Yes. I scrolled and found it by chance: "Simply put, your brain is trying to figure out what it’s hearing, so it’s filling in the gaps of the noise you’re listening to with a common sound."

Cmd+f found no mention of AM radio in there, which is another possible explanation for hearing voices or music in those machines. If I were hearing that, I wouldn't appreciate this article telling me it's in my head.

Agreed. I always read the first few paragraphs then see that I'm not even 1/8th of the way down the page but have gotten all of the info I need and click off and read HN comments.