+2 or 3 on Capt. I would wait. If there were more noise, call 911. Then wait some more. If no more noise? Now it gets tricky/scary. What kind of noise was it? Was it something I could explain? Was it a noise that sounded like a forced entry? How long should I wait? Wake/gather the kids? More firepower? Wife backup? Get my jeans on? Electronic ear muffs?
...There just doesn't seem to be any guarantees in living.