Researchers from Sungkyunkwan University in Seoul, South Korea, developed an electronics charging system that uses sound waves as its power source. The louder the sound, the more charge gained.

The prototype can only convert sounds at volumes of around 100 decibels, which is about as loud as a chainsaw or jackhammer. The next phase of research will be to make the system work with quieter sounds, perhaps so that one day a phone could be charged simply by talking into it.