Taxonomically, Harbor Seals (Phoca vitulina) are considered True or Eared Seals, and are members of family Phocidae. This differentiates them from the fur seals and sea lions (Otariids or Eared Seals) with whom they share the overall Pinniped super family. True Seals have no external ears, dense, short hair, internal or retractable reproductive organs, and are better suited to ocean swimming and endurance than the Eared Seals, though they trade off is a definite awkwardness on land.
|Image from Seal Sitters|
Harbor Seals are incredibly non-vocal. While I'm sure a lot of people think of loud barking when they think of any type of seal or sea lion, the Harbor Seal doesn't bark at all. Young pups have unique cries to tie them to their mothers, but beyond that, most of the seals' vocal communication is done underwater. Above water, physical communication is far more common.