The problem probably started when someone designed a radio with no obvious "off" switch. I don't know if that's the reason the radio ended up in a second-hand store, but it's probably the reason a customer turned it on to check it out and then walked away, leaving it on, and it's definitely the reason an employee couldn't figure out how to turn it off while his manager was shouting, "Turn it off! Just turn it off!" and I was smacking myself in the head and rocking back and forth.
I am perfectly fine with a radio in a store. In fact I usually enjoy listening to the radio that comes from the speakers in the corners of that particular store. The problem was the radio in the center of the store that was set to a different station with the volume turned up too high and no apparent off-switch. Anyone would have trouble with that.
The employee finally gave up looking for the off-switch and turned the dial to the station that the store-radio was set to, and with the cacophany stopped, I got better quickly. But I was irrationally angry at the music that was still playing, the manager's polite apology, the nearby conversation between a mother and her child, and the unreasonable distance separating me from my car.
Getting the environmental sounds back to normal helped, but it wasn't enough. I needed silence and home. It's sort of like after someone has been sick; we don't expect them to immediately bounce back into an active life-- we understand if they need a day or so of light activity to regain their strength. So if you have a child who can't handle certain noises, after you get it turned off, please give the child some quiet recovery time.
And if you can't find the off switch, for crying out loud just pull the plug.