Hmmm. Never heard of such a thing, but I imagine that "common sense" application would be more important than whatever your state's law has to say. In a rural area that doesn't bat an eyelash at a gunshot, it's probably no problem.
Be wary of "no discharge" ordinances...not sure if these apply to blanks.
Reminds me of the old "spring gun" cases from my civil torts class. Although those were live ammo...ouch.