With Gerry I couldn't really tell if he was pecking or not, all I could hear was a sort of "wet paper bag" noise in the egg then one night I picked up his egg to whistle to him, had it up to my ear and CRRRRAAACK. Then he slept for the rest of the night and set about breaking the shell some more in the morning. All he was doing was pushing on the shell with his feet and beak rather than striking it.
They don't always answer back too, sometimes they're resting or sleeping or they just have a quiet personality.
Emu eggs aren't very vulnerable to the cold because they're so huge, and a highly developed chick ready to hatch is pretty good at keeping itself warm so you can have em out for around 10 minutes or so before you should put them back, plenty of time to have a whistle chat, watch em wiggle and listen through the shell.
If you hear a crinkly 'wet paper bag' noise inside the egg then that means the inner membrane has pulled away from the shell and they'll hatch very soon, took Gerry 4 days to pip, plus one more to hatch after he sounded. Just make sure they have enough fresh air and they'll hatch when they're ready.