It varies with each hen. We have some that they are in the nest 5 minutes and others that you would think they were taking up residency. And then, every so often we have a girl that doesn't quite make it to the nest. But on the average, our girls will sit in the box for about half an hour.
Then for the song... We have a couple of girls that let everyone know they are going in to lay an egg and really let everyone know when they come out. We also have a few girls that think they are stealth layers. Not a peep.
So all and all it just depends on the hen
What age and breed do you have?? I have some that sing the 'egg song' before they lay--while they are getting into the nest box but nothing after... I have some that sing when she is finished and I have one that just lays her egg, gets out of nest box and shakes her tail (like you see a duck shake his -- from side to side)...