I chop my own full length feathers and grind my own natural turkey feathers, then chop all of them shield cut 4.75" and I have not noticed any noise at all with factory full length feathers or adult turkey wing feathers.
I did have some that whistled when they flew, but they were off of a young bird. The feathers are too thin unless the bird is mature like a gobbler or old adult hen. Then they are whisper quiet.
I've also fletched parabolics and they are really quiet, but the longest I have fletched in those is 4"
I actually found that carbon arrows make more shaft noise than the feathers do, but my woodies make no noise at all. I think the woodies actually help deaden the noise of the bow some also.