I sniffed the flowers and ... eeeewwwww! They don't smell nice.
These are Callery pears whose most common cultivar is called the Bradford pear. Originally from China, they're bred for their pleasing shape and size, beautiful flowers and red autumn foliage. They always look good and looks count more than scent, so the breeders didn't bother to try for sweet-smelling blossoms.
Their scent must appeal to something because the trees produce small hard pears that the birds eat after frost softens them. I imagine the pollinators are flies attracted to unpleasant, slightly putrid smells... but I don't know.
So enjoy the flowers. Look, but don't smell!
p.s. Choke cherries are starting to bloom in the woods and along our hillsides. They smell nice!
(photo from Wikimedia Commons. Click on the photo to see the original)