Hello, Elle!
I think the "Cottingley Fairies" story is fairly well known.
Conan Doyle believed the girls, as I remember?
I can not quite remember if the photos were examined by photographic experts, and said to be genuine?
But it's a few years since I read the book.
I would say "quietened" is a word, but "quieted"?
Ah, yes, it is in Collins online, as a past participle.
Is that fine?