A large range of automatic sound level measuring device and method based on Rayleigh disc principle

Abstract

The application provides a large-range automatic sound level measuring device and method based on the Rayleigh disc principle, which comprises a base, a horizontal pipe, a vertical pipe, a reflecting disc, a laser emitter, a horizontal displacement component, a photoelectric sensor, a thermometer and a control system; the measuring steps comprise: (1) zero calibration; (2) selection of a suitable pipe length; (3) measurement of sound field intensity; the application improves the measuring principle on the basis of the Rayleigh disc sound intensity measuring device developed by the predecessors, greatly increases the range of sound intensity measurement, and makes the measurement frequency continuous; the application can convert the directly measured physical quantity into sound intensity; the application improves the closure of the device, makes it convenient to move and improves the applicability; the application improves the automation level and greatly improves the data acquisition speed.

Description

Technical Field

[0001] This invention relates to a sound intensity measuring device, and more particularly to a multi-media, large-range, automated reflective sound level measuring device based on the Rayleigh disk principle. Background Technology

[0002] The Rayleigh disk, as a device for providing standard sound intensity, has long been a focus of attention. Its simple structure and ease of use under appropriate experimental conditions have led to its widespread application, such as its common use as a standard for calibrating microphones (before 1950). Rayleigh demonstrated that, when immersed in a flowing medium, the torsional moment on a thin disk tends to make the disk perpendicular to the direction of the flow. Koenig (1891), assuming the flow is streamlined and steady, mathematically determined the torsional moment on the disk. He found that the torsional moment of an infinitely thin disk of radius *a*, when the normal to the disk surface forms an angle with the direction of the flow, should be given by the following expression:

[0003]

[0004] Where L is torque. Let V be the density of the medium, and V be the average velocity of a small element in the volume of the sound field medium. Let the radius be the disk radius. The angle between the disk's normal and the direction of the sound wave vector.

[0005] In 1935, Louis V. provided a corrected formula for finite inertial disks. In 1939, A.C. Merrington and C.W. Woodley verified the accuracy of Rayleigh disk measurements of sound intensity. In 1945, Scott R.A. used a method of tracking smoke to measure the amplitude of infinitesimal elements in a fluid medium, further verifying the accuracy of the Rayleigh disk device. In 2015, Ivo Leibacher et al. applied the Rayleigh disk principle to the motion of tiny disk-shaped objects in an ultrasonic field, which can be applied to medical detection of red blood cells in blood vessels. The principle of Rayleigh disks has wide applications in acoustic measurement, medicine, and other fields.

[0006] Currently, commonly used sound intensity measurement devices are mainly electronic sound level meters or calibrated microphones. Their disadvantages lie in the limitations of electronic circuitry, making them difficult to use in various scenarios and under harsh physical conditions, such as high temperatures and underwater environments. Existing sound intensity measurement devices utilizing Rayleigh disks suffer from drawbacks such as: high cost due to the use of thick-walled copper tubing, inconvenience in movement; limited measuring range due to the small range of plastic torsion of the metal wire; inconvenient manual operation, difficult data reading, and significant reading errors; and inability to measure the intensity of sound fields with continuously changing frequencies. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the present invention provides a large-range automated reflective sound level measuring device based on the Rayleigh disk principle, including a base, a horizontal tube, a vertical tube, a reflective disk, a laser emitter, a horizontal displacement component, a photoelectric sensor, a thermometer, and a control system.

[0008] The horizontal tube is a transparent tube, horizontally mounted on the base; one end of the horizontal tube is equipped with a tube cap, and the center of the tube cap is equipped with a laser through hole; the other end of the horizontal tube is open.

[0009] The vertical pipe is installed vertically above the horizontal pipe, and its lower end is connected to the horizontal pipe; the upper end of the vertical pipe is provided with an end cap.

[0010] The reflective disc is suspended inside the horizontal tube by a thin metal wire. The center of the reflective disc is located at the axis of the horizontal tube, and the reflective disc is always located at the center of the axis of the horizontal tube. One end of the thin metal wire passes through the side wall of the reflective disc and passes through the diameter of the disc. The other end of the thin metal wire is connected to the center of the end cap of the vertical tube.

[0011] The laser emitter is mounted on the base, located at one end of the horizontal tube cap, directly opposite the laser through hole of the cap;

[0012] The horizontal displacement component is mounted on the base and is arranged parallel to the horizontal tube;

[0013] The photoelectric sensor is mounted on the horizontal displacement assembly and can move horizontally on the horizontal displacement assembly; the photoelectric sensor faces the direction of the horizontal tube.

[0014] The thermometer and control system are respectively mounted on the base. The control system is connected to the laser emitter, horizontal displacement component, photoelectric sensor and thermometer for data signal transmission. The control system includes a processor and buttons.

[0015] Furthermore, both sides of the reflective disk are reflective surfaces.

[0016] Furthermore, the horizontal tube is a three-section nested organic glass tube, with the middle tube fixed on the base and the tubes at both ends nested with the middle tube, allowing for extension and retraction. The synchronous extension and retraction of the tubes at both ends ensures that the reflective disc is always located in the center of the horizontal tube.

[0017] Furthermore, the horizontal displacement component can be any linear displacement mechanism such as a linear module, linear guide rail, ball screw linear transmission mechanism, or conveyor belt.

[0018] The processor runs the following sound intensity calculation formula:

[0019]

[0020]

[0021] Where k is the twist coefficient of the metal wire. α is the speed of sound, α is the twist angle of the metal filament, and a is the radius of the reflective disk. It is the acute angle between the direction of the medium's velocity field and the normal to the disk.

[0022] Coordinates of the time stain; The coordinates of the light spot when no sound field is applied; for The coordinates of the light spot are obtained by balancing in the sound field and measured by a photoelectric sensor.

[0023] This invention also provides a sound level measurement method, which uses the above-mentioned large-range automated reflective sound level measurement device based on the Rayleigh disk principle. The device of this invention is placed in the environment to be measured, and the measurement steps are as follows:

[0024] (1) Zero calibration:

[0025] Turn on the laser emitter and photoelectric sensor. Move the photoelectric sensor to the center of the horizontal tube using the horizontal displacement component. Slowly rotate the end cap of the vertical tube until the photoelectric sensor displays the maximum reading. Zeroing is complete. Record the coordinates of the light spot at this point. ;

[0026] (2) Select an appropriate pipe length:

[0027] According to the formula:

[0028]

[0029] Select a suitable horizontal tube length; where l is the length of the horizontal tube (resonant cavity), and n is an integer multiple of half the wavelength. Let n be the wavelength of the sound wave to be measured; by substituting an arbitrary value of n into the wavelength of the sound field to be measured, we obtain l; adjust the length of the horizontal tube so that the tube length is the value of l.

[0030] (3) Measure the sound field intensity:

[0031] Align the instrument's horizontal tube opening with the sound field. After stabilization, activate the horizontal displacement component via the control system. This causes the photoelectric sensor to traverse the slide rail twice, recording the coordinates of the light spot when no sound field is applied. and Balancing the coordinates of light spots in the sound field The sound intensity is calculated using a method in the processor and displayed on the monitor.

[0032] Furthermore, the input sound field frequency is controlled below the cutoff frequency to form a pure plane wave in the horizontal tube. The formula for the cutoff frequency is:

[0033]

[0034] in The radius of the horizontal pipe.

[0035] The beneficial effects of this invention are:

[0036] Based on the Rayleigh disk sound intensity measurement device developed by predecessors, this invention improves the measurement principle, greatly increases the range of sound intensity measurement, and makes the measurement frequency continuous; this invention can convert directly measured physical quantities into sound intensity; this invention improves the device's sealing performance, making it easy to move and improving its applicability; this invention improves the level of automation and greatly increases the data acquisition speed. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention;

[0038] Figure 2 This is a top view of the device of the present invention;

[0039] 1. Base 2. Horizontal tube 3. Vertical tube 4. Reflective disk 5. Laser emitter 6. Horizontal displacement component 7. Photoelectric sensor 8. Thermometer 9. Control system 10. Hard sponge base 11. Tube cap 12. Laser through hole 13. End cap 14. Metal filament. Detailed Implementation

[0040] See Figure 1-2 As shown:

[0041] This invention provides a large-range automated reflective sound level measuring device based on the Rayleigh disk principle, comprising a base 1, a horizontal tube 2, a vertical tube 3, a reflective disk 4, a laser emitter 5, a horizontal displacement component 6, a photoelectric sensor 7, a thermometer 8, and a control system 9.

[0042] The horizontal tube 2 is a transparent tube, which is horizontally mounted on the base 1. The horizontal tube 2 and the base 1 are connected by a hard sponge base 10. One end of the horizontal tube 2 is provided with a tube cap 11, and the center of the tube cap 11 is provided with a laser through hole 12. The other end of the horizontal tube 2 is open.

[0043] The vertical pipe 3 is vertically installed above the horizontal pipe 2, and its lower end is connected to the horizontal pipe 2; the upper end of the vertical pipe 3 is provided with an end cap 13.

[0044] The reflective disc 4 is suspended inside the horizontal tube 2 by a metal wire 14. The center of the reflective disc 4 is located at the axis of the horizontal tube 2, and the reflective disc 4 is always located at the center of the axis of the horizontal tube 2. One end of the metal wire 14 passes through the diameter of the reflective disc 4, and the other end is connected to the center of the end cap 13 of the vertical tube 3.

[0045] The laser emitter 5 is mounted on the base 1, located at one end of the cap of the horizontal tube 2, directly opposite the laser through hole 12 of the cap 11;

[0046] The horizontal displacement component 6 is mounted on the base 1 and is arranged parallel to the horizontal tube 2;

[0047] The photoelectric sensor 7 is mounted on the horizontal displacement assembly 6 and can move horizontally on the horizontal displacement assembly 6; the photoelectric sensor 7 faces the direction of the horizontal tube 2;

[0048] The thermometer 8 and the control system 9 are respectively mounted on the base 1. The control system 9 is connected to the laser emitter 5, the horizontal displacement component 6, the photoelectric sensor 7, and the thermometer 8 for data signal transmission. The control system 9 includes a processor and buttons. The processor is connected to a display via wired or wireless connection to display information such as sound intensity.

[0049] Both sides of the reflective disk 4 are reflective surfaces.

[0050] The horizontal tube 2 is a three-section nested organic glass tube. The middle tube is fixed on the base, and the tubes at both ends can extend and retract. The synchronous extension and retraction of the tubes at both ends ensures that the reflective disc 4 is always located in the center of the horizontal tube 2.

[0051] The device of the present invention is placed in the environment to be tested, and the sound level measurement operation steps are as follows:

[0052] (1) Zero calibration:

[0053] Turn on the laser emitter 5 and the photoelectric sensor 7, and move the photoelectric sensor 7 to the center of the horizontal tube using the horizontal displacement component 6; slowly rotate the end cap 13 of the vertical tube 3 until the reading fed back to the display by the photoelectric sensor 7 is the maximum, and the zeroing is completed;

[0054] (2) Select an appropriate pipe length:

[0055] According to the formula:

[0056]

[0057] Select a suitable length for the horizontal tube 2; where l is the length of the horizontal tube (resonant cavity), and n is an integer multiple of half the wavelength. Let n be the wavelength of the sound wave to be measured; by substituting an arbitrary value of n into the wavelength of the sound field to be measured, we obtain l; adjust the length of the horizontal tube 2 so that the tube length is the value of l.

[0058] (3) Measure the sound field intensity:

[0059] Align the opening of the instrument's horizontal tube 2 with the sound field. After stabilizing for 1 minute, activate the horizontal displacement component 6 via the control system 9. This causes the photoelectric sensor 7 to traverse the slide rail twice, recording the coordinates of the light spot when no sound field is applied. and Balancing the coordinates of light spots in the sound field The sound intensity is calculated using a method in the processor and displayed on the monitor.

[0060] This invention utilizes the Rayleigh disk principle to design a sound level meter. The plane wave sound field, on a scale much smaller than the wavelength, can be considered a uniform flow field. In spherical coordinates, compressing the axis of the sphere to an infinitesimal length, the formula for calculating the Rayleigh disk torque (König's formula) can be obtained according to Kirchhoff's disk theory.

[0061]

[0062] Where M is the torsional torque of the reflective disk. Let V be the density of the medium, V be the fluid velocity, and a be the radius of the reflective disk. The acute angle between the direction of the medium's velocity field and the normal to the disk.

[0063] Plane waves can be generated in horizontal pipes, with a sound pressure level of:

[0064] Where P mn The sound pressure level is given by m,n, which represents the (m,n)th normal mode. Let (m, n) be the sound pressure amplitude of the normal mode. It is an m-th order Bessel function. The eigenvalue is characteristic function The initial phase, Let (m, n) be the wave vector corresponding to the nth eigenvalue under the rigid wall boundary condition of the m-th Bessel equation, r be the displacement variable along the radial direction of the pipe, and z be the axial displacement variable of the horizontal pipe. ω is the angular frequency, and t is time;

[0065]

[0066]

[0067] Where k is the composite wave vector of the radial and axial waves, m represents the m-th angular characteristic function, and n represents the n-th radial characteristic function. The sound pressure solutions corresponding to the zeroth angular characteristic function and the zeroth radial characteristic function are, because The secondary wave is a plane wave, so it is only necessary to control it so that it does not generate. The secondary wave can satisfy the applicable conditions of the Koenig formula; as can be seen from the form of equation (2), if the input sound field frequency is controlled below the cutoff frequency, a pure plane wave can be formed in the tube. The cutoff frequency formula is:

[0068]

[0069] in For the speed of sound, The radius of the horizontal pipe;

[0070] When a Rayleigh disc (reflective disc) is balanced in a sound field, the following applies:

[0071]

[0072] Where M is the torsional torque of the reflective disk, k is the torsion coefficient of the metal wire, and α is the torsion angle of the metal wire;

[0073] The expression for sound intensity is:

[0074]

[0075]

[0076] in Where is the density of the acoustic medium, and W is the root-mean-square velocity of the fluid.

[0077] By combining (1), (6), and (7), we can obtain the functional relationship between the torsion angle of the reflective disk and the sound intensity.

[0078]

[0079] in The speed of sound is determined by temperature and the type of medium; taking air as an example:

[0080]

[0081] Where T is the sound field temperature, which is measured by a thermometer;

[0082] To improve measurement sensitivity, one end of the pipe is sealed with a cap, forming a standing wave tube. The sound intensity at the antinode of the standing wave is four times the measured sound intensity. By adjusting the pipe length to approximately an odd multiple of half the wavelength of the measured frequency, the center of the pipe becomes the antinode.

[0083] By utilizing the above phenomenon, sound intensity is converted into wire torque, and then the torsion is converted into light spot displacement through an optical lever, thus realizing sound intensity measurement.

[0084]

[0085] in Coordinates of the time stain; The coordinates of the light spot when no sound field is applied; for The coordinates of the light spot are obtained by balancing in the sound field and measured by a photoelectric sensor.

[0086] The present invention was calibrated with a handheld sound level meter, and the instrument uncertainty was 0.491 dB.

Claims

1. A large range automated sound level measuring device based on the principle of the Rayleigh disc, characterized in that: Includes a base, horizontal tube, vertical tube, reflective disk, laser emitter, horizontal displacement assembly, photoelectric sensor, thermometer, and control system; The horizontal tube is a transparent tube, horizontally mounted on the base; one end of the horizontal tube is equipped with a tube cap, and the center of the tube cap is equipped with a laser through hole; the other end of the horizontal tube is open. The vertical pipe is installed vertically above the horizontal pipe, and its lower end is connected to the horizontal pipe; the upper end of the vertical pipe is provided with an end cap. The reflective disc is suspended inside the horizontal tube by a thin metal wire, with the center of the reflective disc located at the axis of the horizontal tube; one end of the thin metal wire passes through the side wall of the reflective disc and through the diameter of the disc, while the other end is connected to the center of the end cap of the vertical tube. The laser emitter is mounted on the base, located at one end of the horizontal tube cap, directly opposite the laser through hole of the cap; The horizontal displacement component is mounted on the base and is arranged parallel to the horizontal tube; The photoelectric sensor is mounted on the horizontal displacement assembly and can move horizontally on the horizontal displacement assembly; the photoelectric sensor faces the direction of the horizontal tube. The thermometer and control system are respectively mounted on the base. The control system is connected to the laser emitter, horizontal displacement component, photoelectric sensor, and thermometer for data signal transmission. The control system includes a processor and buttons, and the processor runs the following sound intensity calculation formula: Where k is the twist coefficient of the metal wire. α is the speed of sound, α is the twist angle of the metal filament, and a is the radius of the reflective disk. The acute angle between the direction of the medium's velocity field and the normal to the disk is given. Coordinates of the time stain; The coordinates of the light spot when no sound field is applied; for The coordinates of the light spot are obtained by balancing in the sound field and measured by a photoelectric sensor.

2. The large-range automated sound level measuring device based on the Rayleigh disk principle according to claim 1, characterized in that: Both sides of the reflective disc are reflective surfaces.

3. The large-range automated sound level measurement device based on the Rayleigh disk principle according to claim 1, characterized in that: The horizontal tube is a three-section nested organic glass tube, with the middle tube fixed on the base and the tubes at both ends nested with the middle tube, allowing it to extend and retract.

4. The large-range automated sound level measuring device based on the Rayleigh disk principle according to claim 1, characterized in that: The horizontal displacement component can be any one of the following: a linear module, a linear guide, a ball screw linear transmission mechanism, or a conveyor belt.

5. A method for measuring sound level, characterized in that: Using the large-range automated sound level measuring device based on the Rayleigh disk principle as described in any one of claims 1-4, the device is placed in the environment to be measured, and the measurement steps are as follows: (1) Zero calibration: Turn on the laser emitter and photoelectric sensor, and move the photoelectric sensor to the center of the horizontal tube using the horizontal displacement component; slowly rotate the end cap of the vertical tube until the photoelectric sensor feeds back the maximum reading on the display, then the zeroing is complete; (2) Select an appropriate pipe length: According to the formula: Select a suitable horizontal tube length; where l is the horizontal tube length and n is an integer multiple of half the wavelength. Let n be the wavelength of the sound wave to be measured; by substituting an arbitrary value of n into the wavelength of the sound field to be measured, we obtain l; adjust the length of the horizontal tube so that the tube length is the value of l. (3) Measure the sound field intensity: Align the instrument's horizontal tube opening with the sound field. After stabilization, activate the horizontal displacement component via the control system. This causes the photoelectric sensor to traverse the slide rail twice, recording the coordinates of the light spot when no sound field is applied. and Balancing the coordinates of light spots in the sound field The sound intensity is calculated using a method in the processor and displayed on the monitor.

6. The sound level measurement method according to claim 5, characterized in that: The input sound field frequency is controlled below the cutoff frequency to form a pure plane wave in the horizontal tube. The formula for the cutoff frequency is: in The radius of the horizontal pipe.

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