Once upon a time I could rely on my canine early warning system to alert me to distantly ringing doorbells, arriving delivery trucks, and just about anything else that he considered a threat or an intrusion. Even a doorbell on the radio or television that sounded like the real one would set him off.
In recent months, however, little Elo is slowing down a bit, losing his edge in the hearing department. Several times the doorbell has rung while I've been in the basement and he's not even aware of it. I've taken to keeping an ear out and have even myself wandered upstairs (thinking I've heard the bell) to find nobody there.
So I've scouted out the doorbell wiring (running openly in the basement ceiling) and DIY help on adding a second chime (I'll need to use the existing wiring as a pull wire to run a second feed from the old chime to the new chime)
But pretty simple stuff. I might even do a little audio browsing for a more mellow chime and buy two of those, and replace the more traditional "ding-dong" chime that came with the place.