While your anecdotal stories are cute (please no offense, meant) I am seriously looking for a possible solution to the quacking.  Because of our living situation, my two runners Cuff (mama) and Link (Bad Duck) share my master bedroom with me.  I am an extremely light sleeper and Mama has started incessant quacking in the middle of the night and early morning (well before sunrise) She used to sleep through the night unless startled but now she wakes up and will not go back to sleep unless I let her out for a little walkabout.  My ducks are just under 2 years old and when we got them we thought we had two drakes... Mama stopped laying eggs about 3 months ago and both seemed to have lost interest in copulating but that too has increased in the last couple days along with the quacking.  No eggs have been produced yet, btw.  
 
I read an article recently that suggested that the same kind of bark control device could be used to control quacking.  The company Pet Safe offers a bird house looking device that when the dog barks, it will emit a high frequency sound the dog hears and trains the dog that his bark is causing the painful noise, therefore encouraging him not to bark... I have written the company to see if they have ever heard of anyone having success with ducks.  I am not aware of the frequency of sound that ducks hear, for example, humans cannot hear the sound emitted by the device, but dogs can.  Therefore, is it possible ducks too can hear it?  
 
As it seems now, the more I let Mama duck out of the cage in the middle of the night, the more demanding she becomes.  The idea of letting her quack herself to sleep like some might suggest to the parent of the crying baby does not seem to apply.  She seems to quack more and more and I sleep less and less.