When should i hear peeping?

[ducklover101202]

I have duck eggs day 23. I only have 3 that are all alive still in a home-made incubator. Two of them starting moving the egg day 20 to 21. They keep moving the egg. I am turning them still. It isn't harming them. They are still moving the egg a lot. What does this mean? Is it just because they are moving in the egg or they are getting into position. When the moving of the egg starts, when should I start to hear quacking?

 

[SarahFair]

Ive never hatched ducks so Im not sure. There was a couple of threads earlier last week on the topic..
Maybe do a search?