In a similar vein I note that many cars broadcast the Bluetooth phone conversations within to the public. This is because they use the speakers in the door and that particular car has poor insulation behind the speaker. I was walking to the store once and this woman’s conversation was so distinct I heard it from several cars back until I had passed her and was heading to the store. She got out of her car right then and I awkwardly tried to explain to her that her car did this and that she was probably not aware of it.
She snarked back, “Oh, really? What were we talking about?” I replied, “you and your Mom were planning a birthday party for someone”. Her jaw dropped and she hustled off like I had done some kind of a magic trick.
You can only hear the person in the car, not the voice of the other person on the phone.