The Visual Microphone: Passive Recovery of Sound from Video

"security cameras outside of stores" would be in public areas, yes? The Lifehacker link you pointed to says "Generally speaking, you have the right to record video in all public spaces without need of consent." Now for the fun part - it can be possible to extract audio from video, by careful processing of the small motions the sound induced in objects in the frame. See ▶ this video . High-speed camera is best, but at the end they show how a regular consumer-level camera can also be used.

with a high speed camera any vibrating reflective object like a potato chips bag can become a microphone: ▶ this video

Here similar experiment, 6 years ago: ▶ this video If you think that actual government agency cannot do even more easily with better equipment in 2020 you're kidding yourself.

You can do it with video too, even: ▶ this video Also, this is only tangentially related, but you can also see through walls using WiFi: link

See this - ▶ this video They show audio captured from a 60fps video from a DSLR exploiting the rolling shutter. I'm not sure if you can use less than 60fps though?

Remember even if you mute your microphone, it's still possible to extract audio from the video you are streaming: ▶ this video