After the government started to cut major social network platforms access, Occupy Central, Hong Kong protesters turn to mesh networks to evade China’s censorship http://www.extremetech.com/extreme/191118-hong-kong-protesters-turn-to-mesh-networks-to-evade-chinas-censorship
The 'sonoluminescence' is the phenomenon, discovered in 1929 by H. Frenzel and H. Schultes, which chemically converts the sound into light. The (accidental) discovery revealed that dissolving oxygen in water, this brightened if irradiated by ultrasonic signals sufficiently strong, because the bubbles formed inside to collapse the pressure of the liquid and release for a time infinintesimale the energy in form of light. Just this phenomenon is exploited by the installation Camera Lucida by Evelina Domnitch and Dmitry Gelfand who made a clear container filled with liquid gas, attaches them to the walls, eight ultrasonic translators. These generate a range of frequencies made visible as they pass through the medium of chemical they meet in their propagation. This visualization of sound is closely related to the invisible physicality of it, and faint flashes that active illumination of a presence that would otherwise be exclusively linked to our ears. This interpretation chemistry (which gave off a branch of study called, precisely, 'sonochemistry') shows the waves as they pass, giving a 'shadow shiny' to their ethereal intangibility.