el color del canto de las ballenas

August 1, 2006

Subtle Math Turns Songs of Whales Into Kaleidoscopic Images
By GRETCHEN CUDA
(Del nytimes)

What do whale songs and wavelets have in common? Quite a bit, and the wavelets have nothing to do with water.

In a Northern California studio, Mark Fischer, an engineer by training, uses wavelets — a technique for processing digital signals — to transform the haunting calls of ocean mammals into movies that visually represent the songs and still images that look like electronic mandalas. (His art can be found at aguasonic.com.)

Mr. Fischer learned about acoustics by developing software for Navy sonar and the telecommunications industry. Years later, a serendipitous brush with whale researchers in Baja California led him to take a closer look at whales and the diversity of their intricate underwater communication. “I don’t think anyone has ever spent even a little time around a whale and not been amazed by it,” Mr. Fischer said in an interview.

Mr. Fischer creates visual art from sound using wavelets. Once relatively obscure, wavelets are being used in applications as diverse as JPEG image compression, high definition television and earthquake research, said Gilbert Strang, a math professor at the Massachusetts Institute of Technology and an expert on wavelets.

They are popular now in part because they can capture intricate detail without losing the bigger picture, and when presented in circular form (using a cylindrical coordinate system), repeated patterns are even more evident. By stringing successive images together, Mr. Fischer transforms still images into animated audio files that bring the sound to life.

Among whales, certain sounds and patterns are unique to different species, and even individuals in a group — something like an auditory fingerprint, Mr. Fischer said. “To anyone who doesn’t listen to it on a regular basis it sounds like a bunch of clicks,” he said. “But if you’re a whale — or someone who studies whales — it becomes clear that they have their own dialects.”

Wavelets are capable of picking up those distinctions, Mr. Fischer said, nuances that may be missed by the human ear or less detailed visualization methods. “You can pick out any one of those movies and I’ll tell you what it is without hearing a thing,” he said. “The differences are that dramatic.” He envisions a day when researchers may be able to use images generated using wavelets to identify and track individual whales.

Peter Tyack agrees that the technique has potential not only as art, but as a scientific research tool. A senior scientist at Woods Hole Oceanographic Institution, Dr. Tyack studies the way humpback whales communicate, trying to show that the repetitions in whale songs follow grammatical rules similar to those of human language.

“Looking at those figures, it looked like you could see a lot of repeated units,” Dr. Tyack said of the images. “It looks like he’s visualizing some of the points that we made in the paper about humpback song.”

Despite having analyzed recordings from at least 16 species of whales, Mr. Fischer said he had just scratched the surface. “It’s still a wide-open world out there,” he said. “You think you’re in the 21st century and we have the means to get anything, but when it concerns the deep ocean there is still quite a bit of mystery.”

In the meantime, Mr. Fischer hopes that by merging science and art, he will inspire a greater appreciation of whales among both marine biologists and the public, as he gives many people a glimpse of a world they would otherwise never experience.

“It’s a very rare opportunity to be in the water listening to a whale,” he said. A picture, on the other hand, is something you can hang on your wall and look at every day.

“When you see what whales are doing with sound, or begin to see what they are capable of, it is clear that humans are not the only artists on the planet,” he said.