my fawn and white runner can be very loud. I can hear the duck quacking downstairs when i'm upstairs. It's like a loud like a dog bark... like: Wuah-wuah-wuah over and over until you tend to them. If they have enough food, water, kiddie pool water, things to play with, and you stick to your schedule they don't quack loudly often. Ducks seem to be able to tell time and notice when their schedule is off... I give mine food at 6am everyday and will quack until i get up to feed them.
If it makes you feel better, My ducks live in my backyard and in my house. they never bother me more than a loud tv when inside. my nieghbor's have never complained (but they don't quack outside often). I did once have to take them on a trip with me to atlanta for two nights. they stayed in the bathroom and got baths, and had feed all the time. I put the tv and do not disturb sign up when i left the hotel room and i had no complaints... no one even knew we had the ducks with us...
All ducks quack (minus the muscovy) and if your neighbors are hellbent on being jerks about it, consider your duck being in the garage/house if you can't be outside with it... or be okay with possibly giving up your ducks to the authorities...