I am reasonably certain the cell phone "trap" exists, and that I have read
about it, but I don't remember any details. It was for a place like a large
indoor theater, or some such where it was quite reasonable to forbid any
cell phone usage.
RE boomer cars
The basic problem is the inverse square relation between distance and spl,
means you are going to need to make HUGE amounts more sound in your car
before the boomer guy would ever hear ANYTHING but his own system.