I've noticed this with my bike as well... it's loud enough that I've had other bikers or pedestrians quickly shoot me concerned looks as I pass. And yes it does sound like a coffee grinder.. good description.

Chain is lubed. Chainline is fine. Chain isn't grimy. Chain is abolutely not too tight.. just the right amount of sag. Surly 19T rear cog. Sugino 48T front. No clue what chain, now that I think of it. We need a quiet-chain list..