Here are two underwater recordings made by dolphin researcher Pieter Arend Folkens. The second is of a group of bottlenose dolphins in the Sea of Cortez. Listen to killer whales. This is a small pod of killer whales, including a calf.
Echolocation begins with a series of clicks that accelerates into almost a buzz.
Finally, you'll hear a repetition of a whistle, which is likely the signature social call of this particular pod. Listen to dolphins. It's not unlike being in the middle of a meeting hall during a family reunion. Everyone is talking. In this case, it's hard to distinguish any one voice, but there's no question that a lot of conversation is going on.