Do you happen to have a wireless doorbell? Reason I ask, we live on Pearl. Traffic isn't bad, but it's busier than most of our streets. That was happening to us sometimes, and it was driving me crazy. Then one day I was standing in the foyer when a car drove by and the doorbell went off. Somehow a device in the car or something set it off. Same frequency or something. I wasn't sure if that was a coincidence until it happened a 2nd time.
I'm no techie, so I could be wrong, but that's what I figured.