My muscovy still doesn't make any noise, I think they hiss when they get mad but I've never heard it. My Pekins are so loud. They're always yelling at me about somethingThe drake Pekin has a very muted quack, he sounds like he lost his voice. Ducks are one of my favorites.
The female scovies that I had would trill it sounded like a whirring whistling sound. The boys would only hiss but were so much like puppy dogs I adored them. I was even known to take a nap in the yard with my boys lol.