is there any way to charge cellphone or other devices by means of sound sensors?
Let’s put it this way: A dynamic microphone’s output is on the order of millivolts, at very little current. And that’s a relatively efficient transducer. If you’re willing to go _extremely_ low frequency, one can argue that wind is a pressure wave and so a windmill generator is a “sound sensor”. But that takes a much stronger signal before it starts moving at all. Maybe the sound from an explosion might move it a bit, briefly… Cellphones actually take a considerable amount of power. I have a hand-cranked generator which can be used to charge a cell phone in an emergency; its manufacturer says ten minutes of cranking may power a one-minute call. There has been discussion of trying to run some kinds of very simple, very-low-power circuitry from environmental energy sources of this sort. But even that is still theoretical. The practical answer is “No.
