Next fall, a team of documentary filmmakers and scientists will head out into the North Pacific in search of a whale.

They know which whale they’ll be looking for, although nobody is completely sure what species it is. It may be a blue whale, is more likely a fin, but could be a hybrid of the two. No human has knowingly set eyes on it, although quite a few have been listening to it for over 20 years. And there are many more around the world who may not have heard recordings of its vocalizations, but have heard of them, and who have been inspired to write music, poetry and books about the whale that makes them -- a whale they have dubbed the 'loneliest whale in the world.'

The story begins in the late 1980s, when the U.S. Navy began providing whale researchers with recordings from hydrophone arrays it deployed to listen for submarines in the North Pacific, and which also happened to pick up the haunting moans of baleen whales as they cried out across hundreds of miles of ocean in search of mates.

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In 1989, William Watkins of the Woods Hole Oceanographic Institution began sifting through those recordings and soon noticed something unusual. Whereas most male fin and blue whales vocalize at a range of about 17-18 Hertz, well below the limits of human hearing and ideal for traveling across vast distances underwater, one whale was consistently vocalizing at a much higher range of 52 Hz.

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From 1992, when the Navy made more recordings available, Watkins and his team studied the so-called 52 Hz whale in more detail, triangulating the recordings to track his movements across the North Pacific during mating season. (Outside of mating season, the whales do not generally vocalize.) In 2004, they published a paper in the journal Deep Sea Research, which noted how the whale’s unique vocal properties made it easier to chart its movements.

“It’s very difficult to track a signal consistently in the ocean, without seeing the animal,” explained Mary-Ann Daher, who was part of the team that wrote the paper. “Because if other animals are making sounds at the same frequency, you don’t know if it’s the same guy. But this one, it was the 52 Hz signal that we were able to pick up frequently.”

But that wasn’t the aspect of the research that resonated. What might reasonably have been expected to be a relatively obscure paper in a relatively obscure journal was picked up by media and public alike, who responded to the notion of a whale that was swimming through the ocean, calling out on a frequency no other whale was using, never hearing a response.

The "loneliest whale in the world" was born.

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Watkins had succumbed to cancer by the time the paper was published, and Daher was listed as corresponding author in his stead -- which meant that she was the one who had to deal with the unanticipated flood of media inquiries.

“CNN was on my case, the BBC ... it was horrifying,” she chuckles. “I’m very uncomfortable talking about someone else’s research. I was just a research assistant in that lab. Dr. Watkins ... oh God, he’d be dismayed, to put it mildly, to know of the attention.”

As for the whale itself: “We never had a visual,” Daher says. “We don’t know what species it is. We don’t know if it has a malformation. Obviously, it’s healthy. It’s been alive all these years. Is he alone? I don’t know. People like to imagine this creature just out there swimming by his lonesome, just singing away and nobody’s listening. But I can’t say that.”

That hasn’t prevented others from doing so.

“I get all sorts of emails, some of them very touching -- genuinely," she says. "It just breaks your heart to read some of them -- asking why I can’t go out there and help this animal,” she says. “We as humans, we are very soft-hearted, caring creatures. It’s mostly females who write to me -- not always; I also get males -- but there are a lot of females who identify, feeling they’re not part of a pack. I’m no psychologist but boy, what a fascinating case study.”

It's the human response to the image of a lonely whale, at least as much as the scientific validity of that image, that particularly intrigues documentary maker Joshua Zeman.

“To many scientists out there, the story is kind of annoying,” he concedes. “It over-anthropomorphizes the whale. "Yet ... whales are incredibly social creatures, so how could it not be lonely?"

He first heard the story while writing a screenplay at an artists’ colony, and was immediately struck by his own emotional response to it. Sometime later, after he had returned home, “one of the other colonists wrote to me to say, ‘I’ve written a play about the 52 Hz whale,’ and I thought, ‘Wow, that’s interesting that it affected you so much too,’ and I looked online and saw that there were a lot of people who extrapolated the story of this whale, and created art as a result.”

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Zeman is producing a documentary that looks at why the 52 Hz whale strikes such a chord. It's an emotional resonance that, he suspects, is partly rooted in our unique appreciation of whales.

“Whales are mysterious," he says. "There is always a certain amount of awe about them.”

But Zeman also thinks our responses may say much more about us as a society, about our own growing feelings of disconnection from others as we eschew “real interpersonal face-to-face relationships in favor of 140 character anecdotal relationships.”

But if his documentary focuses on the human response to the 52 Hz whale, it does not ignore the whale itself. Which is why the denouement of the movie will be an attempt to find it.

“I don’t think you can do this story properly without a good old-fashioned quest,” he says. “To not have this exploration and this voyage is really doing a disservice to the story, and to the whale.”

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Leading the scientific team on that expedition will be renowned whale researcher Bruce Mate of the Hatfield Marine Science Center at Oregon State University.

“I don’t believe the animal we’re looking for is a new species, or the dying out of an old species, or anything that dramatic,” Mate explains. “It is much more likely the animal might be the equivalent of an animal with a lisp, that it has -- I won’t call it a speech impediment, because it’s probably understandable to other animals, but it’s different.”

Mate and his team have been continuing to follow the 52 Hz whale, and by combining real-time acoustic monitoring with the whale’s inferred travels since 1992, they will seek to narrow down a search area before setting out to sea at the beginning of the fall mating season next year. They will further refine their search pattern by towing acoustic devices that are tuned specifically to the whale’s unique calls.

“From my standpoint, while I understand that there are some people who are passionate about this whale, who have very strong emotions about the loneliest whale in the world, when we go out and find this animal, I expect to find it in the midst of other whales,” Mate says. “I’m going to guess they’ll be mostly fin whales. My expectation is that we’re going to tag 15 to 20 whales in its vicinity; in the process of getting satellite tag monitors on them, we will also take biopsies, and we will know the genetic pedigree, so to speak, of all the animals we can.”

In other words, whether the team finds the 52 Hz whale, and whether it turns out to indeed be lonely or surrounded by companions, the story will have a happy ending. It will have provided a platform for scientists to learn more about the baleen whales of the North Pacific than they might otherwise have been able to. And while the whale may be lonely, its cries have not gone unheard. And if all goes according to plan, sometime next year, those who have listened to those cries most intently will finally meet up with the whale that makes them.