Researchers in Japan and Germany have converted energy from soundwaves into electromagnetic energy, trapping a magnetic "spin current" between metal layers. In the experiment, when sound waves are directed at an interface between the thin metal layer and magnetic material, electrical signals are generated at a pair of electrodes attached above. When the soundwaves reach the magnetic material, this creates a spin current that gets picked up by three layers of metal. This is where the exercise class-sounding reverse spin Hall effect kicks in, transforming it into an electrical voltage.
At the moment, the project is looking into materials that are able to eke out more voltage from the process -- perhaps a few years later screaming at our phones will give their batteries a boost?