New PSU RM650 a little Coil Sound

My new PSU when I play I hear a little sound of Coil :sigh!:



Everything works perfect,it's very quiet





When I play game or benchmark I hear a little sound ñiiñiñiñiñiñ :bigeyes:



Today my friend buy other RM650 and his PSU have the same sound :eek:



Is this normal? is it dangerous?



Thanks :cool: