MIT Technology Review January 28, 2019 To send the messages, researchers from MIT Lincoln Laboratory relied upon the photoacoustic effect in which water vapor in the air absorbs light and forms sound waves. The researchers used a laser beam to transmit a sound at 60 decibels (roughly the volume of background music or conversation in a restaurant) to a target person who was standing 2.5 meters away. A second technique modulated the power of the laser beam to encode a message, which produced a quieter but clearer result. The team used it to beam music, recorded speech, and various tones, […]
Tag Archives: Acoustics
Revealing hidden information in sound waves
Phys.org November 29, 2018 Sonar arrays are typically designed to record sounds in specific frequency ranges. Sounds with frequencies higher than an array’s intended range may confuse the system. Researchers at the University of Michigan have developed a technique that will allow just about any signal to be shifted to a frequency range where sonar arrays are no longer confused. It mathematically combines any two frequencies within the signal’s recorded frequency range, to reveal information outside that range at a new, third frequency which is the sum or difference of the two input frequencies. The additional information could boost performance […]