If street noise worked for me I'd mount a weatherproof microphone outside the window, run a cable from it inside (maybe around the edge of the window) to a preamp driving a cheap Class D power amp, and drive one good speaker with it. Maybe put a graphic EQ in the chain after the preamp if I wanted to fiddle with the sound.

Winter problem solved. No bluetooth or batteries needed; just a wall wart or maybe USB-C.

Running the cable would be the trickiest part if I had close tolerance metal window frames. In that case maybe a bluetooth mic would be best, but I'd have to figure out how to weatherproof it.