I was just at a friend's house a few minutes ago to witness loud blending. He just has some Oster model, though it's pretty nice despite the low-end brand. It was crazy loud just going through a banana, some strawberries and some milk. I imagine running it empty would only have made it louder, as there would be no mass in the beaker to slow the blade and absorb the sound waves from within it. The motor itself was super loud.

I don't think I'll buy a blender until I decide to grab a Blendtec. It was already between that and Vitamix years ago anyway.