Question about self defense, protecting yourself?

In the name of defending yourself, can you hypothetically speaking you know use a noise maker horn that you'd use at football games/ graduations and blow out someones ear drums if that person suddenly attacked you and tried to do you bodily harm and you happened to only have that on your person, would that be okay? They can't press charges on you because there there the one that came up on to you in your personal space right? As a matter of fact is any kind of self defense okay as long as you don't kill the person or is there a limit to protecting yourself with out out having charges pressed against you? BUT WAIT, if you smack an intruder in the head with a flashlight, and kill them, would you be charged for manslaughter if that person forced entree into your house? How far does self defense go?(These are all hypothetical questions by the way)