阅读说明：本技术 一种六传声器三维声强法吸声系数测量系统及其测量方法 (Six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system and measurement method thereof ) 是由 王红卫 於秀 熊威 于 2021-08-18 设计创作，主要内容包括：本发明公开了一种六传声器三维声强法吸声系数测量系统及其测量方法,该系统包括：PC机、声卡、功率放大器、正十二面体扬声器、吸声系数测量装置、六传声器三维声强探头、显示器、待测材料或构件、全反射板、不透声障板；PC机、功率放大器、正十二面体扬声器依次相连,构成发声模块,生成无指向性声波信号；吸声系数测量装置分别与六传声器三维声强探头、显示器连接,构成受声模块；发声模块和受声模块分别位于待测材料或构件的两侧,不透声障板设于发声模块和受声模块之间,遮挡正十二面体扬声器的直达声；全反射板与不透声障板垂直设置。本发明可根据材料实际安装的情况进行测量,既可在消声室中进行测量,也可在一般条件的场所进行测量。(The invention discloses a six-microphone three-dimensional sound intensity method sound absorption coefficient measuring system and a measuring method thereof, wherein the system comprises the following components: the device comprises a PC (personal computer), a sound card, a power amplifier, a regular dodecahedron loudspeaker, a sound absorption coefficient measuring device, a six-microphone three-dimensional sound intensity probe, a display, a material or component to be tested, a total reflection plate and an acoustic-proof baffle; the PC, the power amplifier and the regular dodecahedron loudspeaker are sequentially connected to form a sound production module to generate an omnidirectional sound wave signal; the sound absorption coefficient measuring device is respectively connected with the six-microphone three-dimensional sound intensity probe and the display to form a sound receiving module; the sound-proof baffle plate is arranged between the sound-producing module and the sound-receiving module and used for shielding direct sound of the regular dodecahedron loudspeaker; the total reflection plate is perpendicular to the sound-proof baffle. The invention can measure according to the actual installation condition of the material, not only in an anechoic chamber, but also in a place with general conditions.)

1. A six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system is characterized by comprising: the device comprises a PC (personal computer), a sound card, a power amplifier, a regular dodecahedron loudspeaker, a sound absorption coefficient measuring device, a six-microphone three-dimensional sound intensity probe, a display, a material or component to be tested, a total reflection plate and an acoustic-proof baffle;

the sound card is arranged in a PC (personal computer), the PC, the power amplifier and the regular dodecahedron loudspeaker are sequentially connected to form a sound production module, and the sound production module is used for generating an omnidirectional sound wave signal;

the sound absorption coefficient measuring device is respectively connected with the six-microphone three-dimensional sound intensity probe and the display to form a sound receiving module;

the sound-proof baffle plate is arranged between the sound-proof module and the sound-receiving module and used for shielding direct sound from the regular dodecahedron loudspeaker;

the total reflection plate is perpendicular to the sound-proof baffle.

2. The six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system according to claim 1, wherein the relative positions of the six microphone probes of the six-microphone three-dimensional sound intensity probe are arranged in a pairwise opposite manner to form a regular sphere in space.

3. The six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system according to claim 2, wherein a three-dimensional rectangular coordinate system is established with the geometric center of the regular sphere as an origin, two microphones are located on X, Y, Z coordinate axes, the distance from the origin of each microphone is the same, the radius R of the circumscribed sphere of the six microphone probes is, and the coordinates of the six microphones are (R, 0, 0), (-R, 0, 0), (0, R, 0), (0, -R, 0), (0, 0, R), (0, 0, -R), respectively.

4. The six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system according to claim 1, wherein the six-microphone three-dimensional sound intensity probe is disposed on a reflected sound line, the geometric center position of the six-microphone three-dimensional sound intensity probe is taken as an origin, the first microphone and the second microphone are taken as X-axes, the X-axes are parallel to the material or the member to be measured, the third microphone and the fourth microphone are taken as Y-axes, the Y-axes are perpendicular to the material or the member to be measured, and the fifth microphone and the sixth microphone are taken as Z-axes, the Z-axes are perpendicular to a horizontal plane;

the center of the regular dodecahedron loudspeaker and the geometric center of the six-microphone three-dimensional sound intensity probe are positioned on the same horizontal plane.

5. The measuring method of the six-microphone three-dimensional sound intensity method sound absorption coefficient measuring system according to any one of claims 1 to 4, characterized by comprising the steps of:

determining the external sphere radius of the six-microphone three-dimensional sound intensity probe according to the measurement frequency range of the sound absorption coefficient of the material to be measured;

determining the distance between the sound-proof baffle and the material or component to be measured according to the lowest frequency of the required measuring frequency range;

setting a measuring incident angle, and adjusting the linear distance between the regular dodecahedron loudspeaker and the material or the component to be measured;

carrying out first measurement, measuring the sound intensity at the geometric center position of a six-microphone three-dimensional sound intensity probe, sequentially sending noise signals of measured frequency by a regular dodecahedron loudspeaker, and receiving six-channel sound pressure signals by the six-microphone three-dimensional sound intensity probe;

the six-microphone three-dimensional sound intensity probe transmits the received sound pressure signal to the sound absorption coefficient measuring device to complete time domain display and three-dimensional sound intensity calculation of each channel signal;

taking the first microphone and the second microphone as X axes, parallel to the material or the component to be detected, taking the third microphone and the fourth microphone as Y axes, respectively carrying out cross-spectrum calculation on the sound pressure signals received by the first microphone and the second microphone, the sound pressure signals received by the third microphone and the fourth microphone, and the sound pressure signals received by the fifth microphone and the sixth microphone to obtain X, Y, Z axial sound intensity components which are respectively represented as I_1X(ω)、I_1Y(ω)、I_1Z(omega) to obtain the reflected sound intensity I after being reflected by the material or the component to be measured_r；

Placing sound-proof baffle plate or total reflection plate with same size and size at same position of material or component to be measured, making second measurement, using regular dodecahedron loudspeaker to successively give out noise signal with same frequency as that in first measurement, using six-microphone three-dimensional sound intensity probe to transfer the received sound pressure signal to sound absorption coefficient measuring device to implement time domain display and three-dimensional sound intensity calculation of all channel signals so as to obtain X, Y, Z three-directional sound intensity components respectively represented as I_2X(ω)、I_2Y(ω)、I_2Z(ω) and further the incident sound intensity I_i；

Incident sound intensity I at geometric center position of six-microphone probe based on measurement_iAnd reflected sound intensity I_rAnd calculating corresponding vector information to obtain a sound intensity reflection coefficient, and solving the sound absorption coefficient of the material according to the relation between the sound absorption coefficient and the sound intensity reflection coefficient.

6. The measuring method of the six-microphone three-dimensional sound intensity method sound absorption coefficient measuring system according to claim 5, further comprising the steps of measuring an incident angle and calculating an incident angle measurement error value, specifically:

the incident angle is averaged from the arctangent of the ratio of the X, Y-axis components of the first and second measurements of three-dimensional sound intensity, and is expressed as:

and measuring the incident angle theta 'between the sound source and the vertical central line of the material, and taking the absolute value of the difference value of the incident angle theta' and the vertical central line of the material to obtain an incident angle measurement error value.

7. The method for measuring the six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system according to claim 5, wherein the method for measuring the sound intensity at the geometric center position of the six-microphone three-dimensional sound intensity probe comprises the following specific steps:

approximate estimation by averaging sound pressure of each microphone, in time domain P₀(t) and in the frequency domain P₀(f) Respectively as follows:

wherein, P_i(t) an expression of sound pressure of each microphone in the time domain, P_i(f) An expression representing the sound pressure of each microphone in a frequency domain, wherein the subscript i represents the serial number of the microphone, and i is 1-6;

calculating the component U of the particle vibration speed at the geometric center position of the six-microphone three-dimensional sound intensity probe in the X, Y, Z axis direction_x、U_y、U_zSound pressure P to each microphone_iComprises the following steps:

wherein j is an imaginary unit, f is frequency, rho is air density, and R represents the external sphere radius of the six-microphone three-dimensional sound intensity probe.

8. The method as claimed in claim 5, wherein the X, Y, Z component is obtained by calculating the sound intensity in the direction of axis as I_1X(ω)、I_1Y(ω)、I_1Z(ω), the specific calculation formula is:

wherein G is₁₂Single-sided cross-power spectral function G representing sound pressures of first and second microphones₃₄Single-sided cross-power spectral function G representing sound pressures of third and fourth microphones₅₆The single-side cross-power spectral functions of sound pressures of a fifth microphone and a sixth microphone are represented, j is an imaginary number unit, f is frequency, rho is air density, R represents the external sphere radius of a three-dimensional sound intensity probe of the sixth microphone, and Im represents an imaginary part;

further obtaining the reflected sound intensity I after being reflected by the material or the component to be measured_rExpressed as:

9. the method as claimed in claim 5, wherein the X, Y, Z three-directional sound intensity components are represented as I_2X(ω)、I_2Y(ω)、I_2Z(ω), the specific calculation formula is:

wherein G is₁₂Single-sided cross-power spectral function G representing sound pressures of first and second microphones₃₄Single-sided cross-power spectral function G representing sound pressures of third and fourth microphones₅₆The single-side cross-power spectral functions of sound pressures of a fifth microphone and a sixth microphone are represented, j is an imaginary number unit, f is frequency, rho is air density, R represents the external sphere radius of a three-dimensional sound intensity probe of the sixth microphone, and Im represents an imaginary part;

incident sound intensity I_iExpressed as:

10. the measuring method of the six-microphone three-dimensional sound intensity method sound absorption coefficient measuring system according to claim 5, wherein the sound absorption coefficient of the material is obtained according to the relation between the sound absorption coefficient and the sound intensity reflection coefficient, and the specific calculation formula is as follows:

α(θ)＝1-R_I(θ)

wherein R is_I(theta) represents a sound intensity reflection coefficient, and alpha (theta) represents a sound absorption coefficient.

Technical Field

The invention relates to the technical field of sound absorption coefficient measurement, in particular to a six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system and a measurement method thereof.

Background

The sound absorption coefficient is an important parameter for measuring the acoustic characteristics of the material, so that the sound absorption coefficient of the material at each frequency is accurately measured, and the sound absorption coefficient has an important influence on the reasonable use of various sound absorption materials or sound absorption structures in a building space. At present, laboratory methods for measuring sound absorption coefficients mainly include an impedance tube method and a reverberation chamber method. Both methods need to measure the sound absorption coefficient of a material or a structure in a laboratory, and in practical application, the field environmental conditions often cannot meet the measurement environmental requirements of the laboratory, and the size and the installation condition of the material are closely related to the sound absorption coefficient. Therefore, in practical applications, a measurement method capable of measuring more accurately on site and reflecting the sound absorption coefficient of a material or a structure during practical application and installation is needed.

The traditional sound intensity measurement technology mainly comprises a P-P method and a P-U method, and has the defect that the sound intensity in a single direction can only be obtained by one measurement, and if the sound intensity vector of a certain point needs to be determined, the measurement needs to be carried out at least 3 times. The three-dimensional sound intensity measurement technology is developed till now, and can realize one-time measurement to obtain sound intensity vectors in three directions. The sound intensity measurement technology can be applied to various fields such as sound power measurement, identification and positioning of noise sources, identification and sequencing of sound sources, sound insulation measurement and the like, and can also be applied to the field of sound absorption coefficient measurement.

Disclosure of Invention

The invention provides a six-microphone three-dimensional sound intensity method sound absorption coefficient measuring system and a measuring method thereof, aiming at overcoming the defects and shortcomings of the existing sound absorption coefficient measuring method that the requirement on the material is high and the sound absorption coefficient of the material under the actual installation condition cannot be measured, the invention is based on the three-dimensional sound intensity method, utilizes the vector characteristic of the sound intensity, calculates the sound intensity reflection coefficient by respectively measuring the incident sound intensity and the reflected sound intensity at the three-dimensional sound intensity probe of the six microphones and the vector information of the incident sound intensity and the reflected sound intensity, then obtains the sound absorption coefficient of the material according to the relation between the sound absorption coefficient and the sound intensity reflection coefficient, simultaneously calculates the incident angle and other information of the sound source by utilizing the vector information of the three-dimensional sound intensity, can immediately obtain the sound absorption coefficient and the sound source incident angle of the material under the measuring frequency after the signal acquisition is finished, and realizes the measurement of the sound absorption coefficient of the material under the oblique incident angle, the measurement is simple.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a six-microphone three-dimensional sound intensity method sound absorption coefficient measuring system, which comprises: the device comprises a PC (personal computer), a sound card, a power amplifier, a regular dodecahedron loudspeaker, a sound absorption coefficient measuring device, a six-microphone three-dimensional sound intensity probe, a display, a material or component to be tested, a total reflection plate and an acoustic-proof baffle;

the sound card is arranged in a PC (personal computer), the PC, the power amplifier and the regular dodecahedron loudspeaker are sequentially connected to form a sound production module, and the sound production module is used for generating an omnidirectional sound wave signal;

the sound absorption coefficient measuring device is respectively connected with the six-microphone three-dimensional sound intensity probe and the display to form a sound receiving module;

the sound-proof baffle plate is arranged between the sound-proof module and the sound-receiving module and used for shielding direct sound from the regular dodecahedron loudspeaker;

the total reflection plate is perpendicular to the sound-proof baffle.

Preferably, the relative positions of the six microphone probes of the six-microphone three-dimensional sound intensity probe are arranged in a form of facing each other two by two, and a regular sphere is formed in space.

As a preferred technical solution, a three-dimensional rectangular coordinate system is established with the geometric center of the said sphere as an origin, two microphones fall on X, Y, Z three coordinate axes, the distance from the origin to each microphone is the same, and is the circumscribed sphere radius R of the six microphone probes, and the coordinates of the six microphones are (R, 0, 0), (-R, 0, 0), (0, R, 0), (0, -R, 0), (0, 0, R), (0, 0, -R), respectively.

As a preferred technical scheme, the six-microphone three-dimensional sound intensity probe is arranged on a reflected sound line, the geometric central position of the six-microphone three-dimensional sound intensity probe is taken as an original point, the first microphone and the second microphone are taken as X axes and are parallel to a material or a component to be measured, the third microphone and the fourth microphone are taken as Y axes and are vertical to the material or the component to be measured, and the fifth microphone and the sixth microphone are taken as Z axes and are vertical to a horizontal plane;

the center of the regular dodecahedron loudspeaker and the geometric center of the six-microphone three-dimensional sound intensity probe are positioned on the same horizontal plane.

The invention also provides a measuring method of the six-microphone three-dimensional sound intensity method sound absorption coefficient measuring system, which comprises the following steps:

determining the external sphere radius of the six-microphone three-dimensional sound intensity probe according to the measurement frequency range of the sound absorption coefficient of the material to be measured;

determining the distance between the sound-proof baffle and the material or component to be measured according to the lowest frequency of the required measuring frequency range;

setting a measuring incident angle, and adjusting the linear distance between the regular dodecahedron loudspeaker and the material or the component to be measured;

carrying out first measurement, measuring the sound intensity at the geometric center position of a six-microphone three-dimensional sound intensity probe, sequentially sending noise signals of measured frequency by a regular dodecahedron loudspeaker, and receiving six-channel sound pressure signals by the six-microphone three-dimensional sound intensity probe;

the six-microphone three-dimensional sound intensity probe transmits the received sound pressure signal to the sound absorption coefficient measuring device to complete time domain display and three-dimensional sound intensity calculation of each channel signal;

taking the first microphone and the second microphone as X axes, parallel to the material or the component to be detected, taking the third microphone and the fourth microphone as Y axes, respectively carrying out cross-spectrum calculation on the sound pressure signals received by the first microphone and the second microphone, the sound pressure signals received by the third microphone and the fourth microphone, and the sound pressure signals received by the fifth microphone and the sixth microphone to obtain X, Y, Z axial sound intensity components which are respectively represented as I_1X(ω)、I_1Y(ω)、I_1Z(omega) to obtain the reflected sound intensity after being reflected by the material or the component to be measuredI_r；

Placing sound-proof baffle plate or total reflection plate with same size and size at same position of material or component to be measured, making second measurement, using regular dodecahedron loudspeaker to successively give out noise signal with same frequency as that in first measurement, using six-microphone three-dimensional sound intensity probe to transfer the received sound pressure signal to sound absorption coefficient measuring device to implement time domain display and three-dimensional sound intensity calculation of all channel signals so as to obtain X, Y, Z three-directional sound intensity components respectively represented as I_2X(ω)、I_2Y(ω)、I_2Z(ω) and further the incident sound intensity I_i；

Incident sound intensity I at geometric center position of six-microphone probe based on measurement_iAnd reflected sound intensity I_rAnd calculating corresponding vector information to obtain a sound intensity reflection coefficient, and solving the sound absorption coefficient of the material according to the relation between the sound absorption coefficient and the sound intensity reflection coefficient.

As a preferred technical solution, the method further comprises the steps of measuring the incident angle and calculating the incident angle measurement error value, specifically:

the incident angle is averaged from the arctangent of the ratio of the X, Y-axis components of the first and second measurements of three-dimensional sound intensity, and is expressed as:

and measuring the incident angle theta 'between the sound source and the vertical central line of the material, and taking the absolute value of the difference value of the incident angle theta' and the vertical central line of the material to obtain an incident angle measurement error value.

As a preferred technical solution, the measuring of the sound intensity at the geometric center position of the six-microphone three-dimensional sound intensity probe specifically includes the steps of:

approximate estimation by averaging sound pressure of each microphone, in time domain P₀(t) and in the frequency domain P₀(f) Respectively as follows:

wherein, P_i(t) an expression of sound pressure of each microphone in the time domain, P_i(f) An expression representing the sound pressure of each microphone in a frequency domain, wherein the subscript i represents the serial number of the microphone, and i is 1-6;

calculating the component U of the particle vibration speed at the geometric center position of the six-microphone three-dimensional sound intensity probe in the X, Y, Z axis direction_x、U_y、U_zSound pressure P to each microphone_iComprises the following steps:

wherein j is an imaginary unit, f is frequency, rho is air density, and R represents the external sphere radius of the six-microphone three-dimensional sound intensity probe.

Preferably, the obtained X, Y, Z axial sound intensity components are respectively represented as I_1X(ω)、I_1Y(ω)、I_1Z(ω), the specific calculation formula is:

wherein G is₁₂Single-sided cross-power spectral function G representing sound pressures of first and second microphones₃₄Single-sided cross-power spectral function G representing sound pressures of third and fourth microphones₅₆The single-side cross-power spectral functions of sound pressures of a fifth microphone and a sixth microphone are represented, j is an imaginary number unit, f is frequency, rho is air density, R represents the external sphere radius of a three-dimensional sound intensity probe of the sixth microphone, and Im represents an imaginary part;

further obtaining the reflected sound intensity I after being reflected by the material or the component to be measured_rExpressed as:

preferably, the obtained X, Y, Z three-directional sound intensity components are respectively represented as I_2X(ω)、I_2Y(ω)、I_2Z(ω), the specific calculation formula is:

wherein G is₁₂Single-sided cross-power spectral function G representing sound pressures of first and second microphones₃₄Single-sided cross-power spectral function G representing sound pressures of third and fourth microphones₅₆The single-side cross-power spectral functions of sound pressures of a fifth microphone and a sixth microphone are represented, j is an imaginary number unit, f is frequency, rho is air density, R represents the external sphere radius of a three-dimensional sound intensity probe of the sixth microphone, and Im represents an imaginary part;

incident sound intensity I_iExpressed as:

as a preferred technical scheme, the sound absorption coefficient of the material is obtained according to the relationship between the sound absorption coefficient and the sound intensity reflection coefficient, and the specific calculation formula is as follows:

α(θ)＝1-R_I(θ)

wherein R is_I(theta) represents a sound intensity reflection coefficient, and alpha (theta) represents a sound absorption coefficient.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the invention adopts a six-microphone three-dimensional sound intensity measurement technology, solves the technical problems that the laboratory measurement method of the sound absorption coefficient has higher requirements on the size and the like of the measured material, achieves the technical effect of measurement according to the actual installation condition of the material, and can be used for measurement in an anechoic chamber and in places with common conditions.

(2) The invention adopts a six-microphone three-dimensional sound intensity measurement technology, solves the technical problem that the conventional normal sound absorption coefficient and random incident sound absorption coefficient can only measure the sound absorption coefficient at a specific angle, realizes the measurement of the sound absorption coefficient of the material at any oblique incident angle, and has wider application.

(3) The invention adopts a six-microphone three-dimensional sound intensity measuring technology, measures the incident angle of a sound source by utilizing the vector information of the three-dimensional sound intensity while measuring the sound absorption coefficient, is beneficial to determining the direction of a main noise source in the actual engineering measurement, and can be applied to the actual situation that the incident angle from some sound source to a material or a structure is difficult to obtain.

Drawings

FIG. 1 is a schematic structural diagram of a six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system of the present invention;

FIG. 2 is a schematic structural diagram of a six-microphone three-dimensional sound intensity probe according to the present invention;

FIG. 3 is a schematic illustration of sound absorption coefficient measurements according to the present invention;

FIG. 4 is a diagram illustrating the measurement error of the incident angle according to the present invention.

The device comprises a PC (personal computer) 1, a sound card 2, a power amplifier 3, a dodecahedron speaker 4, a sound absorption coefficient measuring device 5, a six-microphone three-dimensional sound intensity probe 6, a display 7, a material or component to be measured 8, a total reflection plate 9 and an impermeable sound baffle 10.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Examples

As shown in fig. 1, the present embodiment provides a six-microphone three-dimensional sound intensity method sound absorption coefficient measurement system, including: the sound absorption measuring device comprises a PC (personal computer) 1, a sound card 2, a power amplifier 3, a regular dodecahedron loudspeaker 4, a sound absorption coefficient measuring device 5, a six-microphone three-dimensional sound intensity probe 6, a display 7, a material or component to be measured 8, a total reflection plate 9 and a sound-proof baffle 10;

the sound card 2 is inserted into the PC 1, the power amplifier 3 and the regular dodecahedron loudspeaker 4 are sequentially connected to form a sound production module which is mainly used for generating an omnidirectional sound wave signal, in order to enable the sound wave to be closer to a plane wave and ensure that an impermeable sound baffle can shield direct sound of the loudspeaker, the distance range between the loudspeaker and a material to be tested is 3-5m, and the optimal distance is 5 m;

in the present embodiment, the PC 1 is used to generate a single frequency noise signal; the sound card 2 is a high-frequency sound card with A/D conversion; the power amplifier 3 adopts a BSWA-PA300 power amplifier and has a frequency range of 20 Hz-20 kHz and a dynamic range of 102 dBA; the regular dodecahedron speaker 4 adopts BSWA-OS003A non-directional sound sources, and meets the requirements of ISO 140-3, ISO 140-4 and ISO 3382 standards on the non-directional sound sources.

In the embodiment, the sound absorption coefficient measuring device 5 adopts a sound absorption coefficient measuring platform based on Labview, and the sound absorption coefficient measuring platform based on Labview is connected with a six-microphone three-dimensional sound intensity probe 6 and a display 7 to form a sound receiving module;

the Labview-based sound absorption coefficient measuring platform comprises a PXI-Express case, a PXI embedded controller and a data acquisition card, wherein the PXI embedded controller and the data acquisition card are connected with the PXI-Express case through slots, the PXI embedded controller is provided with a Labview sound absorption coefficient measuring system, and the system comprises a data acquisition module, a six-microphone three-dimensional sound intensity measuring module, a sound absorption coefficient measuring module and a system error correction module. The data acquisition module is used for acquiring sound pressure data of each probe of the six microphones, the six-microphone three-dimensional sound intensity measurement module is used for completing time domain display and three-dimensional sound intensity calculation of each channel signal, the sound absorption coefficient measurement module is used for measuring a sound absorption coefficient, and the system error correction module is used for measuring an incident angle and an error value and correcting the incident angle and the error value.

The sounding module and the sound receiving module are respectively positioned at two sides of a material or a component to be measured 8, a sound-proof baffle plate 10 is arranged in the middle of the sounding module and is vertical to the material or the component to be measured and used for shielding direct sound from a loudspeaker, and the distance between the sound-proof baffle plate and the material or the component to be measured is determined according to the lowest frequency of measurement.

As shown in fig. 2, the six-microphone three-dimensional sound intensity probe is composed of six microphones, the relative positions of the six microphone probes are arranged in an opposite manner in pairs, a regular sphere is formed in space, a three-dimensional rectangular coordinate system is established with the geometric center of the regular sphere as an origin, the six microphones fall on X, Y, Z coordinate axes in pairs, the distance from each microphone to the origin is the same, and the distance is the circumscribed sphere radius R of the six microphone probe, as shown in table 1 below, the coordinates of the microphones 1 to 6 are (R, 0, 0), (-R, 0, 0), (0, R, 0), (0, -R, 0), (0, 0, R), (0, 0, -R).

Table 1 coordinate table of six microphones in rectangular space coordinate system

In the embodiment, the design values of the external sphere radius of the six-microphone three-dimensional sound intensity probe are 7mm, 12mm and 25mm, and the selection of the external sphere radius is determined according to the measurement frequency range.

In the embodiment, the six microphones of the six-microphone three-dimensional sound intensity probe adopt an MPA 2011/2-inch pre-polarized capacitor body free field microphone, the diameter of the MPA 2011/2-inch pre-polarized capacitor body free field microphone is 1/2 inches, the frequency response range can reach 20 Hz-20 kHz, the dynamic range is 16 dBA-134 dBA, and the background noise is less than 16 dBA.

In the embodiment, the PXI embedded controller is provided with Labview software, adopts a PCIe-8821 integrated controller, has functions of integrating a CPU, a hard disk drive, a RAM, an Ethernet, a video, a keyboard/mouse, a serial, a USB and other peripheral I/O, and can provide the system throughput of 8GB/s and the slot throughput of 2 GB/s;

in this embodiment, Adobe audio software is installed in the PC, the sound card is a high-frequency sound card with a/D conversion, and all speakers of the regular dodecahedron speaker are connected in series-parallel, so that the same-phase radiation of all speakers in the unit is ensured.

The PXI-Express case adopts an NI PXIe-1062Q case, can support 8 board cards at most, provides a diversified combination form for the number and the mode of input and output ports for signal acquisition, each slot can provide a special bandwidth up to 1GB/s, ensures the real-time acquisition and transmission of signals, and the total system bandwidth exceeds 3 GB/s; the running noise within the temperature range of 0 ℃ to 30 ℃ can be controlled within 43.6dBA, so that the low-noise running is ensured;

the data acquisition card adopts NI PXI-4461 and NI PXI-4462 sound and vibration modules, and the NI PXI-4461 module provides double-channel dynamic signal generation and double-channel dynamic signal acquisition, so that 2-path synchronous updating analog input and 2-path synchronous updating analog output can be realized; the NI PXI-4462 module provides four-channel dynamic signal acquisition and can realize 4-channel synchronous updating analog input. The highest sampling rates of the two data acquisition cards can reach 204.8kS/s, and both have 118dB dynamic ranges; the measurement of the embodiment adopts a 6-channel line array, adopts NI PXI-4461 and NI PXI-4462, and realizes the simultaneous acquisition of six-channel data.

In the embodiment, the diameter of the microphone adopted by the six-microphone three-dimensional sound intensity probe is 1/8-1/2 inches; the material or member to be measured 8 was a polyester fiber sound-absorbing board having dimensions (width × height × thickness) of 1.21 × 9 mm. The total reflection plate 9 and the sound-proof baffle plate 10 are both concrete plates, and the dimensions (width × height × thickness) are 1.5 × 1.0 × 2 cm.

The embodiment also provides a measuring method of the six-microphone three-dimensional sound intensity method sound absorption measuring system, which is carried out in a full anechoic chamber and comprises the following steps:

s1: determining the external sphere radius of the six-microphone three-dimensional sound intensity probe according to the measurement frequency range of the sound absorption coefficient of the material to be measured;

when the external sphere radius is 7mm, the effective measurement frequency range of the sound absorption coefficient measurement system is 1k-4 kHz; when the external sphere radius is 12mm, the effective measurement frequency range of the sound absorption coefficient measurement system is 500-2 kHz; when the external sphere radius is 25mm, the effective measurement frequency range of the sound absorption coefficient measurement system is 250-1 kHz;

determining the distance between the sound-proof baffle and the material or component to be measured according to the lowest frequency of the required measuring frequency range so as to reduce the diffraction of low-frequency sound;

when the distance between the sound-proof baffle and the material or the component to be measured is 0.5m, the lowest frequency is suitable for measuring 1 kHz; when the distance between the sound-proof baffle and the material or the component to be measured is 1m, the lowest frequency suitable for measurement is 500 Hz; when the distance between the sound-impermeable baffle and the material or member to be measured is 1.5m, it is suitable to measure the lowest frequency at 250 Hz.

S2: determining a measurement incidence angle, after determining a certain oblique incidence angle of a sound source, placing a material or a component to be measured according to the actual installation condition, adjusting the linear distance between the regular dodecahedron loudspeaker and the material or the component to be measured to be 5m, arranging a six-microphone three-dimensional sound intensity probe with the adjusted external sphere radius on a main reflected sound ray, taking the geometric central position of the six-microphone three-dimensional sound intensity probe as an original point, taking No. 1 and No. 2 microphones as X axes, and enabling the six-microphone three-dimensional sound intensity probe to be parallel to the material or the component to be measured; the No. 3 and No. 4 microphones are taken as Y axes and are vertical to the material or the component to be measured; the No. 5 and No. 6 microphones are taken as Z axes and are vertical to the horizontal plane; meanwhile, the center of the regular dodecahedron loudspeaker and the geometric center of the six-microphone probe are kept in the same horizontal plane, and after the distance between the sound-proof baffle and the material or the component to be measured is determined, the sound-proof baffle is placed perpendicularly to the material or the component to be measured;

in this embodiment, the optional measurement incidence angle is 45 °, and the sound-impermeable baffle is placed perpendicular to the material or component to be measured by a distance of 1 m.

S3: carrying out first measurement, measuring the sound intensity at the geometric center position of a six-microphone three-dimensional sound intensity probe under the condition of arranging a measured material or a measured component, sequentially sending noise signals of measured frequency by a regular dodecahedron loudspeaker, and receiving six-channel sound pressure signals by the six-microphone three-dimensional sound intensity probe:

the sound pressure at the geometric center position of the six-microphone three-dimensional sound intensity probe can be approximately estimated by averaging the sound pressures of the microphones, and the sound pressure is estimated in timeDomain P₀(t) and in the frequency domain P₀(f) Respectively as follows:

wherein, P_i(t) (i ═ 1-6) represents an expression of sound pressure of microphone No. 1-6 in the time domain; p_i(f) (i-1-6) represents an expression of sound pressure of the microphone No. 1-6 in the frequency domain.

Expression U of particle vibration velocity of each microphone at geometric center position of six-microphone probe in frequency domain_i(f) (i ═ 1-6) is:

U_i(f)＝[P₀(f)-P_i(f)]/j2πfρR (3)

according to the space geometric relation of the six-microphone probe, the U can be obtained_i(f) (i is 1-6) and component U of particle vibration speed in X, Y, Z three directions at geometric center position of six-microphone three-dimensional sound intensity probe_x、U_y、U_zThe relationship of (1):

the U can be obtained by combining (2), (3) and (4)_x、U_y、U_zSound pressure P to each microphone_i(i ═ 1 to 6):

wherein j is an imaginary unit, f is frequency, rho is air density, and R represents the external sphere radius of the six-microphone three-dimensional sound intensity probe.

The sound pressure signal received by the six-microphone three-dimensional sound intensity probe is transmitted to the embedded controller through the data acquisition cardAnd completing time domain display and three-dimensional sound intensity calculation of signals of each channel in a sound absorption coefficient measuring platform of Labview. Respectively carrying out cross-spectrum calculation on sound pressure signals received by the No. 1 and No. 2 microphones, the No. 3 and No. 4 microphones and the No. 5 and No. 6 microphones, and further calculating to obtain X, Y, Z three-direction sound intensity component I_1X(ω)、I_1Y(ω)、I_1Z(ω)：

Wherein G is_ABAnd the single-side cross-power spectral function of the sound pressure of the A microphone and the sound pressure of the B microphone is represented, and Im represents an imaginary part.

At this time, the measured reflected sound intensity I is the reflected sound intensity I of the material or component to be measured_r：

S4: other experimental settings are kept consistent, and an opaque baffle plate or a total reflection plate with the same size is placed at the same position of the material or the component to be measured, and a second measurement is carried out (no material or component to be measured exists).

Placing an opaque baffle or a total reflection plate with the same size and size at the same position as a material or a component to be detected, so that the three-dimensional sound intensity measured by the six-microphone three-dimensional sound intensity probe is close to the incident sound intensity, and the opaque baffle mainly plays a role in shielding direct sound from a loudspeaker to the six-microphone three-dimensional sound intensity probe;

noise signals with the same frequency are sequentially sent out by the regular dodecahedron loudspeaker, sound pressure signals received by the six-microphone three-dimensional sound intensity probe are transmitted to the embedded controller through the data acquisition card, and time domain display and three-dimensional sound intensity calculation of signals of all channels are completed in the sound absorption coefficient measurement platform based on Labview. Respectively performing cross spectrum meter on sound pressure signals received by No. 1 and No. 2 microphones, sound pressure signals received by No. 3 and No. 4 microphones and sound pressure signals received by No. 5 and No. 6 microphonesCalculating to obtain X, Y, Z three-direction sound intensity component I_2X(ω)、I_2Y(ω)、I_2Z(ω)：

At this time, the measured sound intensity can be regarded as the incident sound intensity I_i：

S5: and calculating the sound absorption coefficient and the incident angle. Transmitting the incident sound intensity and the reflected sound intensity obtained by the calculation in the steps S3 and S4 to a sound absorption measuring module, and calculating a sound intensity reflection coefficient R by using the measured incident sound intensity and reflected sound intensity at the geometric center position of the six-microphone probe and the vector information thereof as shown in fig. 3_I(theta), then obtaining the sound absorption coefficient of the material according to the relation between the sound absorption coefficient alpha (theta) and the sound intensity reflection coefficient, wherein the concrete calculation formula is as follows:

α(θ)＝1-R_I(θ) (11)

the angle of incidence θ may be averaged from the arctangent of the ratio of the X, Y axis components of the first and second measurements of three-dimensional sound intensity:

as shown in fig. 4, the difference between the incident angle θ and the incident angle θ' between the sound source and the perpendicular center line of the material measured by the protractor is taken as an absolute value, so as to obtain an incident angle measurement error value:

E_angle＝|θ′-θ| (13)

the method has low requirement on the measured material, can carry out measurement according to the actual installation condition of the material, realizes the measurement of the sound absorption coefficient of the building material under the oblique incidence condition, simultaneously obtains the incidence angle of the sound source by utilizing the vector characteristic measurement of the three-dimensional sound intensity, is beneficial to determining the direction of a main noise source in the actual engineering measurement, and can be applied to the actual condition that the incidence angle from some sound source to the material or structure is difficult to obtain.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.