By far Muscovy are the quietest. As far as mallard derived breeds go I think Silver Appleyards are quiet and my Ancona's only make noise when hungry of scared. I have very little experience with runners but from what I know they are very nervy and can be quite loud.
I have six runners, and if you leave them in the cage the hens will be loud until I let them out. Once I let them out they will eat and play in their kiddie pool and you wouldn't know I even had ducks. So as long as I let them out in the morning they are quite.
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I have anconas also and they are pretty quiet... My blue swedish hen is really really LOUD I can hear in the house like she is sitting right beside me
The loudest duck I ever had was a buff. I sold her to keep my neighbors from coming for me with torches and pitchforks. The loudest duck I have now is my Welsh Harlequin Lexus. The other 2 Welsh Harlequins aren't that bad but she is a big mouth. My runner is pretty quiet.