All the cats I have had over the years had several distinct noises
they would make.

Meow -- Used to train their humans.
Purr -- Satisfaction
Growl -- Fighting
Snarl -- Fighting, usually accompanying the growl; also used when
making love with another cat
Low gutteral meow -- Pain

It's pretty hard to miss the meaning of the low gutteral meow. If
you've never heard it, you and your cats are lucky. Come to think of
it, I've had  a couple cats who never used it, both females. All the
male cats I can think of would use it, though. My old cat (died in
2001) used to use it to let me know when he was hurting. Toward the
end of his life he used to get gas, usually in the middle of the
night. I would wake up to find him on the bed with me, giving me the
low meow. I'd pet him and rub his tummy, then, suddenly I would smell
the odor as he passed gas, whereupon he would lie down and go back to
sleep.

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