How loud is the Nex&?

Hi All,

I am considering getting the Nex7 to shoot inside a military acadamy classroom and am looking for something quieter than my Nikons and less obtrusive. I was surprised to hear that they may not be that quiet - as I wasn't sure what would be making that much noise in a mirrorless camera. Can anyone tell me how they might sound when compared to a Nikon DSLR (which to me are quite noise inside a quiet room...)? There are other reasons I am looking at the Nex7 for the same project as well, so this isn't the major use for the camera, but it would be nice to have a camera that worked in the classroom too. Thanks for any help you can give me.
Mark