How is this better than a solar-powered (USB) charger? E.g.: http://www.outdoorgearlab.com/Solar-Charger-Reviews/Buying-Advice http://www.outdoorgearlab.com/Sol

How is this better than a solar-powered (USB) charger? E.g.: http://www.outdoorgearlab.com/Solar-Charger-Reviews/Buying-Advice http://www.outdoorgearlab.com/Solar-Charger-Reviews/Buying-A... Light is a much better energy transmission medium than sound, it can be visible or invisible, focused, transmitted in a straight line (laser), easily routed via a simple mirror or encased in a glass fiber, and (with some notable exceptions) harmless. Also solar light is abundant during the day, as is indoor (albeit not nearly as powerful).