Also watch your response to sound...
Meowing is a instinctive juvenile cat behaviour to demand attention from their mother; adult cats rarely use it for communication amongst themselves other than when being sexual or territorial. Responding to mowling noises is an instinctive human reaction to distress of their offspring, and humans are hardwired to learn language. Put the two together and the cat learns that meowing is an effective strategy for persuading humans to provide food, scritches, door opening services etc, and the human learns the arbitrary[1] meanings of a handful of differently-modulated meows.
I don't know much about deaf cats[2], but cats of deaf humans learn that meowing is largely pointless, and develop alternative communication strategies based on head-nudging, Getting In The Way, pawing, repeatedly jumping against the window, etc, etc.
[1] IIRC the SCIENCE shows that the vocalisations are specific to the individual cat, but their own humans can consistently determine their meaning.
[2] Other than that it's surprisingly hard to perform a distraction hearing test on a cat, because they frequently can't be arsed.