British physicists from the University of Bristol have developed an acoustic levitator capable of lifting and holding objects larger than a wavelength with a single ultrasonic beam. The authors announced the successful experiment a month ago in the pages of Physical Review Letters. Details of the study have also been published.
According to physicists, they managed to carry out the experiment, thanks to the creation of an acoustic vortex, which made a ball with a diameter of one and a half centimeters fly up and stay above the surface of the emitter. If you are not aware, then before the wavelength was a fundamental, fundamental limitation for single-beam acoustic levitators. Even earlier, the problem was the very creation of a levitator using a single beam. To obtain the effect, two sources of ultrasound were used. The topic seemed interesting and meaningful to me. Under the cut, more about the acoustic levitation of objects and the study of the British.
A few words about acoustic levitation
Wiki defines acoustic levitation as“stable position of a weighty object in a standing acoustic wave.”
This phenomenon has been known since 1934, when it was theoretically proved by L. King, later in 1961, conclusions about the possibility of the phenomenon were made by L.P. Gorkov.
The essence of the principle on which acoustic levitators work is to create interference of coherent sound waves, which leads to the appearance of local areas of pressure increase. Due to this, the body can be kept in one or another area of space, as well as move.
Scientists who deal with the topic of acoustic levitation believe in a great future for this phenomenon. Futuristic projects involve lifting and moving various objects, equipping warehouse management systems with levitators, and using them in ports and factories. However, levitators are still very far from such a mass and size. One of the areas where such devices can prove themselves in the near future is pharmacological technologies, where there is a need for acoustic levitation to increase the degree of purification of substances.
Lyrical digression
As a child, in the distant 90s, I happened to play the space civilization strategy Ascendancy. In it, the planets could be equipped with the so-called. tractor beam (capturing beam), which was able to attract objects from space. I was surprised when I lived to see the invention of a similar, albeit miniature, device.
How size didn't matter
Early single-beam acoustic levitators were developed by various scientists, incl. Asier Marzo from Bristol and Brazilian Marco Aurelio Brizzotti Andrade from the University of Sao Paulo. They were able to achieve the levitation of objects with a diameter of no more than 4 millimeters. The maximum size of objects that such a levitator lifted into the air should have been less than the length of a standing wave.This time, the Bristol scientists were able to overcome this fundamental limitation using a special emitter control algorithm. Thanks to the radiation control system, the hemispherical shape and the precise calculation of the power of ultrasonic radiation sources, it was possible to create acoustic vortices that can hold a large object. The new spherical levitator combines 192 ultrasonic emitters with a frequency of 40 kHz (wavelength at N.C. is 0.87 cm). The emitters are mounted on the inner surface of a sphere with a diameter of 192 mm.
Thanks to the ultrasonic signal control algorithm, several vortices with the same helicity and different directions are created. In the zone of their action, local areas of high pressure appear, holding the object. The maximum diameter of the ball that the Bristol apparatus lifted into the air is 1.6 cm, which is almost 2 times larger than the wavelength that the device creates. Also, the device is able to change the speed of rotation of the ball, by changing the direction of ultrasonic vortices.
Unexpected 2D Effects
Scientists' experiments have shown that when fixing one of the coordinates (for example, when the object is on the surface), the new design levitator is able to capture and rotate objects that exceed the wavelength by 5-6 times. This effect opens up new possibilities for the application of devices with acoustic vortices. They are supposed to be used to create centrifuges and laboratory systems for managing micro and macro particles.Outcome
The success of the Bristol team (Asier Marzo, Mihai Caleap and Bruce W. Drinkwater) indicates that acoustic levitators will likely be used in the near future for laboratory and later industrial applications.Perhaps, in the foreseeable future, acoustic levitation will be able to replace magnetic levitation, which is actively used today to create the original design of various devices, including speakers and turntables. It is possible that someday humanity will also see a powerful acoustic tractor beam (as in Ascendancy), capable of fixing and moving really large objects.
Although science has been considered the main paradigm of the development of human civilization for at least two centuries, the perception of the world by most people is still far from scientific. For example, such a phenomenon as acoustic levitation is outlandish for us. For everyday everyday consciousness, it is difficult to realize how objects can be made to levitate with the help of sound waves. Meanwhile, this phenomenon has been known, albeit in theory, to scientists for at least several decades.
What is sound
Actually acoustic, or sound levitation 
, that is, the stable position of an object with a tangible mass in an acoustic wave has a fairly simple explanation. To understand the essence of this phenomenon, it is enough to recall the nature of sound, which we have known since school days that it is a wave. Sound waves propagate in various media, be it a solid, liquid or heavy gas. The air around us is nothing but a heavy gas, or rather, a mixture of gases.
There is a special type of sound waves - the so-called standing wave. Such a wave occurs in special oscillatory systems, in which sound is reflected from a certain obstacle. In this case, the sound wave is not only reflected, but also superimposed on the original sound wave, and the positions of the maximum and minimum amplitude positions must be repeated. In real life, a standing sound wave can be heard and observed when playing musical instruments - such waves occur when air vibrates in an organ pipe or when a guitar string vibrates.
Levitation, that is, a kind of weightlessness area in which a material object can be placed, appears in this case due to the alternation of high and low pressure areas. Sound waves propagating in air are streams of molecules. Superimposed on each other in a standing acoustic wave, these molecular streams create rarefied zones in which the effect of gravity is significantly reduced. It is thanks to this that an object falling into a standing wave can actually hang, that is, lose its weight.
Vibration and reflection
In practice, however, so far, sound levitation can only be carried out with small objects and a small amount of one or another substance. It is also obvious that at the moment, acoustic levitation, recreated in domestic conditions with one's own hands, is a difficult task. Although with some luck, the necessary knowledge and the availability of the necessary materials and devices, such a result can be achieved. Most often, attempts to achieve acoustic levitation are made with a drop of water.
Any device for the implementation of this type of levitation must consist of a converting device with a vibrating surface that emits sound waves, and reflective surfaces from which these waves will “bounce”. Experiments show that it is most effective to give both the transforming vibrating surface and the reflectors a concave shape. Due to this, sound focusing is better achieved. In addition, it is necessary to pay special attention to the evenness of the transforming and reflecting surfaces and their correct location relative to each other. Because the sound wave must be reflected from the surface at the same angle at which it hits it.
Acoustic gravity is a promising area of research in the practical technological field, since it is almost independent of the materials used in the work, which reduces the cost of experiments. On the other hand, so far it has not been possible to achieve sound levitation with objects of significant mass, the weight of which is calculated in kilograms or more. In this case, strong sound waves are required to keep material objects in a state of weightlessness. Therefore, acoustic levitation is not yet very stable - if a sufficiently massive object is placed in a standing wave, then such powerful sound waves will be required to maintain it that their intensity can simply destroy the object.
The Swiss not only eat cheese, but also levitate
At the mention of Switzerland, the most common and understandable associations are the famous Swiss watches, banks and cheeses. However, fundamental science is actively developing in this country, so it is not surprising that successful experiments with acoustic levitation are carried out here. Local scientists in recent years have achieved the greatest success in this direction. Thus, specialists from the Swiss Higher Technical School (Zurich) for the first time managed to achieve a controlled flight of objects in the field of acoustic levitation.
The Swiss managed to solve one of the most tricky problems of sound levitation - the size of an object placed in a standing wave should not exceed half the length of the sound wave used. If the sound waves are too intense, then they are dangerous for the stability of the ongoing process. Scientists have developed an installation of many "converter-reflector" modules that balance each other. The emitted sound waves were changed with the help of a computer program, thanks to which it was possible to achieve control over a levitating object.
The researchers were able not only to alternately rotate a hung toothpick in different directions, but also to achieve a combination of solid particles in one lump and merging into one large drop of several small drops of water.
The problem of sound levitation is being developed not only in Switzerland, but also in the USA. Workers at the Argonne National Laboratory near Chicago have managed to carry out sonic levitation with biologically active materials. So far, this does not bring humanity closer to one of the cherished dreams of futurologists and science fiction writers - to a portable human levitation device. The achievement of American scientists is primarily associated with medicine and biology, as it helps to carry out various manipulations in more sterile conditions. However, so far this is only a promising development for the future - today the mass of a biologically active substance that can be manipulated under acoustic gravity does not exceed one milliliter.
Alexander Babitsky
Many modern researchers consider it a fictional version that the Egyptian pyramids were built using the manual labor of many slaves and hired workers. The fact that these huge structures were built by the Egyptians, and not by the highly developed civilization that preceded them, already raises doubts. Moreover, our civilization, with all its technological breakthroughs, cannot yet afford the construction of such structures.
Now the version is gaining more and more popularity that the multi-ton blocks of the Egyptian pyramids were stacked using acoustic levitation technology. The essence of this technology is that a standing wave arises between the ultrasound emitter and the reflector. It turns out that due to this wave, you can make some objects levitate.
So far, such experiments have been carried out only with small and light objects. But scientists believe that the acoustic effect largely depends not on the strength of the sound, but on its frequency. By selecting a certain frequency of sound, it is possible to achieve a state of resonance with a certain substance and cause a change in its properties, including the manifestation of levitation, in which the weight of the object is neutralized. And then it will not be so difficult to move multi-ton blogs.
Here is what Y. Ivanov, director of the Interdisciplinary Institute of Rhythmodynamics, writes about this: "Modern science is incapable of doing what was supposedly done by the ancient Egyptians. But the fact that large objects were moved by either acoustic levitation or some other method that we have little idea about, there is no mysticism here. there is an exact calculation and exact knowledge, that is, those who were engaged in this, knew what they were doing specifically, and were able to do it.
When an object has lost weight, you pick it up with one hand, like astronauts in space, and carry it where you need it. For example, you have a small device that allows you to do this. After that, you put it down carefully, adjust it, turn off the device, and this object regains weight and falls into place.
It was with the help of the method of acoustic levitation that Edvard Litzkalnen built his famous Coral Castle in the US state of Florida. For modern scientists, this stone castle, which took 100,000 corals to build, is still an engineering mystery. Since it is not entirely clear or, rather, it is not at all clear how the huge multi-ton blocks were ideally fitted to each other and stacked in towers, gates and other architectural compositions.
At the same time, it is known that before starting the construction of this castle, Litzkalnen spent a long time in the local library, where he studied books about the Egyptian pyramids with particular care. Some researchers believe that he managed to unravel the technology for the construction of these structures, based on acoustic levitation.
There is a photograph in the Coral Castle Museum, in which its former owner is captured at some kind of work. At the same time, strange boxes stand on tripods, from which some wires stretch to the blocks. And it is quite possible that these boxes served as signal repeaters of a certain frequency. He himself claimed that he played certain music to the stones, as a result of which, for a certain period of time, they lost their weight.
By the way, this technology is still known in some Tibetan lamaist monasteries and continues to be used in construction in highlands to lift heavy stones to a height by playing musical instruments. Therefore, there is nothing surprising in the fact that such technologies could be the legacy of ancient highly developed antediluvian civilizations, one of which the pyramids were built.
The pharaohs of Egypt, of course, no longer owned such technologies, but they tried to get to the technologies of the legendary "dynasty of the gods" that ruled these lands long before the pharaohs. Therefore, when these giant pyramids were discovered under the sands, they were dug out by order of the pharaohs. About what then the corresponding record was made on the walls of the pyramid. But modern historians interpret the names of these pharaohs precisely as the creators of the pyramids, despite the fact that the ancient Egyptians had no real opportunity to build such structures.
The same can be said about the structures of the "Incas" and "Maya", which in fact were created long before the appearance of these peoples themselves on the historical arena. And most likely, these complexes and pyramids of the American continent were created using the same technology that was used in the construction of the Great Pyramids of Giza.
British physicists from the University of Bristol have developed an acoustic levitator capable of lifting and holding objects larger than a wavelength with a single ultrasonic beam.
British scientists tm physicists from the University of Bristol have developed an acoustic levitator capable of lifting and holding objects larger than a wavelength with a single ultrasonic beam. The authors announced the successful experiment a month ago in the pages of Physical Review Letters.
According to physicists, they managed to carry out the experiment, thanks to the creation of an acoustic vortex, which made a ball with a diameter of one and a half centimeters fly up and stay above the surface of the emitter.
If you are not aware, then before the wavelength was a fundamental, fundamental limitation for single-beam acoustic levitators. Even earlier, the problem was the very creation of a levitator using a single beam.
To obtain the effect, two sources of ultrasound were used. The topic seemed interesting and meaningful to me. Under the cut, more about the acoustic levitation of objects and the study of the British.
A few words about acoustic levitation
Wiki defines acoustic levitation as
“stable position of a weighty object in a standing acoustic wave.”
This phenomenon has been known since 1934, when it was theoretically proved by L. King, later in 1961, conclusions about the possibility of the phenomenon were made by L.P. Gorkov.
The essence of the principle on which acoustic levitators work is to create interference of coherent sound waves, which leads to the appearance of local areas of pressure increase. Due to this, the body can be kept in one or another area of space, as well as move.
Scientists who deal with the topic of acoustic levitation believe in a great future for this phenomenon. Futuristic projects involve lifting and moving various objects, equipping warehouse management systems with levitators, and using them in ports and factories.
However, levitators are still very far from such a mass and size. One of the areas where such devices can prove themselves in the near future is pharmacological technologies, where there is a need for acoustic levitation to increase the degree of purification of substances.
Lyrical digression
As a child, in the distant 90s, I happened to play the space civilization strategy Ascendancy. In it, the planets could be equipped with the so-called. tractor beam (capturing beam), which was able to attract objects from space. I was surprised when I lived to see the invention of a similar, albeit miniature, device.
How size didn't matter
Early single-beam acoustic levitators were developed by various scientists, incl. Asier Marzo from Bristol and Brazilian Marco Aurelio Brizzotti Andrade from the University of Sao Paulo. They were able to achieve the levitation of objects with a diameter of no more than 4 millimeters. The maximum size of objects that such a levitator lifted into the air should have been less than the length of a standing wave.
This time, the Bristol scientists were able to overcome this fundamental limitation using a special emitter control algorithm.
Thanks to the radiation control system, the hemispherical shape and the precise calculation of the power of ultrasonic radiation sources, it was possible to create acoustic vortices that can hold a large object.
The new spherical levitator combines 192 ultrasonic emitters with a frequency of 40 kHz (wavelength at N.C. is 0.87 cm). The emitters are mounted on the inner surface of a sphere with a diameter of 192 mm.
Thanks to the ultrasonic signal control algorithm, several vortices with the same helicity and different directions are created. In the zone of their action, local areas of high pressure appear, holding the object.
The maximum diameter of the ball that the Bristol apparatus lifted into the air is 1.6 cm, which is almost 2 times larger than the wavelength that the device creates. Also, the device is able to change the speed of rotation of the ball, by changing the direction of ultrasonic vortices.
Unexpected 2D Effects
Scientists' experiments have shown that when fixing one of the coordinates (for example, when the object is on the surface), the new design levitator is able to capture and rotate objects that exceed the wavelength by 5-6 times.
This effect opens up new possibilities for the application of devices with acoustic vortices. They are supposed to be used to create centrifuges and laboratory systems for managing micro and macro particles.
Outcome
The success of the Bristol team (Asier Marzo, Mihai Caleap and Bruce W. Drinkwater) indicates that acoustic levitators will likely be used in the near future for laboratory and later industrial applications.
Perhaps, in the foreseeable future, acoustic levitation will be able to replace magnetic levitation, which is actively used today to create the original design of various devices, including speakers and turntables.
It is possible that someday humanity will also see a powerful acoustic tractor beam (as in Ascendancy), capable of fixing and moving really large objects. published
If you have any questions on this topic, ask them to specialists and readers of our project.
Sound travels in any medium except vacuum. Sound waves surround a person, but often he simply does not think about their presence. Sounds can be heard, but they are not tangible. Loud sounds have a negative effect on a person, create noise. Inaudible sounds can create sensations, but are not perceived by the human mind.
High-density sound can become tangible like an object. However, the laws of propagation of sound waves do not give an idea of sound as a driving force. What is felt objectively: the sound itself or the vibrations of surrounding objects?
The idea that such an intangible can lift objects may seem incredible, but this is a real phenomenon. Acoustic levitation uses the property of sound to cause vibrations in solids, liquids, and heavy gases. The possibility of producing an anti-gravitational force using sound waves was known in antiquity.
Acoustic levitation holds water drops.
The study of the phenomenon of acoustic levitation is based on the knowledge of gravity, air and the wave properties of sound.
gravity causes objects to attract each other. Newton's law is the simplest way to explain the nature of gravity. This law states that every particle in the universe attracts every other particle. The force of attraction increases with the mass of the object. The distance between objects also affects the force of attraction. At the planetary level, all objects near the surface of the earth fall to the ground. Gravity has its own parameters, which change little in the Universe.
In the air flows can also be created, as in liquids. Like liquids, air also consists of microparticles that move relative to the ground and relative to each other. Air can also flow like water, but since air particles are not highly dense, they can move faster.
Sound is vibration that occur in gas, liquid, solid medium. Sound waves propagate from a source that moves or changes shape very quickly with low amplitude. For example, striking a bell causes the bell to vibrate in the air. The bell moves to one side and pushes the air molecules, causing them to displace and push other molecules, creating an area of high pressure. Compressed air is generated in the high pressure area. As the bell moves back, it pulls on air molecules, creating an area of low pressure. In an area of low pressure, rarefied air is formed. The bell repeats the vibrating movements, creating a repetitive series of compression and rarefaction. The amplitude of the vibration of the bell determines the wavelength of the sound produced.
Sound waves are propagated by the movement of air molecules. Molecules located near the surface of the bell push the surrounding molecules in all directions. Sound propagates in the surrounding air. If there are no molecules, sound cannot propagate. This is why sound does not travel in a vacuum. The following animation depicts the sound generation process.
The bell pushes air molecules. Molecules push other molecules.
Sound waves are created by successive compression and rarefaction of air.
The sonic levitation method is based on the use of sound waves to balance the force of gravity. On Earth, this can lead to the effect of objects surfacing and floating above the Earth's surface. In space, this is a way of balancing and stabilizing objects in zero gravity.
Physics of sound levitation.
The acoustic levitation device consists of two main parts:
converter- a vibrating surface that produces sound waves;
reflector- the plate from which the sound wave is reflected.
The transducer and reflector may have concave surfaces to focus the sound. To hold a drop of water, the sound wave travels several times from the source to the reflector and back. The device is configured in a certain way: the ratio of the length of the gap between the transducer and the reflector to the wavelength is an integer. That is, the distance between the transducer and the reflector fits natural number of waves.
standing sound wave
The number of waves that fit into the gap
between the transducer and the reflector is equal to a natural number.
A sound wave, like all sounds, is a longitudinal pressure wave. In a longitudinal wave, the movement of each point is parallel to the direction of wave propagation.
The wave can bounce off surfaces. This implies the law of reflection, which states that the angle of incidence - the angle between the axis of the incident wave and the normal to the surface - is equal to the angle of reflection - the angle between the axis of the reflected wave and the normal to the surface. That is, the sound wave is reflected from the surface at the same angle at which it falls on the surface. Sound waves incident at a 90 degree angle will be reflected back at the same angle.
When a sound wave is reflected from a surface, the interaction between its concentrations and rarefactions creates interference. The compressions of the sound wave meet the compressions of the reflected wave. In order for the wave to stand still and not move, the wavelength must fit an integer number of times in the gap between the transducer and the reflector. Thus, closed areas of dense air and areas of rarefied air are created. Using standing sound waves, a drop of water can be suspended in the air.
Standing sound waves have nodes - areas of minimum pressure - and antinodes - areas of maximum pressure. In order for a drop of water to levitate, it is necessary to place it in the node of a sound wave. The drop will lie between two antinodes.
Areas of low and high pressure
A standing sound wave forms
areas of compressed and rarefied air
The reflector is installed with respect to the transducer in such a way that an integer number of wavelengths fit into the distance between them, and the areas of low and high pressure are parallel to the axis of gravity. In this case, the sound wave creates a constant pressure on the water drop from below and balances the force of gravity.
A drop of water is located in a node
Acoustic levitation creates areas
high pressure that hold water droplets
There is weak gravity in space. Floating particles are collected in the nodes of sound waves and do not scatter. Under the conditions of terrestrial gravity, the particles are located above the antinodes, which prevent the particles from falling to the ground.
Acoustic levitation can be applied in various fields: control of airborne particles, weight lifting, stabilization and coordination, positioning of parts, devices in production, control of liquid substances.
The principle of acoustic levitation is to produce sound waves in a closed area. Due to the compression and rarefaction of air by sound waves, areas of low and high pressure are formed - nodes and antinodes of a standing sound wave. The gravitational force acts in the nodes: air particles and suspended microparticles tend to the center of the node. Antigravity force acts in the antinodes: air particles and suspended particles tend to leave the antinode.
Similar experiments can be carried out in a magnetic and electric field to overcome gravity and balance objects in a levitating state.
