I have some age-related hearing loss. Our dog has taken it upon himself to let me know when anyone is on the property. He does get confused, though, by sounds of doorbells and cellphones on TV. He will run to the door and the large windows overlooking the driveway, barking like crazy and looking for the *visitor*.
If a friend comes into the house, he will not let them past a certain point unless I specifically tell him it’s ok. He just stands rooted like a statue and blocks them, gently, until I come over and tell him to let the person pass further. At 115 pounds, no one argues with him.