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 in that store. The problem was that there were two radios going, they were set to different stations, and no one could figure out how to make the cacaphony stop.
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 I soon stopped rocking and smacking. I had my behavior under control, but I was far from all right. Because I was filled with an irrational rage. There was nothing to be angry about, and I knew it, but I was very angry at the music that was still playing, even though I'd been enjoying it just a few minutes earlier. I was angry at the manager's polite apology. A quiet conversation between a mother and her child infuriated me. And it seemed like there was an unreasonable, maddening 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 an off switch, just pull the plug.