Sexing ducks

I am needing help in sexing my blue swedish ducks. I can't remember which quack is a duck and which belongs to the drake. Any help would be appreciated!

Quack is the female! (figures huh?)

So what does the male get, "quirk?"

Males are very low and raspy sounding. The girls are way louder and there is a very distinct difference more of a rrrhhht rrrhht sound than quack. If you pick up one duck and walk away from the group and then just listen because they will start just making a ruckus. By the time they have they're chest and the start of their back feathers you should be able to sex them by voice. Grab a chair and a cup of coffee and just watch and listen for a bit as they chatter to each other you'll figure it out. Usually the males don't talk as much. Someone posted a link awhile ago to majesticwaterfowl sanctuary and they have audios of the male and female duck sounds. The male is hard to hear with the crickets or whatever it is in the background but the female is easy to hear. Good luck

Thanks all, I think when I move them to their permanent pen will be easier to figure things out at least with a couple!