I got this idea; instead of using a microphone and preamp at the end of a twisted pair, I would build a microphone, preamp and modulate a red laser with the audio and pick up the audio about ten yards away with a light detector.
Notice that it runs on two 2V photovoltaic cells in series which charge up six .022 Farad supercaps in parallel to supply power if a cloud obscures the sunlight.
I could use another solar cell to detect the laser beam. Or else a photodiode or phototransistor. I have also used a LED as a light sensing diode. I’ll then amplify the light beam to a usable signal.
Update: I’m using a telephone earphone element and a 50mm square solar cell from an old garden light, and when the laser beam hits the solar cell, the audio is clear but actually a bit loud.