![]() More importantly, the trained network provides insight into the dynamic behavior of matter including quantitative measures of the scattered field sensitivity to each material property and how the sensitivity changes depending on the material under test. Furthermore, networks trained with synthetic data can process physical measurements and are very robust to measurement errors. Here, we show that convolutional neural networks can interpret the diffracted fields and learn the mapping between the scattered fields and all the effective material parameters including mass density and stiffness tensors from a small set of numerical simulations. These methods show their limitations in scenarios where the analyzed medium is moderately sized and the diffraction from the material edges influences the scattered fields significantly, such as non-destructive diagnostics and metamaterial characterization. This "acoustic assault rifle" is shaped like a gun, but instead of bullets, it dispenses high-decibel sounds that would cause discomfort or even pain.Conventional methods used to identify the dynamical properties of unknown media from scattered mechanical waves rely on analytical or numerical manipulations of the wave equation. ![]() Small transmitters could be kept out of sight, and ghost sounds could be bounced off "rocks or any reflective surface" to fool people into believing they were not alone.Īmerican Technology is also working on a stronger version of the technology called Directed Stick Radiator, Croft said. Army to develop the technology for a decidedly non-commercial use: psychological warfare.Īccording to American Technology CTO Jim Croft, the technology could be used to confuse opponents by making them think there was someone nearby. "It's remarkable, a spectacular effect."Īmerican Technology president Terry Conrad said the company is going into its first mass production of chips that convert the audible sounds into ultrasonic waves in February.Īmerican Technology recently signed an agreement with the U.S. The HSS system similarly converts audio into ultrasonic sound waves, and Blackstock was impressed by a demonstration.īlackstock said he heard a clear signal at about 100 meters, but then heard nothing by moving two steps out of the audio's path. Pompei started Holosonic Research Labs to sell Audio Spotlights to corporations such as Kraft and Kodak, which are in the process of integrating them into information kiosks and retail displays.Īn alternative to Pompei's invention, which also may be commercially available soon, is American Technology's Hypersonic Sound System. Pompei said Audio Spotlights are currently being installed in Australia for the upcoming Fringe Festival. Blackstock said ultrasonic signals "decay more slowly than lower-frequency waves" so they are easier to send farther.īlackstock said the first experiments to use ultrasonic sounds were conducted underwater in the 1960s, and Japanese researchers made advances in the 1980s but were unable to create a commercial application for the technology. He wrote algorithms that "reverse-engineered" the desired sound waves to determine the appropriate ultrasonic source signals.Īccording to University of Texas professor David Blackstock, high-frequency signals are easier to focus, and control like a flashlight, than sounds that are within the human range of hearing, which disperse in all directions. Pompei said the "non-linear" effect of air pressure modifies sound waves in a consistent fashion. As these sound waves push out from the source, they interact with air pressure to create audible sounds. The Audio Spotlight converts ordinary audio into high-frequency ultrasonic signals that are outside the range of normal hearing. "It could make for much happier trips," he said. ![]() He put several Audio Spotlights in a concept truck from Chrysler, which enabled passengers to hear their own radio stations - the kids in the back seat enjoyed heavy metal while the parents relaxed to elevator music. The technology could also be used to prevent fights over the car's radio tuner, Pompei said. The Audio Spotlight transmitters range from several inches in diameter to about 20 inches and generate a column of sound between one to three degrees wider than the transmitter. He said museums like the system because visitors who stand in front of an exhibit can hear the appropriate audio track without being distracted by sound from other displays. Pompei developed the first demonstration systems of the technology for installations at Sega's Joyopolis theme park in Tokyo and the Boston Museum of Science, and he's planning to start selling it commercially soon.
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