An apparatus and method for measuring sound velocity using schlieren imaging.

Abstract

This invention discloses an apparatus and method for measuring sound velocity using schlieren imaging. A reflector, a sound field meter, a light shield, and an imaging component are arranged sequentially along a guide rail. The reflector is mounted on the guide rail via a first three-dimensional adjustment frame and a first four-wheel slide, sliding linearly. The sound field meter is mounted on the guide rail via a second four-wheel slide, sliding linearly. The light shield is mounted on the guide rail via a second three-dimensional adjustment frame and a third four-wheel slide, sliding linearly. The imaging component is mounted on a third three-dimensional adjustment frame and a fourth four-wheel slide, with the fourth four-wheel slide sliding linearly on the guide rail. This invention transforms sound velocity measurement using standing wave schlieren imaging. Standing wave schlieren images are captured using a mobile phone and camera. Schlieren imaging software is then used to accurately record the pixel values ​​corresponding to the ultrasonic probe diameter and the pixel differences between adjacent antinodes of the standing wave. Using the actual ultrasonic probe diameter as a comparison, the sound velocity is calculated using relevant formulas, achieving accurate measurement.

Description

Technical Field

[0001] This invention relates to a device and method for measuring the speed of sound in air, and more particularly to a device and method for measuring the speed of sound using schlieren imaging. Background Technology

[0002] Measuring the speed of sound in air is a classic physics experiment with significant practical applications. There are many methods for measuring the speed of sound in physics experiments, primarily the phase difference method. Time difference method Law, Resonance Interferometry Methods such as spectral analysis are used. Accurate sound velocity measurement systems have always been valued in the field of physics experiments; therefore, increasing the number of sound velocity measurement methods is of great significance. Common laboratory sound velocity measurements can be achieved using two ultrasonic probes, a signal generator, and an oscilloscope. The technology is relatively simple, and the system is relatively straightforward, mainly relying on the study of mechanics and electricity. This invention provides a device and method for measuring sound velocity using schlieren imaging. It primarily calculates the sound velocity value by measuring the wavelength of the schlieren standing wave, involving knowledge of thermodynamics, optics, electricity, mechanics, and computer technology. Summary of the Invention

[0003] To address the problems existing in the background technology, the present invention provides a device and method for measuring sound velocity using schlieren imaging, which is an experimental instrument system for measuring sound velocity that integrates thermodynamics, optics, electricity, mechanics and computer technology.

[0004] The technical solution adopted in this invention is:

[0005] I. A device for measuring sound velocity using schlieren imaging:

[0006] The device includes a reflector, a sound field meter, a light shield, and an imaging component, which are arranged sequentially along the guide rail.

[0007] The reflector is mounted on a first three-dimensional adjustment frame, which is mounted on a first four-wheel slide. The first four-wheel slide is mounted on a guide rail and can slide freely along a straight line. The sound field meter is mounted on a second four-wheel slide, which is mounted on a guide rail and can slide freely along a straight line. The light shield is mounted on a second three-dimensional adjustment frame, which is mounted on a third four-wheel slide. The third four-wheel slide is mounted on a guide rail and can slide freely along a straight line. The shooting component is mounted on a third three-dimensional adjustment frame, which is mounted on a fourth four-wheel slide. The fourth four-wheel slide is mounted on a guide rail and can slide freely along a straight line.

[0008] The reflector includes a spherical mirror and a spherical mirror support frame. The spherical mirror support frame is fixedly installed on the first three-dimensional adjustment frame. The spherical mirror is rotatably installed on the side of the spherical mirror support frame near the sound field instrument and is arranged towards the sound field instrument.

[0009] The sound field instrument includes a sound field instrument bracket, a lead screw slide, a movable platform, a first ultrasonic probe T1, a second ultrasonic probe T2, and a heating element. The sound field instrument bracket is mounted on a second four-wheel slide, and the vertical lead screw slide is mounted inside the sound field instrument bracket. The movable platform can move up and down and is mounted on the vertical guide rail of the lead screw slide, and moves by being threaded onto the lead screw of the lead screw slide. The first ultrasonic probe T1 is mounted on the movable platform of the lead screw slide and can move up and down with the movable platform. The second ultrasonic probe T2 is fixed on the bottom of the lead screw slide and does not move. The heating element is fixedly arranged between the first ultrasonic probe T1 and the second ultrasonic probe T2.

[0010] The first ultrasonic probe T1 and the second ultrasonic probe T2 are arranged facing each other, and the first ultrasonic probe T1 and the second ultrasonic probe T2 are arranged parallel to each other.

[0011] The heating element is electrically connected to an adjustable thermostat. The control signal output by the adjustable thermostat drives the heating element to heat up, thereby heating the surrounding air.

[0012] The first ultrasonic probe T1 and the second ultrasonic probe T2 are both electrically connected to the ultrasonic power meter. The ultrasonic power meter drives the first ultrasonic probe T1 and the second ultrasonic probe T2 to emit ultrasonic signals for detection.

[0013] The lead screw slide is electrically connected to the programmable stepper. The programmable stepper outputs a sine wave signal to drive the motor inside the lead screw slide to rotate, which in turn drives the lead screw of the lead screw slide to rotate, thereby driving the movable platform installed on the vertical guide rail of the lead screw slide to move up and down, thereby driving the first ultrasonic probe T1 to move up and down.

[0014] The light shield includes a light-blocking plate, a light-blocking disc, and an LED light source. The annular light-blocking disc is mounted on a second three-dimensional adjustment frame. A circular opening is provided in the center of the light-blocking disc. A semi-circular light-blocking plate is provided in the lower half of the opening, and a semi-circular through hole is formed in the upper half of the opening. The LED light source is mounted on the light-blocking disc and is electrically connected to the LED power supply.

[0015] The light emitted by the LED light source on the light shield passes through the sound field instrument and shines on the spherical mirror of the reflector, and is reflected. By adjusting the position and direction of the spherical mirror, the reflected light passes through the sound field instrument again and shines on the light-blocking plate of the light shielding disc. Then, the height of the light-blocking plate is adjusted so that the light passes through the upper half of the opening of the light shielding disc and enters the camera of the shooting component to be received.

[0016] The position of the light-blocking device on the guide rail is adjusted by the third and fourth wheel slides so that the light beam is focused onto the light-blocking plate. The vertical position of the light-blocking device is adjusted by the second three-dimensional adjustment frame to change the light flux entering the camera, thereby enabling the camera to acquire a schlieren image.

[0017] The signal generated by the ultrasonic power meter is input to two parallel and directly opposite first ultrasonic probe T1 and second ultrasonic probe T2 in the sound field instrument. The first ultrasonic probe T1 and the second ultrasonic probe T2 emit ultrasonic waves to generate an interference sound field. The movable platform in the sound field instrument is driven to move up and down by a programmable stepper, which in turn drives the first ultrasonic probe T1 on the movable platform to move up and down, changing the distance between the two ultrasonic probes, thereby obtaining the standing wave sound field.

[0018] When the adjustable thermostat is turned on, the heating element placed between the two ultrasonic probes begins to heat up, thereby increasing the number of air particles entering the interference sound field, thus increasing the medium density and making the schlieren image clearer.

[0019] II. A method for measuring sound velocity using schlieren imaging, the specific process of which is as follows:

[0020] Step S1: Turn on the ultrasonic power meter, and the first ultrasonic probe T1 and the second ultrasonic probe T2 will start working.

[0021] Step S2: Turn on the adjustable thermostat, and the heating element will start heating;

[0022] Step S3: Turn on the programmable stepper and control the lead screw in the lead screw slide to rotate and drive the first ultrasonic probe T1 to move through the movable platform to a suitable position so that a clear standing wave sound field is formed between the first ultrasonic probe T1 and the second ultrasonic probe T2.

[0023] Step S4: Turn on the LED power. The light emitted by the LED light source shines through the sound field meter and shines on the spherical mirror of the reflector and is reflected. By adjusting the position and direction of the spherical mirror, the reflected light passes through the sound field meter again and shines on the light-blocking plate of the light-blocking disc. The light then enters the camera of the shooting component through the upper part of the opening of the light-blocking disc and is received.

[0024] Adjust the position and direction of the spherical mirror so that the light reflected by the spherical mirror hits the center of the light-blocking plate inside the light-blocking disc;

[0025] The position of the light shield on the guide rail is moved by the third and fourth wheel slides, so that the light spot shining on the light shield plate of the light shielding disc is focused to form the clearest focal point.

[0026] Step S5: Turn on the computer, the camera of the shooting component, and the mobile phone. Focus the camera lens until you see a clear image of the first ultrasonic probe T1 on the camera's display screen. You can open the camera APP software on your mobile phone to observe the image acquired by the camera of the shooting component simultaneously.

[0027] Step S6: Adjust the vertical height of the shielding disc using the second three-dimensional adjustment frame until a schlieren image appears on the display screen of the camera of the imaging component;

[0028] Step S7: Continuously adjust the start / stop, positive / negative, and size functions on the programmable stepper, thereby adjusting the up-and-down movement of the movable platform, which in turn drives the first ultrasonic probe T1 above to move up and down until a schlieren image appears on the display screen of the camera of the imaging component, that is, a clear schlieren standing wave image appears in the mobile phone. Based on the schlieren standing wave image, image analysis and processing are performed to obtain the sound wave velocity value in the air, that is, the speed of sound.

[0029] The schlieren standing wave image described above has clearer standing wave patterns compared to the schlieren image.

[0030] When forming a schlieren standing wave image, the distance between the first ultrasonic probe T1 and the second ultrasonic probe T2 is an integer multiple of half the wavelength.

[0031] Step S7 specifically includes:

[0032] Step S7.1: Tap the camera button on the camera app on your phone to capture a schlieren standing wave image, and then transfer the captured schlieren standing wave image from your phone to your computer via WeChat.

[0033] Step S7.2: Open the schlieren image processing software on the computer and import the captured schlieren standing wave image. Measure and record the pixel value corresponding to the diameter of the first ultrasonic probe T1 and the pixel difference between the two adjacent antinodes of the standing wave in the image using the schlieren image software. Substitute these two values ​​and the known actual diameter value of the first ultrasonic probe T1 into the relevant formula, and finally calculate the sound wave velocity value in the air.

[0034] The sound speed value v is obtained in step S7 using the following formula:

[0035] ,

[0036] in, The actual diameter of the first ultrasonic probe T1 can be measured using vernier calipers. The output frequency of the ultrasonic power meter can be read on the instrument's display screen. This represents the pixel value corresponding to the diameter of the first ultrasonic probe T1 in the image. This represents the pixel difference between the antinodes of two adjacent standing waves in a schlieren standing wave image.

[0037] This invention transforms the method of sound velocity measurement using standing wave schlieren imaging. It captures standing wave schlieren images using a mobile phone and camera, and then uses schlieren imaging software to accurately record the pixel values ​​corresponding to the diameter of the ultrasonic probe and the pixel differences between the two adjacent antinodes of the standing wave. Using the actual diameter of the ultrasonic probe as a comparison object, the sound velocity is calculated using relevant formulas, thus achieving accurate measurement.

[0038] The beneficial effects of this invention are:

[0039] This invention constructs a device for measuring sound velocity using schlieren imaging and improves measurement accuracy by using the standing wave method, achieving good results.

[0040] This invention transforms the standing wave sound field into a schlieren image for measuring sound velocity, providing a new method for sound velocity measurement. It also utilizes the standing wave method for measurement and analysis to accurately obtain the sound velocity measurement.

[0041] This invention utilizes a mobile app to control a camera for non-contact measurement of schlieren images, thus further improving image quality and reducing human measurement errors. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the experimental instrument system;

[0043] Figure 2 It is a component diagram of the experimental instrument system;

[0044] Figure 3 This is a diagram of the light-shielding component;

[0045] Figure 4 This is a schematic diagram of a schlieren image used to measure the speed of sound in an embodiment.

[0046] Figure 5 This is a schematic diagram of a schlieren standing wave image used in an embodiment to measure the speed of sound.

[0047] The figure shows: 1-Spherical mirror support frame; 2-Spherical mirror; 12-First three-dimensional adjustment frame; 13-First four-wheel slide; 3-Sound field instrument bracket; 4-First ultrasonic probe T1; 5-Screw slide; 6-Modible platform; 7-Heating core; 8-Second ultrasonic probe T2; 9-LED light source; 10-Light shield; 11-Camera; 14-Guide rail; 15-Ultrasonic power meter; 16-Second four-wheel slide; 17-Adjustable thermostat; 18-Programmable stepper; 19-LED power supply; 20-Second three-dimensional adjustment frame; 21-Third four-wheel slide; 22-Third three-dimensional adjustment frame; 23-Fourth four-wheel slide; 24-Mobile phone; 25-Computer and schlieren image processing software; 26-Opening; 27-Light shield; 28-Light shielding disc. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] like Figure 1 and Figure 2 As shown, the device includes a reflector, a sound field meter, a light shield 10, and a shooting component. The reflector, sound field meter, light shield 10, and shooting component are arranged sequentially along the direction of the guide rail 14. The reflector, sound field meter, light shield, and camera are all mounted on the guide rail 14 via a four-wheel slide and can slide freely.

[0050] The reflector is mounted on the first three-dimensional adjustment frame 12, which is mounted on the first four-wheel slide 13. The first four-wheel slide 13 is mounted on the guide rail 14 and can slide freely along a straight line. The spherical mirror 2 on the reflector can rotate freely. The sound field meter is mounted on the second four-wheel slide 16, which is mounted on the guide rail 14 and can slide freely along a straight line. The light shield 10 is mounted on the second three-dimensional adjustment frame 20, which is mounted on the third four-wheel slide 21. The third four-wheel slide 21 is mounted on the guide rail 14 and can slide freely along a straight line. The shooting component is mounted on the third three-dimensional adjustment frame 22, which is mounted on the fourth four-wheel slide 23. The fourth four-wheel slide 23 is mounted on the guide rail 14 and can slide freely along a straight line.

[0051] like Figure 2 As shown, the reflector includes a spherical mirror 2 and a spherical mirror support frame 1. The spherical mirror support frame 1 is fixedly installed on the first three-dimensional adjustment frame 12. The spherical mirror 2 is rotatably installed on the side of the spherical mirror support frame 1 near the sound field instrument and is arranged towards the sound field instrument.

[0052] Specifically, the spherical mirror 2 can rotate in any direction, the spherical mirror support 1 can move up, down, left, and right through the first three-dimensional adjustment frame 12, and can slide freely along the guide rail 14 through the first four-wheel slide table 13.

[0053] like Figure 2 As shown, the sound field instrument includes a sound field instrument bracket 3, a lead screw slide 5, a movable platform 6, a first ultrasonic probe T14, a second ultrasonic probe T28, and a heating element 7. The sound field instrument bracket 3 is mounted on the second four-wheel slide 16, the vertical lead screw slide 5 is mounted inside the sound field instrument bracket 3, the movable platform 6 can move up and down, is mounted on the vertical guide rail of the lead screw slide 5, and moves by being threaded onto the lead screw of the lead screw slide 5; the first ultrasonic probe T14 is mounted on the movable platform 6 of the lead screw slide 5 and can move up and down with the movable platform 6, the second ultrasonic probe T28 is fixed on the support frame at the bottom of the lead screw slide 5 and does not move, and the heating element 7 is fixedly arranged between the first ultrasonic probe T14 and the second ultrasonic probe T28, specifically closer to the lower second ultrasonic probe T28;

[0054] The first ultrasonic probe T14 and the second ultrasonic probe T28 are arranged facing each other, and the first ultrasonic probe T14 and the second ultrasonic probe T28 are arranged parallel to each other. Specifically, the first ultrasonic probe T14 is arranged downwards and the second ultrasonic probe T28 is arranged upwards.

[0055] like Figure 1 As shown, the heating element 7 is electrically connected to the adjustable thermostat 17. The control signal output by the adjustable thermostat 17 drives the heating element 7 to heat up and work, thereby heating the surrounding air. Specifically, the adjustable thermostat 17 outputs a signal source with adjustable power. The adjustable thermostat 17 is connected to the heating element 7 through a wire to provide working power to the heating element 7.

[0056] The first ultrasonic probe T14 and the second ultrasonic probe T28 are both electrically connected to the ultrasonic power meter 15. The ultrasonic power meter 15 drives the first ultrasonic probe T14 and the second ultrasonic probe T28 to emit ultrasonic signals for detection. The ultrasonic power meter 15 outputs a sine wave signal source with fixed power and frequency. The ultrasonic power meter 15 is connected to the first ultrasonic probe T14 and the second ultrasonic probe T28 through wires, providing working signals for the first ultrasonic probe T14 and the second ultrasonic probe T28.

[0057] The lead screw slide 5 is electrically connected to the programmable stepper 18. The programmable stepper 18 outputs a sinusoidal wave signal of a certain power and frequency to drive the motor inside the lead screw slide 5 to rotate, which in turn drives the lead screw of the lead screw slide 5 to rotate, thereby driving the movable platform 6 mounted on the vertical guide rail of the lead screw slide 5 to move up and down, and thus driving the first ultrasonic probe T14 to move up and down. Specifically, the programmable stepper 18 outputs a pulse signal source that can be started and stopped at any time, and whose positive and negative values ​​and magnitudes are adjustable. The programmable stepper 18 is connected to the motor inside the lead screw slide 5 through wires to provide the working signal for the lead screw slide 5.

[0058] like Figure 3As shown, the light shield 10 includes a light-blocking plate 27, a light-blocking disc 28, and an LED light source 9. The annular light-blocking disc 28 is mounted on the second three-dimensional adjustment frame 20. A circular opening 26 is provided in the center of the light-blocking disc 28. The lower half of the opening 26 is provided with a semi-circular light-blocking plate 27. The light-blocking plate 27 is installed in the lower half of the opening 26 of the light-blocking disc 28. The upper half of the opening 26 forms a semi-circular through hole. The LED light source 9 is mounted on the edge of the light-blocking disc 28 and is electrically connected to the LED power supply 19.

[0059] Specifically, the light-blocking disc 28 can be moved up and down by the second three-dimensional adjustment frame 20, thereby controlling the appropriate amount of light to enter the camera through the light-blocking plate 27; the light-blocking disc 28 is fixed to the second three-dimensional adjustment frame 20 and slides freely on the guide rail 14 through the third and fourth wheel slides 21, thereby finding the focal point of the light reflected from the spherical mirror.

[0060] LED power supply 19 is connected to LED light source 9 via wires, providing power to LED light source 9. The emitted light is reflected by a spherical mirror and illuminates the interference sound field inside the sound field instrument. LED power supply 19 outputs a DC signal source of a certain voltage to drive LED light source 9 to illuminate the sound field.

[0061] The shooting components include a camera 11 and a mobile phone 24, which are wirelessly connected via WIFI, and the camera 11 can be controlled non-contactly via the mobile phone 24.

[0062] The specific implementation also includes a computer and software, which includes a computer and schlieren image processing software. The software installed in the computer is software for measuring the pixel difference of an image; the schlieren image processing software installed in computer 25 is software used to measure the pixel values ​​of standing waves and ultrasonic probe images.

[0063] like Figure 2 As shown, the light emitted by the LED light source 9 on the light shield 10 passes through the sound field instrument and shines on the spherical mirror 2 of the reflector and is reflected. By adjusting the position and direction of the spherical mirror 2, the reflected light passes through the sound field instrument again and shines on the light-blocking plate 27 of the light shielding disc 28. Then, the height of the light-blocking plate 27 is adjusted so that the light passes through the upper half of the opening 26 of the light shielding disc 28 and enters the camera 11 of the shooting assembly to be received.

[0064] The position of the light shield 10 on the guide rail 14 is adjusted by the third and fourth slides 21 so that the light beam is focused onto the light shield 27, forming the convergence point of the spherical mirror 2. The up and down position of the light shield 10 is adjusted by the second three-dimensional adjustment frame 20 to change the light flux entering the camera 11, thereby enabling the camera 11 to acquire a schlieren image.

[0065] The signal generated by the ultrasonic power meter 15 is input to the two parallel and directly opposite first ultrasonic probe T14 and second ultrasonic probe T28 in the sound field instrument. The first ultrasonic probe T14 and the second ultrasonic probe T28 emit ultrasonic waves to generate an interference sound field. The movable platform 6 in the sound field instrument is driven to move up and down by the programmable stepper 18, which in turn drives the first ultrasonic probe T14 on the movable platform 6 to move up and down, changing the distance between the two ultrasonic probes, thereby obtaining a clear standing wave sound field.

[0066] Turn on the adjustable thermostat 17, and the heating core 7 placed between the two ultrasonic probes will start to heat up and heat the air, thereby increasing the number of particulate matter in the air entering the interference sound field, thus increasing the density of the medium and making the schlieren image clearer.

[0067] Particulate matter in the air usually refers to suspended dust.

[0068] The specific embodiment of the present invention for measuring the speed of sound is as follows:

[0069] Step S1: Turn on the ultrasonic power meter 15, and the first ultrasonic probe T14 and the second ultrasonic probe T28 will start working.

[0070] Step S2: Turn on the adjustable thermostat 17, and the heating element 7 will start heating;

[0071] Step S3: Turn on the programmable stepper 18, start and stop the motor in the lead screw slide 5, so that the first ultrasonic probe T14 is in the appropriate position.

[0072] Step S4: Turn on the LED power supply 19. The emitted light shines on the spherical mirror 2 and is reflected to the light shield. Adjust the position and direction of the spherical mirror 2 so that the reflected light shines on the middle of the light blocking plate 27 inside the light shielding disc 28. Move the light shield so that the illuminated light spot is clearest, that is, the focal point of the spherical mirror 2.

[0073] Step S5: Turn on the computer, camera, and mobile phone. Focus the camera lens until you see a clear image of the first ultrasonic probe T14. Open the camera app on your mobile phone and observe the image acquired by the camera simultaneously.

[0074] Step S6: Adjust the vertical position of the second three-dimensional adjustment bracket 20 of the fixed shielding disc 28 until a schlieren image appears on the camera screen, such as... Figure 4 As shown;

[0075] Step S7: Continuously adjust the start / stop, positive / negative, and magnitude functions on the programmable stepper 18 until a clear schlieren standing wave image appears in the mobile phone, such as... Figure 5 As shown;

[0076] Step S8: Tap the camera app button on your phone 24 to capture a schlieren standing wave image, and then transfer the captured schlieren standing wave image from your phone to your computer via WeChat.

[0077] Step S9: Open the schlieren image processing software on the computer and import the captured schlieren standing wave image. Measure and record the pixel value corresponding to the diameter of the first ultrasonic probe T14 and the pixel difference between the two adjacent antinodes of the standing wave in the image using the schlieren image software. Substitute these two values ​​and the known actual diameter value of the first ultrasonic probe T14 into the relevant formula, and finally calculate the sound wave velocity in the air.

[0078] The velocity of sound is obtained using the following formula:

[0079] ,,

[0080] in, The actual diameter of the first ultrasonic probe T1 can be measured using vernier calipers. This indicates the output frequency of the ultrasonic power meter, which can be read on the instrument's display screen; This represents the pixel value corresponding to the diameter of the first ultrasonic probe T1 in the image. This represents the pixel difference between two adjacent antinodes in a schlieren standing wave image.

[0081] The data processing procedure in this embodiment is as follows:

[0082] Let the pixel value corresponding to the diameter of the first ultrasonic probe T1 be... The pixel value corresponding to the distance between two adjacent dark stripes in a schlieren standing wave image is , Let their ratio be a wavelength. ,but:

[0083]

[0084] because , , Therefore, the formula for measuring the speed of sound is derived as follows:

[0085]

[0086] That is:

[0087]

[0088] The frequency used by the ultrasonic generator is known. , = 0.001 .

[0089] The diameter of the first ultrasonic probe T1 was measured with vernier calipers as shown in Table 1 below.

[0090] Table 1

[0091] diameter Its uncertainty is ,so =0.004cm, the diameter of the first ultrasonic probe T1 is D=5.820±0.004cm.

[0092] The coordinates of multiple fringes were measured, and the data obtained are shown in Table 2 below. and It is the result of measuring the clearest stripe arbitrarily selected from multiple schlieren images.

[0093] Table 2

[0094] Therefore, the experimental sound wave velocity value is:

[0095]

[0096] The room temperature during the experiment was The theoretical value of the speed of sound at this temperature is calculated according to the formula in the literature. Therefore, the sound velocity measurement error of this method is relatively small. This verifies the correctness of the experimental system. This invention obtains the standing wave wavelength using schlieren imaging, then samples the data using software, and finally calculates the sound wave velocity value, achieving accurate measurement.

Claims

1. A device for measuring sound velocity using schlieren imaging, characterized in that: It includes a reflector, a sound field meter, a light shield (10) and a shooting assembly, which are arranged sequentially along the direction of the guide rail (14) on the guide rail (14); The reflector is mounted on the first three-dimensional adjustment frame (12), which is mounted on the first four-wheel slide (13). The first four-wheel slide (13) is mounted on the guide rail (14) and can slide freely along a straight line. The sound field meter is mounted on the second four-wheel slide (16), which is mounted on the guide rail (14) and can slide freely along a straight line. The light shield (10) is mounted on the second three-dimensional adjustment frame (20), which is mounted on the third four-wheel slide (21). The third four-wheel slide (21) is mounted on the guide rail (14) and can slide freely along a straight line. The shooting component is mounted on the third three-dimensional adjustment frame (22), which is mounted on the fourth four-wheel slide (23). The fourth four-wheel slide (23) is mounted on the guide rail (14) and can slide freely along a straight line. The sound field instrument includes a sound field instrument bracket (3), a lead screw slide (5), a movable platform (6), a first ultrasonic probe T1 (4), a second ultrasonic probe T2 (8), and a heating core (7); the sound field instrument bracket (3) is mounted on a second four-wheel slide (16), the vertical lead screw slide (5) is mounted inside the sound field instrument bracket (3), the movable platform (6) can move up and down and is mounted on the vertical guide rail of the lead screw slide (5), and moves by being threaded onto the lead screw of the lead screw slide (5); the first ultrasonic probe T1 (4) is mounted on the movable platform (6) of the lead screw slide (5) and can move up and down with the movable platform (6), the second ultrasonic probe T2 (8) is fixed on the bottom of the lead screw slide (5) and the heating core (7) is fixedly arranged between the first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8); The first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8) are arranged facing each other, and the first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8) are arranged in parallel and facing each other. The signal generated by the ultrasonic power meter (15) is input to the two parallel and directly facing first ultrasonic probe T1 (4) and second ultrasonic probe T2 (8) in the sound field instrument. The first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8) emit ultrasonic waves to generate an interference sound field. The movable platform (6) in the sound field instrument is driven to move up and down by the programmable stepper (18), which in turn drives the first ultrasonic probe T1 (4) on the movable platform (6) to move up and down, changing the distance between the two ultrasonic probes of the first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8), thereby obtaining the standing wave sound field. The heating element (7) is electrically connected to the adjustable thermostat (17). The control signal output by the adjustable thermostat (17) drives the heating element (7) to heat up and work, thereby heating the surrounding air.

2. The device for measuring sound velocity using schlieren imaging according to claim 1, characterized in that: The reflector includes a spherical mirror (2) and a spherical mirror support frame (1). The spherical mirror support frame (1) is fixedly installed on the first three-dimensional adjustment frame (12). The spherical mirror (2) is rotatably installed on the side of the spherical mirror support frame (1) near the sound field instrument and is arranged towards the sound field instrument.

3. The device for measuring sound velocity using schlieren imaging according to claim 1, characterized in that: The first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8) are both electrically connected to the ultrasonic power meter (15). The ultrasonic power meter (15) drives the first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8) to emit ultrasonic signals for detection. The lead screw slide (5) is electrically connected to the programmable stepper (18). The programmable stepper (18) outputs a sine wave signal to drive the motor inside the lead screw slide (5) to rotate, and drives the lead screw of the lead screw slide (5) to rotate, thereby driving the movable platform (6) installed on the vertical guide rail of the lead screw slide (5) to move up and down, thereby driving the first ultrasonic probe T1 (4) to move up and down.

4. The device for measuring sound velocity using schlieren imaging according to claim 1, characterized in that: The light shield (10) includes a light-blocking plate (27), a light-blocking disc (28), and an LED light source (9); the annular light-blocking disc (28) is mounted on the second three-dimensional adjustment frame (20), and a circular opening (26) is provided in the center of the light-blocking disc (28). A semi-circular light-blocking plate (27) is provided in the lower half of the opening (26), and a semi-circular through hole is formed in the upper half of the opening (26). The LED light source (9) is mounted on the light-blocking disc (28) and electrically connected to the LED power supply (19).

5. The device for measuring sound velocity using schlieren imaging according to claim 1, characterized in that: The light emitted by the LED light source (9) on the light shield (10) passes through the sound field instrument and shines on the spherical mirror (2) of the reflector and is reflected. By adjusting the position and direction of the spherical mirror (2), the reflected light passes through the sound field instrument again and shines on the light blocking plate (27) of the light shielding disc (28). The height of the light blocking plate (27) is then adjusted so that the light passes through the upper part of the opening (26) of the light shielding disc (28) and enters the camera (11) of the shooting assembly to be received. The position of the light shield (10) on the guide rail (14) is adjusted by the third and fourth wheel slides (21) so that the light beam is focused on the light shield (27). The up and down position of the light shield (10) is adjusted by the second three-dimensional adjustment frame (20) to change the light flux entering the camera (11), so that the camera (11) can acquire a schlieren image.

6. A method for measuring sound velocity using schlieren imaging applied to the apparatus described in any one of claims 1-5, characterized in that: The specific process is as follows: Step S1: Turn on the ultrasonic power meter (15), and the first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8) will start working. Step S2: Turn on the adjustable thermostat (17), and the heating element (7) will start heating; Step S3: Turn on the programmable stepper (18), control the screw in the lead screw slide (5) to rotate and drive the first ultrasonic probe T1 (4) to move via the movable platform (6), so that a standing wave sound field is formed between the first ultrasonic probe T1 (4) and the second ultrasonic probe T2 (8). Step S4: Turn on the LED power (19). The light emitted by the LED light source (9) passes through the sound field instrument and shines on the spherical mirror (2) of the reflector and is reflected. By adjusting the position and direction of the spherical mirror (2), the reflected light passes through the sound field instrument again and shines on the light-blocking plate (27) of the light-blocking disc (28). The light then passes through the upper part of the opening (26) of the light-blocking disc (28) and enters the camera (11) of the shooting component to be received. Adjust the position and direction of the spherical mirror (2) so that the light reflected by the spherical mirror (2) shines on the light-blocking plate (27) inside the light-blocking disc (28); The position of the light shield on the guide rail (14) is moved by the third and fourth wheel slides (21) so that the light spot on the light-blocking plate (27) of the light-blocking disc (28) is focused to form the clearest focal point; Step S5: Turn on the camera (11) of the shooting component, focus the lens of the camera (11) until a clear image is seen on the display screen of the camera (11), and observe the image acquired by the camera (11) of the shooting component simultaneously. Step S6: Adjust the vertical position of the shielding disc (28) using the second three-dimensional adjustment frame (20) until a schlieren image appears on the display screen of the camera (11) of the shooting component; Step S7: Continuously adjust the programmable stepper (18), and then adjust the movable platform (6) to move up and down, thereby driving the first ultrasonic probe T1 (4) above to move up and down until a schlieren image appears on the display screen of the camera (11) of the imaging component. Based on the schlieren standing wave image, perform image analysis and processing to obtain the air velocity value.

7. The method for measuring sound velocity using schlieren imaging according to claim 6, characterized in that: Step S7 specifically includes: Step S7.1: Tap the camera APP software on the mobile phone (24) to capture a schlieren standing wave image and transfer the captured schlieren standing wave image from the mobile phone to the computer; Step S7.2: Open the schlieren image processing software in the computer and import the captured schlieren standing wave image. Measure and record the pixel value corresponding to the diameter of the first ultrasonic probe T1 (4) and the pixel difference between the two adjacent antinodes of the standing wave in the image using the schlieren image software. Substitute these two values ​​and the known actual diameter value of the first ultrasonic probe T1 (4) into the relevant formula, and finally calculate the sound wave velocity value in the air.

8. The method for measuring sound velocity using schlieren imaging according to claim 6, characterized in that: The sound wave velocity value v is obtained in step S7 using the following formula: ， in, The actual diameter of the first ultrasonic probe T1(4); This indicates the output frequency of the ultrasonic power meter (15); The pixel value corresponding to the diameter of the first ultrasonic probe T1(4) in the image; This represents the pixel difference between the antinodes of two adjacent standing waves in a schlieren standing wave image.

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