You heard your neighbor’s back up camera making the beep beep too close warning sound. Many of the newer cars do this, which may explain your hearing it before. It’s a nice feature!
So, I am puzzled. I was backing out of my driveway today and my neighbor across the street was coming out of his driveway too. I didn't see him but my car gave me two beeping sound which was kind of weird. As far as I know, my has no back-up sensors of any kind. Almost 15 years I own that car, I think I heard it once before. I can't find anything on Google. Was I imagining this?? I hope I am not going nuts. Experts, thoughts?