I believe it's all of the above, our boy covers his ears when we are under the fluorescent tube lights.. I think he/they are sensitive to the humm of the Ballasts..
It might also be the ultraviolet light that fluorescent light throw off, that is nearly unnoticed to most people, then there is the humming of the freezers, and Refrigerator units.. Our little guy hates to go down the Refrigerator isle..
I think this has some merit, because he has no such reaction in department stores, although they have their own drawbacks, crowds, narrow isles, and noise.. etc.. Ha! I have an example that you might try.. One day a couple of years ago, on a very unusually cold day, I bought him a cheap pair of earmuffs and he wore them in the store, and didn't react as he usually did..
That day, I also gave him my lightly tinted sunglasses and that seemed to work as well.. I can't tell which was better, because he wore both, but you might give it a try..
The new thing he likes is to sit under a folding table with a blanket over it, draped completely to the floor. I think it helps him block out all the distractions. He seems more at peace under the table than at almost any other time.