I love my Cayuga pair. They CAN fly, but they don't. Their feathers are that black, so black it's beetle green in the sunlight. Mine are REALLY quiet. I think I hear Thelma quack maybe once or twice a week - and it's a single, loud quack only if somebody has ticked her off. (It only takes the one quack for my dachshunds to get the heck away from her.)
Louie gabbles all the time, talking to me, telling me stories, and murmurring to Thelma, but the sounds are very very low, not distinct quacks at all.
Louie is friendlier than Thelma, but she's just being a Diva. Once I pick her up, she's calm and friendly.