From the NMMFoundation:
A new paper published by the National Marine Mammal Foundation in the scientific journal Current Biology sheds light on the ability of marine mammals to spontaneously mimic human speech. The study details the case of a white whale named NOC who began to mimic the human voice, presumably a result of vocal learning.
"The whale's vocalizations often sounded as if two people were conversing in the distance," says Dr. Sam Ridgway, President of the National Marine Mammal Foundation. "These 'conversations' were heard several times before the whale was eventually identified as the source. In fact, we discovered it when a diver mistook the whale for a human voice giving him underwater directions."