Grunting baby

So i know grunting and straining is normal & has to do with baby getting used to his digestive system. But it seems to be more prominent if i put him in his crib. He eventually settles down on his own. When he falls asleep on my chest or in my arms, he only grunts & strains when i move otherwise he’s quiet. He’s a noisy sleeper in the crib but quieter on me. So if its a digestion thing how is the noisiness based on where he is sleeping? I dont get it. Anyone know why?