This is different enough I’ll start a new discussion. In some cars, when you use the Bluetooth the phone conversation can be heard just as easily outside the car as inside. I assume those cars have speakers in the doors and there is not much insulation behind the speaker. You can only hear the other person speaking, not the one in the car. And it’s loud. The conversation I heard the other day could be perfectly heard 20 feet away at least.
The first time I heard this I was so startled I mentioned it to the lady, as she got out of her car while I was still parked. She looked at me like I was a stalker and didn’t believe me. She asked what she was talking about. I told her I wasn’t paying that much attention, but her daughter was on the other end and they discussed a birthday party. She was dumbfounded and just walked off. I never mention it anymore.
So if you use your Bluetooth in the car, you might want to have someone listen outside to see if your car does this.