I did not do my own oil change. I did change both the engine air filter and the cabin air filter. As I stated initially, the chimes started after I did the filter changes.
As per RobH, it's be the audio chime as you approach a spot. Just check the memory points in the navi unit.
The chimes are definitely not location related. They happen when I am near home and when I am far away from home. They surely have something to do with the filter changes. I may have to change the filters again with different brands to get to the bottom of this. I do appreciate all the suggestions. I am really surprised that no one has encountered this problem before. I then remind myself that only a very small percentage of Prii owners frequent this forum. Maybe I ought to get one of those PRIUSCHAT stickers for my car!