Spaying Cats - a complete veterinary guide to feline spay surgery.
Scroll down to section 7
"7. Late onset complications or problems associated with spaying female cats."
It appears that leaving a bit of ovary can produce "a condition called a stump pyometron".
I had a female cat spayed in the 70s.
She was a cat I got from a sanctuary and was mute.
(Vet said she had probably been kicked in the throat.)
So I didn't get the problem you are having.
There are some videos on youtube of the noise you are referring to.