Alternator whistle sound

Hey guys sorry I've been MIA been busy for me. Anyways got a new voltage regulator and my voltage stays right where it needs to be. 13.8-14.5.
The odd time when car is hot and fans on at idle it gets down to 12.8 .....

I'm still getting the whistle at around 3000 rpm. Quite loud. And when I rev and it comes back to idle you will hear a quick whistle.... also at idle the headlights and tail lights strobe. The strobe gets faster with rpm.
I've checked all my grounds and so far I haven't noticed anything bad.