Aaaaahhhhhh!!

Yes, but instead of passing it through an amp to speakers, it stores the energy in a battery

So, one dad sneeze and you'll light up the entire town

Not hating on them. I’m sure there is some novel thing in their design- but we can already convert sound to electricity, not in the “microphone” way- but an actual power source. Many ships use a similar technology to communicate on board without power. The receiver generates enough power to both provide audio signal and carry the signal. The technology here is likely some form of vibration powered generator. Commonly using a resonator and transducer to produce power. It’s not a new idea, although until fairly recently the technology to make such a device which could provide meaningful use has been largely lacking.

There are technical challenges having to do with things like batter life and the generated charge etc. which have tended to make this technology less versatile than a more traditional system such as mechanically driven or combustion powered small generators. Service life, use, lots of factors. It’s a neat idea with potential. Water has been explored as a means to provide the vibrations where said water source lacks suitability for turning a mechanical flywheel or turbine, or thermal energy generation, or kinetic through wave capture etc.