The new "covert" made the object disappear
Author: Chang Lijun
the so-called "invisible" is not to be seen, but the naked eye can not be seen by the active sonar to detect its existence. According to the American physicist organization network in January 6th (Beijing time), a newly developed Illinois university laboratory has recently developed a "hidden voice coat" that can not be detected. In a paper in the Physical Review express, the researchers discussed it in detail that the object could be sold in sonar or other ultrasonic detects. A technique of hiding.
for many years, the materials that bend the sound of the object without reflection or absorption exist only in the theory, and there are many difficulties to be realized. "New technology is not science fiction, it's not Harry Porter's magic, but an acoustic mask," said Nicholas Fang, a professor of mechanical science and engineering at Backman's College of higher science and technology, who led the study. It can control sound waves by bending or twisting in a well designed space.
the enclosure is a well-designed sound circuit made of You Chao dielectric material. Metamaterials can enhance the characteristics and functions of the circuit structure. The cover is composed of concentric rings composed of 16 sound lines. Each ring has a different index of refraction, which means that the velocity of sound waves will change from the outer ring to the inner ring, which can guide the direction of the sound wave. "
" the cover looks like a series of tunnels connected by the tunnel. When the sound travels inside the tunnel, the cavity slows down the velocity of sound waves, "said Fang," and to the inner ring, the speed of sound waves is getting faster and faster. " But the acceleration needs energy, so that the sound waves will propagate along the outer edge of the outer cover and be guided by the sound lines in the tunnel. This special structure of the sound line will cause acoustic waves to warp and make it turn along the outer layer of the outer cover.
the researchers used steel cylinders to test the hidden noise enclosure. They sink the cylinder into the water tank, with an ultrasonic wave source on one side and a row of sensors on the other, and it disappears from the sonar detection after the cylinder is put on the cover. Further tests showed that the effect of the concealed sound on the different structures was the same.
another advantage of the mask is that it can cover a wide range of acoustic wave wavelengths, and the current silencing effect ranges from 40 kHz to 80 kHz, which will theoretically cover tens of megahertz.
the researchers next plan to expand the application of this stealth technology, from military covert operations to health care. For example, ultrasound and acoustic imaging techniques commonly used in medical treatment, such as bandages or shields made of metamaterials, can effectively shield interference.
Cain sound technology can also affect nonlinear sound phenomena. The problem of cavitation caused by the rapid movement of underwater objects, or the bubble and centripetal explosion, is widespread and difficult to solve. Researchers believe that the use of hidden sound can improve this.
editor in chief
Tang Zong and Chen Jingxuan in Changan were brothers, but they turned a blind eye to a beautiful woman. After breaking away from office, Chen Jingxuan became a Sichuan governor, while Zong fled to the Shu area in the chaos of an Shi. Zong's infamous wandering wandered around and was killed by Chen Jingxuan in Neijiang. The story of "disappeared" idiom recorded in the dream of the North just negates the possibility of extinction. No matter "hidden voice clothing" or "invisibility cloak", they are all aimed at existing sound sources or light sources. Therefore, in affirming the achievement of the University of Illinois, we should not expect the "unconsciousness of God" to be beyond the scientific expectation, and do not forget the lesson of a certain blood.