system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0108] It should be noted that the term "including" and its variants used in the embodiments of the present invention are open-ended, that is, "including but not limited to". The term "based on" is "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "a plurality" mentioned in the embodiments of the present invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise clearly specified in the context, it should be understood as "one or more". The descriptions of the terms "first", "second", etc. are only for descriptive purposes and should not be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features.

[0109] The user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the embodiments of the present invention are all information and data that have been authorized by the user or fully authorized by all parties. And the collection, use, and processing of the relevant data need to comply with the relevant laws, regulations, and standards of the relevant countries and regions, and corresponding operation entrances are provided for the user to select to authorize or refuse.

[0110] In the method embodiments provided by the embodiments of the present invention, the steps described can be executed in different orders and / or executed in parallel. In addition, the method embodiments may include additional steps and / or omit the steps shown. The protection scope of the present invention is not limited in this regard.

[0111] The term "embodiment" in this specification means that the specific features, structures or characteristics described in connection with the embodiments may be included in at least one embodiment of the present invention. The phrase appears in various positions in the specification and does not necessarily mean the same embodiment, nor does it mean being independent or alternative to other embodiments and mutually exclusive. The various embodiments in this specification are described in a related manner, and the same or similar parts between the embodiments are referred to each other. In particular, for device, equipment, and system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and the relevant parts refer to the partial description of the method embodiments.

[0112] The above-described embodiments merely represent several implementation manners of the present invention, and the description is relatively specific and detailed, but should not be construed as a limitation on the protection scope. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for measuring the acoustic parameters of a material, characterized in that, Including: Obtaining the geometric parameters of the impedance tube, the actual absorption coefficient, and the sound pressure signal propagating in the impedance tube, where the impedance tube is used to measure the acoustic parameters of the material to be measured; Based on the geometric parameters, constructing an empty tube simulation model of the impedance tube to obtain the flow resistivity of the inner tube wall of the impedance tube and the corresponding simulated absorption coefficient, where when the difference between the simulated absorption coefficient and the actual absorption coefficient is less than or equal to a preset threshold, the corresponding flow resistivity of the inner tube wall is used as the simulated flow resistivity; Based on the simulated flow resistivity, simulating the acoustic impedance of the inner surface of the impedance tube to calculate the wave number loss factor of the impedance tube; Based on the iterative algorithm and the wave number loss factor, calculating the actual wave number of the impedance tube; Based on the geometric parameters, the sound pressure signal, and the actual wave number, calculating the acoustic parameters of the material to be measured.

2. The method according to claim 1, characterized in that, After simulating the acoustic impedance of the inner surface of the impedance tube based on the simulated flow resistivity, the method further includes: Establishing a space rectangular coordinate system XYZ with the cross-sectional center of one end of the impedance tube as the coordinate origin, and determining the wave equation of the sound pressure signal, where the Z-axis direction is the propagation direction of the sound pressure signal along the impedance tube; Performing variable separation processing on the wave equation to obtain the propagation equation containing the time variable of the sound pressure signal in the corresponding axis direction; Simplifying the propagation equation to obtain the pressure equations of the sound pressure signal in the X-axis direction and the Y-axis direction without the time variable; Substituting the propagation equation into Euler's equation to obtain the wave speed equations of the sound pressure signal in the X-axis direction and the Y-axis direction; Based on the pressure equation, the wave speed equation, and the wave number equation, determining the expression of the wave number and the inner surface acoustic impedance, which is used to calculate the wave number loss factor according to the inner surface acoustic impedance.

3. The method according to claim 2, wherein Simplifying the propagation equation to obtain the pressure equations of the sound pressure signal in the X-axis direction and the Y-axis direction without the time variable, including: ； wherein, represents the sound pressure of the sound pressure signal in the X-axis direction, represents the sound pressure of the sound pressure signal in the Y-axis direction, and x and y respectively represent the distance values of the sound pressure signal in the corresponding axis directions, and respectively represent the sound amplitudes of the sound pressure signal in the corresponding axis directions, and respectively represent the sound mode numbers of the sound pressure signal in the corresponding axis directions, and respectively represent the dimensions of the impedance tube in the corresponding axis directions.

4. The method according to claim 2, wherein Based on the wave speed equation, the pressure equation, and the wave number equation, determining the expression of the wave number and the inner surface acoustic impedance, including: The wave number equation is: ； The expression is: ； ； Among them, respectively represent the wavenumbers in the Z-axis direction, X-axis direction, and Y-axis direction, k represents the wavenumber of the impedance tube, and respectively represent the acoustic mode numbers of the sound pressure signal in the corresponding axis directions, and respectively represent the dimensions of the impedance tube in the corresponding axis directions, represents the inner surface acoustic impedance, represents the frequency of the sound pressure signal, represents the speed of sound in air, represents the wall diameter of the impedance tube, represents the air density.

5. The method according to claim 1, characterized in that Based on the iterative algorithm and the wave number loss factor, calculating the actual wave number of the impedance tube, including: Determining the wave number to be iterated based on the theoretical wave number and the wave number loss factor; Taking the wave number to be iterated as the initial value and performing iterative calculation on the following formula based on Newton's iterative method: ； wherein, represents the acoustic reflection coefficient, represents the transfer function, j represents the imaginary unit, and k represents the wave number of the impedance tube, and respectively represent the first measurement position and the second measurement position of the sound pressure signal; Taking the wave number of the impedance tube obtained after reaching the preset number of iterations as the actual wave number of the impedance tube.

6. The method according to claim 1, characterized in that Based on the geometric parameters, the sound pressure signal, and the actual wave number, calculating the acoustic parameters of the material to be measured, including: Calculating the transfer function based on the sound pressure signal; Based on the actual wave number, the transfer function, and the geometric parameters, calculating the reflection coefficient and acoustic impedance of the material to be measured; Calculating the absorption coefficient of the material to be measured based on the acoustic impedance of the material to be measured; Wherein, the acoustic parameters include the reflection coefficient, acoustic impedance, and absorption coefficient of the material to be measured.

7. The method according to claim 1, characterized in that Obtaining the geometric parameters of the impedance tube, the actual absorption coefficient, and the sound pressure signal propagating in the impedance tube, including: Measure the geometric parameters and actual sound absorption coefficient of the impedance tube; Tightly fix the material to be measured at the end of the test end of the impedance tube; Set a loudspeaker at the other end of the impedance tube, wherein the loudspeaker is used to generate the sound pressure signal; Set a microphone along the axial direction of the impedance tube; Obtain the sound pressure signal based on the microphone.

8. The method according to claim 7, characterized in that, Setting a microphone along the axial direction of the impedance tube includes: Setting a first microphone and a second microphone along the axial direction of the impedance tube, wherein the first microphone is located between the material to be measured and the loudspeaker, and the distance between the first microphone and the material to be measured is a first preset distance, the second microphone is located between the loudspeaker and the first microphone, and the distance between the second microphone and the first microphone is a second preset distance; Alternatively, the first microphone, the second microphone, a third microphone and a fourth microphone are arranged along the axial direction of the impedance tube, wherein the third microphone is located between the loudspeaker and the second microphone, and the distance between the third microphone and the second microphone is the second preset distance, the fourth microphone is located between the loudspeaker and the third microphone, and the distance between the fourth microphone and the third microphone is a third preset distance, and the third preset distance is greater than the second preset distance.

9. An electronic device, comprising: A processor and a memory storing a program, wherein the program includes instructions that, when executed by the processor, cause the processor to execute the method according to any one of claims 1 to 8.

10. A non-transitory machine-readable medium storing computer instructions, characterized in that, The computer instructions are used to cause the computer to execute the method according to any one of claims 1 to 8.

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