Sperm whales.

Originally shared by David Brin

Sperm whales. Among the most fascinating creatures ever, on this planet.  This article (accompanied by an amazing photo) describes researchers who free dive with these titans, correlating sonar expressions with behaviors.  
“When their clicks are viewed on a spectrogram, a visual representation of an audio signal, each reveals a remarkably complex pattern. Inside these clicks are a series of shorter clicks, each lasting a few thousandths of a second, and so on.Mr. Schnöller and Mr. Buyle believe that sonar artifacts (like images) might be embedded in these vocalizations — that because these animals are already viewing their world through echoes, they may also be able to send these echoed images to one another. They’ll test the theory by capturing these clicks, sending them back to the animals.”  (Might I add that this notion of communicating via sound-sculpted imagery was in both Sundiver and Startide Rising?)
 
http://www.nytimes.com/interactive/2016/04/16/opinion/sunday/conversation-with-whales.html?ref=opinion&_r=0