http://www.nikonchat.com/nikon-d5100-experience/

I wonder if this is common ..?
I’ve Nikon D5100
When I switch to live view. If I keep my ears near my camera I experienced some kind of sound, very low sound. If u switch TV then there’ll be some slight sound know like that.
I feel that sound from my camera only when place is clam!! Of if my ears go near camera. (Only during live view mode, I mean when lcd is showing live view)
Is my camera normal??
is this sound is due to lcd?? like all tv do..
I can’t speak for others, but when I put my Nikon D90 in Live View, I hear no sound in a quiet room even if I put it Record mode. If this concerns you, I’d contact Nikon about it, otherwise, I’d just ignore it.
Nikon D5100 Video Quality 1