I think Zamarran noticed that her attention was directed to the front of the bridge
He's a perceptive fellow
Given K&K friendship, plus her distraction from work and attention targeted at the occupant of the comm console, he "did the math"
As for the sounds of Cardassian... Well, it is not just foreign language, it is a foreign species
language based on non-mammalian biology. I guess their language can have anything in it