I have heard the buzzing noise in both of my NDEs. I interpret it as literally the "noise" of your consciousness you can only hear when your brain is getting "no signal" from your ears and begins to interpret what used to be filtered out, an electric noise.
I think the "vibrational" in "higher vibrational state" doesn't mean the type of thing that makes a noise as it vibrates... but at this level, I don't think "hearing" means what it normally means...