Visual quasi-plane ultrasonic standing wave demonstration instrument

Abstract

A visible quasi-plane ultrasonic standing wave demonstration instrument comprises an ultrasonic power signal generator, an ultrasonic transmitting head, a sound reflecting surface flat plate, a liquid nitrogen fog making cup, a lifting screw rod and windproof glass. The ultrasonic power signal generator drives the ultrasonic emission head to generate a quasi-plane ultrasonic incident wave, the ultrasonic incident wave is reflected back at the sound reflection surface flat plate, the reflected wave and the incident wave are coherently superposed to form a standing wave, and cold nitrogen in the liquid nitrogen fog making cup enters the sound field space to form a cold nitrogen and air mixed medium. When the lifting screw rod adjusts the distance between the emitting surface and the reflecting surface to be integral multiples of the half-wavelength of the mixed medium sound wave, the cold liquid nitrogen mist can clearly present stable quasi-plane standing waves, the visualization of the standing waves can describe the three-dimensional characteristics of spatial standing wave distribution and antinode nodes, the interest of people can be easily attracted, and the application prospect is wide. And standing wave concepts, images and characteristics can be intuitively known, which is of great significance to college physics classroom teaching.

Description

Technical Field

[0001] The utility model relates to the field of physical experiment teaching, in particular to an acoustic demonstration instrument, in particular to a visible quasi-planar ultrasonic standing wave demonstration instrument. Background Art

[0002] When two harmonic waves with the same vibration direction, equal amplitude, same frequency and constant phase difference propagate in opposite directions on the same straight line, they are superimposed to form a standing wave. It is usually obtained by a wave reflecting back from an interface and superimposing itself. When the distance between the transmitting end and the reflecting end is an integer multiple of half a wavelength, a stable standing wave is obtained. Each point in the standing wave formation area performs simple harmonic motion with the same frequency and different amplitudes. The position with the largest amplitude is called the antinode, and the position with zero amplitude is called the node.

[0003] Standing waves are one of the important contents in university physics teaching. Sound propagates in the air as mechanical longitudinal waves. Sound waves with a frequency exceeding 20kHz are called ultrasonic waves. They have good directional propagation characteristics, but they do not cause people's hearing. Therefore, the ultrasonic standing waves generated by ultrasonic waves in the air cannot be seen or heard, and it is difficult for students to understand and experience the characteristics of ultrasonic standing waves. In order to assist students in learning the phenomenon of sound standing waves during the teaching process, people have invented a variety of standing wave demonstrators, the most common of which are: Quint tube (1866), which uses kerosene, light wood chips, polyester foam particles, etc. as auxiliary media in the tube; Rubens flame tube (1905), which uses gas flame as auxiliary medium; ultrasonic atomization standing wave demonstrator (2018), which uses water mist after ultrasonic atomization as medium; these devices can well demonstrate the distribution of nodes and antinodes of standing waves and the amplitude of each point, but only the standing wave image in the horizontal direction can be observed. The distance between the transmitting end and the reflecting end is fixed, and the standing wave is obtained by adjusting the frequency. Ultrasonic levitation (1975, 1986), using lightweight paper sheets, particles, etc. as media, can demonstrate the distribution of nodes and antinodes of standing waves, but the stereoscopic image of the standing waves and the details of the sound pressure distribution cannot be observed. Utility Model Content

[0004] In view of the problems that the existing technology cannot present the stereoscopic image of ultrasonic standing waves in the air and the details of the sound pressure distribution, and the standing wave phenomenon and characteristics are difficult to understand in classroom teaching, the utility model provides a visual quasi-planar ultrasonic standing wave demonstrator and a method of use, which uses cold nitrogen mist evaporated from liquid nitrogen to intuitively and visually display the stereoscopic image of the quasi-planar ultrasonic standing wave, the positions and distribution of the wave nodes and antinodes, the sound pressure distribution, and the characteristics of the standing wave not propagating matter and energy. The three-dimensional ultrasonic standing wave can be observed from various angles, so as to understand the standing wave characteristics.

[0005] The technical solutions of the utility model are as follows:

[0006] A visual quasi-planar ultrasonic standing wave demonstrator is characterized in that it comprises an ultrasonic power signal generator, a base, an ultrasonic transmitter, a sound reflecting surface plate, a liquid nitrogen fogging cup, a lifting screw and a bracket, wherein the bracket is fixed on the base, the ultrasonic transmitter is placed on the base, the lifting screw is arranged on the bracket, the sound reflecting surface plate is arranged directly above the ultrasonic transmitter, the liquid nitrogen fogging cup is placed on the sound reflecting surface plate, circular small holes are evenly distributed on the sound reflecting surface plate and around the bottom of the liquid nitrogen fogging cup, the liquid nitrogen fogging cup is made of foam plastic, the output end of the ultrasonic power signal generator is connected to the input end of the ultrasonic transmitter, the upper surface of the ultrasonic transmitter is the sound incident surface, and the sound reflecting surface plate is the sound reflecting surface.

[0007] In order to avoid the interference of wind on the standing waves in space, the windproof glass can be arranged on the side between the sound incident surface and the sound reflecting surface; in order to make the standing wave image clear, auxiliary lighting can also be arranged.

[0008] The method for using the visual quasi-planar ultrasonic standing wave demonstrator is characterized in that the method comprises the following steps:

[0009] 1) Liquid nitrogen is filled inside the liquid nitrogen fogging cup, and cold nitrogen gas evaporated from the liquid nitrogen sinks along the outer edge of the cup body through the small holes of the sound reflecting surface plate into the space between the sound incident surface and the sound reflecting surface to form a mixed medium of cold nitrogen gas and air;

[0010] 2) starting the ultrasonic power signal generator to drive the ultrasonic transmitter to generate a quasi-planar ultrasonic incident wave;

[0011] 3) Shake the lifting screw to adjust the distance between the sound incident surface and the sound reflecting surface. When the distance between the sound incident surface and the sound reflecting surface satisfies an integer multiple of half the wavelength of the mixed medium sound wave, the cold liquid nitrogen mist clearly presents a stable quasi-plane standing wave stereoscopic image, sound pressure distribution contour, material energy non-propagation and other phenomena, and the visual effect is very obvious.

[0012] The technical effects of the utility model are as follows:

[0013] The visual quasi-plane ultrasonic standing wave demonstrator of the utility model is easy to operate, and can clearly present stable quasi-plane standing wave stereoscopic images and characteristics, sound pressure distribution contours, material energy non-propagation and other phenomena, which can easily attract students' interest and effectively assist in understanding the concept and phenomenon of standing waves, solving the problems that existing technologies such as Quint tube, Rubens flame tube, ultrasonic levitation, etc. are unable to present the stereoscopic images of ultrasonic standing waves in the air and the details of sound pressure distribution, and that students find it difficult to understand the standing wave phenomenon and characteristics in classroom teaching. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of a visual quasi-planar ultrasonic standing wave demonstrator.

[0015] Figure 2 It is a top view of the sound reflecting surface plate.

[0016] Figure 3 A stable quasi-planar standing wave pattern is formed between the ultrasonic transmitter 6 and the sound reflecting end panel 4 .

[0017] In the figure: 1- bracket, 2- lifting screw, 3- liquid nitrogen fog cup, 4- sound reflection surface plate, 5- windshield, 6- ultrasonic transmitter, 7- base, 8- ultrasonic power signal generator DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with an embodiment, but the present invention is not limited to the embodiment. Any similar structure and similar changes of the present invention should be included in the protection scope of the present invention. The use of directions such as up, down, front, back, left, and right in the present invention is only for the convenience of clear description and is not a limitation on the technical solution of the present invention.

[0019] Example

[0020] See also Figure 1 , Figure 1 It is a schematic diagram of the structure of a visual quasi-planar ultrasonic standing wave demonstrator of the present invention. As shown in the figure, the visual quasi-planar ultrasonic standing wave demonstrator of the present invention is characterized in that it includes an ultrasonic power signal generator 8, a base 7, an ultrasonic transmitter 6, a sound reflecting surface plate 4, a liquid nitrogen fogging cup 3, a lifting screw 2 and a bracket 1, the bracket 1 is fixed on the base 7, the ultrasonic transmitter 6 is placed on the base 7, the bracket 1 is provided with the lifting screw 2, the sound reflecting surface plate 4 is arranged directly above the ultrasonic transmitter 6, the liquid nitrogen fogging cup 3 is placed on the sound reflecting surface plate 4, and the sound reflecting surface plate 4 is evenly distributed with circular holes around the bottom of the liquid nitrogen fogging cup 3 (see Figure 2 ), the liquid nitrogen fogging cup 3 is made of foam plastic, the output end of the ultrasonic power signal generator 8 is connected to the input end of the ultrasonic transmitter 6, the upper surface of the ultrasonic transmitter 6 is the sound incident surface, and the sound reflecting surface plate 4 is the sound reflecting surface.

[0021] The visual quasi-planar ultrasonic standing wave demonstrator can be provided with the windproof glass 5 on the side between the sound incident surface and the sound reflecting surface to avoid the interference of wind on the spatial standing wave; and auxiliary lighting (not shown) can also be provided to make the standing wave image clear.

[0022] The method for using the visual quasi-planar ultrasonic standing wave demonstrator comprises the following steps:

[0023] 1) Liquid nitrogen is contained in the liquid nitrogen fogging cup 3, and cold nitrogen gas evaporated from the liquid nitrogen sinks along the outer edge of the cup body through the small holes of the sound reflecting surface plate 4 into the space between the sound incident surface and the sound reflecting surface to form a mixed medium of cold nitrogen gas and air;

[0024] 2) starting the ultrasonic power signal generator 8 to drive the ultrasonic transmitter 6 to generate a quasi-planar ultrasonic incident wave;

[0025] 3) Shake the lifting screw 2 to adjust the distance between the sound incident surface and the sound reflecting surface. When the distance between the sound incident surface and the sound reflecting surface satisfies an integer multiple of half the wavelength of the mixed medium sound wave, the cold liquid nitrogen mist clearly presents a stable quasi-plane standing wave with obvious visual effect.

[0026] Embodiment 1:

[0027] 1. Select and install a 28kHz, 100W ultrasonic transmitter 6;

[0028] 2. Adjust the ultrasonic power signal generator 8

[0029] The ultrasonic power signal generator 8 is connected to the ultrasonic transmitter 6, and the frequency of the ultrasonic power signal generator 8 is adjusted at about 28kHz, so that the ultrasonic transmitter 6 is in a resonant state, and a vertically upward quasi-planar ultrasonic incident wave is obtained in the space, corresponding to an ultrasonic wave length of about 12mm in the air at room temperature, that is, a half-wavelength of about 6mm. The ultrasonic incident wave is reflected back at the sound reflection surface plate 4, and the reflected wave and the incident wave are coherently superimposed to form a standing wave.

[0030] 3. Inject liquid nitrogen into the liquid nitrogen fog cup 3

[0031] Wear protective gloves, use the handheld liquid nitrogen metal dewar to slowly inject liquid nitrogen into the liquid nitrogen fog cup 3. The cold nitrogen gas evaporated from the liquid nitrogen in the liquid nitrogen fog cup 3 sinks along the outer edge of the cup body, enters the sound field space between the sound incident surface and the reflection surface through the small holes on the sound reflection surface plate to form a mixed medium of cold nitrogen gas and air.

[0032] 4. Adjust the height of the sound reflecting surface plate 4

[0033] The lifting screw 2 is rotated to adjust the height of the sound reflecting surface plate 4 to change the distance between the incident surface and the reflecting surface. When the distance between the incident surface and the reflecting surface satisfies an integer multiple of a half wavelength of the ultrasonic wave in the mixed medium of cold nitrogen and air, a stable standing wave is obtained, and the cold liquid nitrogen mist clearly presents a stable quasi-plane standing wave with obvious visual effect.

[0034] When the distance between the ultrasonic transmitter 6 and the reflective end panel 4 is about 73 mm, a stable quasi-plane standing wave with 12 antinodes is presented, and the distance between the nodes is about 6 mm, as shown below Figure 3 shown.

[0035] Embodiment 2:

[0036] 1. Select and install a 28kHz, 100W ultrasonic transmitter;

[0037] 2. Adjust the ultrasonic power signal generator

[0038] The ultrasonic power signal generator 8 is connected to the ultrasonic transmitter 6, and the frequency of the ultrasonic power signal generator is adjusted at about 28kHz, so that the ultrasonic transmitter is in a resonant state, and a vertically upward quasi-planar ultrasonic incident wave is obtained in the space, corresponding to an ultrasonic wave length of about 12mm in the air at room temperature, that is, a half-wavelength of about 6mm. The ultrasonic incident wave is reflected back at the acoustic reflection surface plate, and the reflected wave and the incident wave are coherently superimposed to form a standing wave.

[0039] 3. Inject liquid nitrogen into the liquid nitrogen fog cup 3

[0040] Wear protective gloves, use the handheld liquid nitrogen metal dewar to slowly inject liquid nitrogen into the liquid nitrogen fog cup 3. The cold nitrogen gas evaporated from the liquid nitrogen in the liquid nitrogen fog cup sinks along the outer edge of the cup body, enters the sound field space between the sound incident surface and the reflection surface through the small holes on the sound reflection surface plate to form a mixed medium of cold nitrogen gas and air.

[0041] 4. Adjust the height of the sound reflection surface

[0042] The lifting screw 2 is rotated to adjust the height of the sound reflecting surface plate 4 to change the distance between the incident surface and the reflecting surface. When the distance between the incident surface and the reflecting surface satisfies an integer multiple of a half wavelength of ultrasound in a mixed medium of cold nitrogen and air, a stable standing wave is obtained, and the cold liquid nitrogen mist clearly presents a stable quasi-plane standing wave with an obvious visual effect.

[0043] When the distance between the ultrasonic transmitter 6 and the reflective end panel 4 is about 121 mm, a stable quasi-plane standing wave with 20 antinodes is presented, and the distance between the nodes is about 6 mm. Figure 3 shown.

Claims

1. A visual quasi-planar ultrasonic standing wave demonstrator, characterized in that: The invention comprises an ultrasonic power signal generator (8), a base (7), an ultrasonic transmitter (6), a sound reflecting surface plate (4), a liquid nitrogen fogging cup (3), a lifting screw (2) and a bracket (1). The bracket (1) is fixed on the base (7), the ultrasonic transmitter (6) is placed on the base (7), the lifting screw (2) is arranged on the bracket (1), the sound reflecting surface plate (4) is arranged directly above the ultrasonic transmitter (6), the liquid nitrogen fogging cup (3) is placed on the sound reflecting surface plate (4), the sound reflecting surface plate (4) has circular holes evenly distributed around the bottom of the liquid nitrogen fogging cup (3), the liquid nitrogen fogging cup (3) is made of foam plastic, the output end of the ultrasonic power signal generator (8) is connected to the input end of the ultrasonic transmitter (6), the upper surface of the ultrasonic transmitter (6) is the sound incident surface, and the sound reflecting surface plate (4) is the sound reflecting surface.

2. The visual quasi-planar ultrasonic standing wave demonstrator according to claim 1, characterized in that: In order to avoid the interference of wind on the spatial standing wave, a windproof glass (5) can be arranged on the side between the sound incident surface and the sound reflecting surface; in order to make the standing wave image clear, auxiliary lighting can also be arranged.

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