I've been different with all of mine I screamed with my second just as she was about to be born but as I went from not in labour and 2 cms to giving birth in 23 mins I think that was just because it was so intense, I didn't need to concentrate on pushing because I only pushed a couple of times and she was out I got told to be quiet that time (not that I took any notice ) but honestly didn't realise at first that it was me making the noise
I think everyone makes some sort of noise while pushing , and cow type noise or loud gruntings normal because of the effort involved, but when you scream I think it perhaps doesn't help you feel as in control so i tried not to do it in my other labours and with my last natural birth I was really quiet
But if you feel it helps, then sod it, scream the place down I say xx