Laser characterization device for acoustic performance of material in low-frequency sound field

Abstract

The utility model relates to a laser characterization device for acoustic performance of a material in a low-frequency sound field, belongs to the field of material performance testing, and solves the problem that an existing acoustic performance measuring device cannot measure the vibration condition of small-size samples of centimeter and millimeter orders of magnitude in the low-frequency sound field. Comprising a sound wave emission assembly and a laser detection assembly. The sound wave emission assembly is used for emitting low-frequency-band sound waves, so that the sample array generates vibration under the action of a sound wave field; wherein the sample array is formed by orderly arranging samples consisting of materials with different material components or different structures; the laser detection assembly comprises a laser and a photoelectric detector; wherein the laser is used for emitting laser to the surface of a sample, and the photoelectric detector is used for receiving reflected laser on the surface of the sample and generating an electric signal representing a light spot displacement condition; the displacement of the light spot represents the vibration condition of the surface of the sample. The device has high spatial resolution capability and can be used for rapidly measuring the acoustic performance of centimeter-level and millimeter-level samples.

Description

Technical Field

[0001] The invention relates to the field of material performance testing, and in particular to a laser characterization device for acoustic performance of materials in a low-frequency sound field. Background Art

[0002] The acoustic properties of a material can be obtained by detecting its vibration in an acoustic field. With the development of "material genetic engineering", the use of high-throughput preparation methods and high-throughput characterization has effectively accelerated the research and development of materials. At present, 3D printing technology can be used to quickly obtain different acoustic materials, and at the same time, micro-cavity structures at the millimeter level can be introduced into the material to optimize its low-frequency sound absorption performance. Different components and different structures make the material variety very rich.

[0003] The existing methods for detecting the acoustic properties of materials are mainly reverberation method, standing wave tube method and on-site measurement method. Among them, the reverberation method calculates the sound absorption coefficient by measuring the reverberation time before and after the installation of the sound-absorbing material. The disadvantages are that it requires a large area of ​​the material to be tested, inconvenient installation, poor comparability (the measurement results of the same material in different reverberation chambers vary greatly), and the sound absorption coefficient is easily affected by the location of the material and the sound absorption area; the standing wave tube method calculates the sound absorption coefficient by measuring the ratio of the maximum sound pressure to the minimum sound pressure, that is, the standing wave ratio. The disadvantage is that in order to obtain a complete standing wave, the length of the standing wave tube needs to reach half the wavelength. Since the waveguide has a cut-off frequency limit, low-frequency band measurement requires the standing wave tube to have a larger diameter. The disadvantage is that For liquid medium measurement, the standing wave tube length and measurement frequency are limited. The standing wave tube length must be at least half a wavelength. The measurement frequency is not effective at the low frequency or high frequency limit. For low-frequency sound waves, a measurement tube of more than ten meters and a large diameter may be required. Therefore, it is costly and impractical and cannot achieve high-throughput characterization of small samples. The on-site measurement method is to calculate the sound absorption coefficient by measuring the reflected pulse on site through a sound pressure meter placed at a certain distance in front of the sample to be measured. The disadvantage is that in the low-frequency band, it is difficult to distinguish the emitted and returned low-frequency pulses in the time domain, and the distance between the sound pressure meter and the sample and the sample size restrict each other. In addition, in the low-frequency band measurement, the reflected sound more reflects the characteristics of spherical waves, so there is a near-field error in the sound intensity measurement, the diffusion of reflected sound energy causes the measured low-frequency sound absorption coefficient to be smaller than the actual low-frequency sound absorption coefficient, and the material size affects the measurement effect.

[0004] When detecting the vibration of materials with a size of centimeters or millimeters in a low-frequency acoustic field, the spatial resolution of the far-field imaging of the above-mentioned methods can only reach the order of meters, which is much larger than the size of a single small sample. Therefore, it is impossible to perform low-frequency acoustic performance tests on small samples, and it is even more impossible to quickly perform low-frequency acoustic performance tests on a sample sequence composed of multiple small samples. In short, the above-mentioned measurement methods cannot meet the needs of characterizing the low-frequency acoustic performance of materials. Utility Model Content

[0005] In view of the above analysis, the utility model aims to provide a laser characterization device for the acoustic properties of materials in a low-frequency sound field, so as to solve the problem that the existing devices are unable to quickly measure the acoustic properties of multiple small samples of different materials and sizes in the order of centimeters or millimeters in a low-frequency sound field.

[0006] The purpose of this utility model is mainly achieved through the following technical solutions:

[0007] A laser characterization device for acoustic properties of materials under low-frequency sound field, comprising: an acoustic wave emission component and a laser detection component; wherein:

[0008] The acoustic wave emitting component is used to emit low-frequency acoustic waves so that the sample array is in the acoustic wave field; wherein the sample array is formed by materials of different components or structures being orderly arranged on a substrate;

[0009] The laser detection component includes a laser and a photodetector; wherein the laser is used to emit laser light to the sample surface, and the photodetector is used to receive the reflected laser light from the sample surface and generate an electrical signal representing the displacement of the light spot, wherein the displacement of the light spot reflects the vibration of the sample surface.

[0010] Specifically, the sound wave transmitter includes: a low-frequency signal generator, a power amplifier and a speaker electrically connected in sequence; wherein the speaker is suspended obliquely above the sample array, or is placed obliquely above the sample array through a retractable support frame; the low-frequency signal generator is used to generate a low-frequency electrical signal, which is amplified by the power amplifier and transmitted to the speaker, and the speaker converts it into a low-frequency sound wave signal for transmission.

[0011] Furthermore, it also includes a medium acoustic measurement environment component; the medium extension component includes: a water tank, two glass columns extending from the outside of the water tank to the inside of the water tank, and sound-absorbing material; wherein the speaker is an underwater speaker; the speaker and the sample are placed inside the water tank filled with water; the bottom of the glass column is sealed, and the emission light path is focused on the sample surface from the outside of the water tank through one of the glass columns; the reflected laser on the sample surface is emitted through the other glass column to the photodetector located outside the water tank; the sound-absorbing material covers the inner surface of the water tank.

[0012] Furthermore, the device also includes two translation stages; wherein the sample array is loaded on the first translation stage, and the photodetector is placed on the second translation stage; the two translation stages are used to adjust the position and angle of the sample array and the photodetector, respectively.

[0013] Furthermore, the laser detection component also includes: a beam expander and a focusing mirror A in the emission light path, and a focusing mirror B in the reflection light path; wherein the emission laser is focused on the surface of the sample to be measured through the beam expander and the focusing mirror A, and the laser reflected by the sample surface is focused on the sensing surface of the photodetector through the focusing mirror B.

[0014] Specifically, the photoelectric detector adopts a two-quadrant detector, and the detector generates two photocurrent signals based on the light intensity of the laser received by two detection areas respectively; and the light spot displacement is obtained based on the two photocurrent signals.

[0015] Furthermore, the loudspeaker, the laser detection assembly, and the two translation stages are detachably packaged in a shell, and the shell is used to shield interference from ambient light.

[0016] Furthermore, the low-frequency signal generator and the power amplifier are placed in a metal shielding box.

[0017] Specifically, the samples to be tested in the sample array have similar thickness and area, and the area scale is from square millimeters to square centimeters, for example, 1±0.01 cm 2 The samples are spaced apart from each other at a scale ranging from millimeters to centimeters, for example, 0.5±0.05 cm, and are arranged in an orderly manner on a substrate to form a sample array.

[0018] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0019] 1. Using laser as a probe to scan the near-field acoustic information on the sample surface, breaking through the traditional diffraction limit and greatly improving the resolution, it can be used to detect the acoustic properties of samples with smaller sizes, especially the response to low-frequency sound wave signals;

[0020] 2. The translation control component can be used to quickly characterize a large number of samples to be tested, so the detection speed is fast;

[0021] 3. Equipped with a medium acoustic measurement component, the device can be applied to a variety of fluid medium environments to test the acoustic properties of materials in different media, so it has a wide range of applications;

[0022] 4. The optical path structure of the device is simple, and each component can be debugged independently, which can save preparation time before the experiment. Therefore, it is easy to use and practical.

[0023] 5. The laser detection component is encapsulated in a shell, and the signal generator and power amplifier are placed in a metal shielding box to shield interference from the external environment and provide stable conditions for testing, so the device has good stability.

[0024] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the following content, and some advantages can be obvious from the description or understood by implementing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents specifically pointed out in the text and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components.

[0026] Figure 1 Schematic diagram of a laser characterization device for acoustic properties of materials under low-frequency sound fields;

[0027] Figure 2 A schematic diagram of the structure of the media extension component.

[0028] Reference numerals

[0029] 1- low frequency signal generator; 2- power amplifier; 3- speaker; 4- first translation stage; 5- laser; 6- beam expander; 7- focusing mirror A; 8- second translation stage; 9- focusing mirror B; 11- photodetector; 12- metal shielding box; 13- shell; 14- sample; 15- water tank; 16- underwater speaker; 17- glass column; 18- sound absorbing material. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0031] The acoustic properties of materials are determined by the composition and structure of the materials. Materials with different acoustic properties have different application directions. Corresponding to the refractive index of materials that people generally care about in optics, the main parameter describing the acoustic properties of materials is usually the acoustic refractive index of the material, that is, considering the difference between the propagation of sound waves outside the material and inside the material. The measurement of the acoustic properties of materials needs to be realized through the interaction between materials and sound waves. The changes of the sample material to the sound field are analyzed by acoustic measurement. People have developed some methods to characterize the acoustic properties of materials, such as reverberation chamber method, standing wave tube method and field measurement method. The scale of the spatial resolution unit of the sound wave is proportional to the wavelength of the sound wave. Taking underwater low-frequency sound waves as an example, the wavelength of sound waves at the hundred-hertz level is about 3 meters, which greatly limits the spatial resolution of analyzing the performance of sample materials by acoustic measurement. Therefore, traditional measurement methods cannot meet the acoustic performance measurement of small-sized samples in the low-frequency band.

[0032] Based on the above ideas, the design principle of the laser characterization device for acoustic properties of materials under low-frequency sound field described in the utility model is: focus the laser on the sample surface in the low-frequency sound field, and use a photoelectric detector to receive the laser signal reflected by the sample surface; when the sample surface vibrates under the low-frequency sound field, that is, when the surface is displaced, the reflected laser spot focused on the detector also displaces accordingly; the detector generates a corresponding electrical signal based on the movement of the spot; based on the electrical signal, the amplitude and phase information are obtained by using a signal processing method to obtain the vibration condition of the material under the low-frequency sound field.

[0033] A specific embodiment of the utility model discloses a laser characterization device for acoustic properties of materials under low-frequency sound fields, such as Figure 1 As shown, it mainly includes: an acoustic wave emitting component and a laser detection component; wherein the acoustic wave emitting component is used to emit low-frequency acoustic waves, so that the sample array vibrates under the action of the acoustic wave field; wherein the sample array is formed by materials of different components or different structures being arranged in an orderly manner on a substrate; the laser detection component includes a laser and a photodetector; wherein the laser is used to emit laser to the sample surface, and the photodetector is used to receive the reflected laser from the sample surface to generate an electrical signal representing the displacement of the light spot; the displacement of the light spot represents the vibration of the sample surface.

[0034] For example, when preparing a sample array on a substrate, the thickness of small samples of different materials is similar, and the sample area can be about 1 cm 2 ; The distance between each sample in the sample array can be about 5 mm.

[0035] Specifically, the sound wave control component is used to generate sound waves with frequencies of hundreds to kilohertz, that is, low-frequency sound wave signals, including: a low-frequency signal generator, a power amplifier, and a speaker; further, a metal box can be used to encapsulate the signal generator and the power amplifier to shield environmental interference.

[0036] During implementation, the low-frequency signal generator generates a preset low-frequency electrical signal, which is amplified by the power amplifier and transmitted to the speaker, causing the speaker to emit low-frequency sound waves. The speaker is placed at a certain distance above the sample array, which can be achieved by hanging or using a supporting tool.

[0037] Exemplarily, the low-frequency signal generator is adjusted to output a signal in the form of a sine wave; the speaker is adjusted so that its straight-line distance from the sample array is about 30 cm, and the angle between the sound wave and the normal direction of the sample surface is 30°, so that the sample array is in the low-frequency sound field established by the speaker.

[0038] Furthermore, the device also includes a media extension component, such as Figure 2 As shown, it is used to provide other media testing environment for the device.

[0039] Take the underwater test environment as an example. Figure 2 As shown, the extended medium component includes: a water tank, two glass columns extending from the outside of the water tank to the inside of the water tank, and sound-absorbing material; wherein the speaker is an underwater speaker, which is placed in the water tank filled with water together with the sample; the glass column is sealed at one end close to the sample surface to isolate the water outside the glass tube, providing a propagation environment of the same medium as that outside the water tank for the optical path, avoiding the influence of the water surface fluctuation caused by the sound waves in the water, and ensuring the stability of the laser optical path, and the emission optical path is focused on the sample surface from the outside of the water tank through one of the glass columns; the reflected laser on the sample surface is emitted to the photoelectric detector outside the water tank through the other glass column; the sound-absorbing material covers the inner surface of the water tank to absorb the reflection of the sound waves by the water tank wall.

[0040] Preferably, the sound absorbing material can be selected from rubber and polyurethane materials.

[0041] Furthermore, the laser detection component also includes: a beam expander and a focusing mirror A in the emission light path, and a focusing mirror B in the reflection light path; wherein the emission laser is focused on the surface of the sample to be measured through the beam expander and the focusing mirror A, and the laser reflected by the sample surface is focused on the sensing surface of the photodetector through the focusing mirror B; the positions and angles of the beam expander, the focusing mirror A and the focusing mirror B are adjustable.

[0042] Specifically, the photoelectric detector uses a two-quadrant detector, which generates two photocurrent signals based on the light intensity of the laser received in the two detection areas; the light spot displacement is obtained based on the two photocurrent signals. The two-quadrant detector has the advantages of fast response speed and high sensitivity, and can provide real-time feedback on the vibration information of the sample surface under low-frequency sound fields.

[0043] Furthermore, a filter is added between the focusing lens B of the laser reflection light path and the two-quadrant detector to filter light waves with frequencies different from the laser; a black rubber tube is installed on the two-quadrant detector to shield ambient light.

[0044] Preferably, during implementation, the positions and angles of the laser head, beam expander, focusing lens A, and sample array in the incident light path are adjusted so that the angle between the incident light beam and the sample surface is 45°. ° , and then adjust the focusing mirror in the reflected light path at a symmetrical angle to focus the laser beam on one focus, adjust the position and angle of the two-quadrant detector so that the reflected laser focus is located at the detector sensing surface, and the reflected laser beam is perpendicular to the plane where the detector is located. The laser emits laser light, and the emitted laser light is focused on the sample surface through the beam expander and focusing mirror A; the scattered light of the sample is collected through the focusing mirror B, so that the laser reflected from the sample surface is focused on the two-quadrant detector; the two-quadrant detector generates two photocurrent signals based on the light intensity of the laser received by each of the two detection areas.

[0045] Furthermore, the above device also includes two translation stages, which are used to load the sample array and the two-quadrant detector respectively to adjust the position and angle of the sample array and the two-quadrant detector.

[0046] During implementation, the laser detection assembly is kept stationary, the first translation stage is manipulated to irradiate the laser on different samples or different positions of the samples, and the second translation stage is manipulated to make the focus of the reflected laser be located at the detector sensing surface.

[0047] Preferably, the speaker, laser detection assembly, and two translation stages are detachably packaged in a shell, and the shell is used to shield interference from ambient light and provide a stable environment for detection to obtain accurate test results.

[0048] In general, the high-throughput characterization device for the low-frequency sound absorption and shock absorption performance of the above-mentioned material firstly uses laser as a near-field "probe" in low-frequency acoustic measurement to directly measure the vibration information of the sample, thereby breaking through the low-frequency diffraction limit of acoustic measurement. Compared with the existing technologies such as the reverberation chamber method that requires large material size and the standing wave tube method with limited tube length, the device described in the present invention has a wide range of applications, low cost, and strong practicality; secondly, the effective combination of the acoustic wave control component, the laser detection component, and the translation stage makes the low-frequency acoustic measurement of the sample efficient and portable; in addition, the design route of the device is clear, and each component part can be debugged independently, which can save preparation time before testing; by adding a shell and a metal shielding box, the device has a stable environment and conditions when performing detection, so the device has good stability and accurate measurement results; finally, by setting a medium extension component, the device is suitable for measuring the amplitude of the material surface in a low-frequency sound field in a variety of media, and has a wide range of applications.

[0049] The present invention does not involve any software improvements. The present invention only requires that each device with corresponding functions be connected through the connection relationship given in the embodiment of the present invention, and does not involve any program software improvements. As for the connection method between the hardware devices with corresponding functions, it can be implemented by those skilled in the art using existing technologies, and will not be described in detail here.

[0050] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention.

Claims

1. A laser characterization device for acoustic properties of materials under low-frequency sound field, characterized in that: include: Acoustic wave emission component and laser detection component; wherein, The acoustic wave emitting component is used to emit low-frequency acoustic waves, so that the sample array vibrates under the action of the acoustic wave field; wherein the sample array is composed of a plurality of small sample arrays composed of different materials and different structures arranged on a substrate; The laser detection component includes a laser and a photodetector; wherein the laser is used to emit laser light to the sample surface, and the photodetector is used to receive the reflected laser light from the sample surface and generate an electrical signal representing the displacement of the light spot, wherein the change in the displacement of the light spot reflects the vibration of the sample surface.

2. The laser characterization device for acoustic properties of materials under low-frequency sound field according to claim 1, characterized in that: The sound wave transmitter comprises: a low-frequency signal generator, a power amplifier and a speaker which are electrically connected in sequence; wherein the speaker is suspended obliquely above the sample array, or is placed obliquely above the sample array through a retractable support frame; the low-frequency signal generator is used to generate a low-frequency electrical signal, which is amplified by the power amplifier and transmitted to the speaker, and the speaker converts the signal into a low-frequency sound wave signal for transmission.

3. The laser characterization device for acoustic properties of materials under low-frequency sound field according to claim 2, characterized in that: It also includes a medium extension component; the medium extension component includes: a water tank, two glass columns extending from the outside of the water tank to the inside of the water tank, and sound-absorbing material; wherein the speaker is an underwater speaker; the speaker and the sample are placed inside the water tank filled with water; the emission light path is focused on the sample surface from the outside of the water tank through one of the glass columns; the reflected laser on the sample surface is emitted through the other glass column to the photodetector located outside the water tank; the sound-absorbing material covers the inner surface of the water tank.

4. The laser characterization device for acoustic properties of materials under low-frequency sound field according to claim 2, characterized in that: It also includes two translation stages; wherein the sample array is loaded on the first translation stage, and the photoelectric detector is placed on the second translation stage; the two translation stages are used to adjust the position and angle of the sample array and the photoelectric detector respectively.

5. The laser characterization device for acoustic properties of materials under low-frequency sound field according to claim 4, characterized in that: The laser detection assembly also includes: a beam expander and a focusing mirror A in the emission light path, and a focusing mirror B in the reflection light path; wherein the emission laser is focused on the surface of the sample to be measured through the beam expander and the focusing mirror A, and the laser reflected by the sample surface is focused on the sensing surface of the photoelectric detector through the focusing mirror B.

6. The laser characterization device for acoustic properties of materials under low-frequency sound field according to claim 5, characterized in that: The photoelectric detector adopts a two-quadrant detector, and the detector generates two photocurrent signals based on the light intensity of the laser received by two detection areas respectively; based on the amplification and difference of the two photocurrent signals, an electrical signal representing the displacement of the light spot is obtained.

7. The laser characterization device for acoustic properties of materials under low-frequency sound field according to claim 6, characterized in that: The loudspeaker, the laser detection assembly and the two translation stages are detachably packaged in a shell, and the shell is used to shield the interference of ambient light.

8. The laser characterization device for acoustic properties of materials under low-frequency sound field according to claim 4, characterized in that: The low-frequency signal generator and the power amplifier are placed in a metal shielding box.

9. The laser characterization device for acoustic properties of materials in a low-frequency sound field according to any one of claims 1 to 8, characterized in that: The samples to be tested in the sample array have similar thickness and area, with an area scale of square millimeters to square centimeters; the intervals between the samples range from millimeters to centimeters, and the samples are arranged in order on the substrate to form a sample array.

Images