weird whining noise

[RPSilvia]

there is a weird whining noise coming from the right side of the engine(intake manifold side) it happens out of nowhere but also goes away in like 5-10 mins. it also happens whenever i start up the car, never while driving and also drops my battery voltage down into the 11s when its idle but raises back to 12-13 when cruising. the weird thing is after i turn off the car it still makes that sound so i dunno what it could be. alternator going bad? anyone got any ideas?

thanks