chapter eight

THOUSAND MILE SONG

Moanin’ in the Deep Sound Channel

 

 

 

 

THREE-FOURTHS OF THE EARTH IS COVERED BY WATER. ALL THE water on the planet occupies a volume of more than three hundred cubic miles, enough liquid to fill a cylinder two miles in diameter that would reach from here to the sun. It’s no place for a human. In the majority of this wet, dense world, it is nearly impossible to see. But sound has amazing power there, especially the lowest, deepest tones of the largest whales, which may be able to travel from one end of an ocean to the other.

Leonardo da Vinci knew that if you were to place a long tube into the water with one end in the waves and the other at your ear, you would be able to hear ships traveling many miles away. That is the earliest European reference to the long-range power of sound in the ocean. As with many of Leonardo’s insights, not much was done with this fact for many hundreds of years. In 1826 Swiss physicist Daniel Colladon stood at one end of Lake Geneva, and Charles Sturm, a French mathematician, stood at the other. At the time, underwater bells were being tested as a way to augment lighthouses to aid in bad weather navigation. Sturm struck a large bell under the water and flashed a light at exactly the same time. The interval between the beacon and the sound was measured at the other end of the lake by Colladon. Since light travels nearly instantaneously, the speed of underwater sound could be calculated. They came up with 1,435 meters per second—nearly five times faster than the speed sound travels in air. (The actual number varies greatly with salinity of water, and its temperature, but they were only three meters per second off from the speed of sound we today know existed in Lake Geneva at that time of year.)

How can sound move more quickly in a denser medium? Light and sound waves are very different animals: light waves are transverse, traveling at an extremely fast speed, vibrating in parallel to the direction they move, like ocean waves crashing against a beach, or rings of latitude on the globe. Light careens through open space, is slowed down by denser liquids, and stopped by solids; we can’t see through a wall.

Sound waves, in contrast, are longitudinal, vibrating straight in the direction they’re moving, like when you shake a Slinky and you watch the pulse move through the coils. When sound waves propel forward, they alternately compress and expand the molecules in the stuff they’re passing through. Turns out that the denser the medium, the faster the molecules shake as the wave goes through it. (It’s even faster in solids—put your ear to the ground and you can hear the buffalo stampeding miles away across the plains or a train far away on its track.)

Cetaceans and humans are after the same things when navigating the deep seas: we’re both trying to find our way in a dark, lightless, foggy world. Although the ancient Phoenicians could figure out how far away a rocky shore was by ringing bells and listening for the echoes, only in the beginning of the twentieth century did we realize this approach might be more effective under water. It was the sinking of the Titanic that inspired us to develop a means to locate underwater objects when they could not be seen. The great ship might never have gone down if they had known that iceberg was coming.

The first successful “echo ranger” was patented in 1914 by Reginald Fessenden of the Submarine Signal Company. His contraption was based on an electric oscillator that sent out a very low-pitched tone, along with a receiver that listened for the echo. It could detect an iceberg two miles away, but it was an imperfect contraption, flawed in an essential way: it was incapable of determining in what direction the huge white deathtrap was hiding.

Underwater sound spreads evenly from its source, making it very difficult to find what we hear. Above the surface, our stereo ears can easily tell where a sound comes from. In water, sound seems to be present all around, like a total reverberating field. The simplest way to tell a noise’s deep sea location is to move, and then listen to whether it gets louder or softer.

The early sound-pinging devices were no use tracking German U-boats in World War I, because the enemy vessels moved too fast. By the onset of World War II, all ships had depth-finders and better echo rangers that could bounce sounds off a hull or pick up the thrum of an enemy propeller from at least a mile away. The whole system was renamed sonar, meaning “Sound Navigation and Ranging.”

In the 1930s scientists began to measure water temperature and pressure and studied how their changing values affect the way submarine sound behaves. Athelstan Spilhaus at MIT invented a contraption called the bathythermograph, shaped like a small torpedo, which recorded both temperature and pressure changes as it was lowered through the water off the side of a ship. Researchers armed with this device learned that the ocean is divided into several distinct layers with different sonic properties. Closest to the surface is a layer warmed by the sun, whose temperature and thickness changes with the seasons, but is at a constant temperature throughout the layer. A sound moving through this layer goes at a reliably constant speed. Next comes the thermocline, a transitional layer where the temperature drops steadily with depth, and as it falls, the speed of sound slows down. Beyond a thousand meters down, the temperature does not vary much more. The greatest influence on speed in the depths is ever-increasing pressure, which causes the sound to travel faster and faster the deeper one gets.

At the end of the 1930s the military discovered that sound moving just between the surface layer and the thermocline tends to bend down toward the layer where the speed slows down. This refraction creates a shadow zone of sonic invisibility, a space where a submarine might be undetectable by enemy sonar. Bathythermographs were standard equipment on World War II submarines. The ships hid stealthily by adjusting their position depending on the changing thickness of the ocean layers.

Sounds produced close to the surface can travel many miles, but they eventually dissipate as the vibrating waves bounce against the surface and diffuse themselves into the surrounding noise. Sound produced thousands of meters down in the ocean might travel very fast, but the pressure is so great that noises rapidly evaporate into the thick liquid silence.

Six to twelve hundred meters down, temperature and the speed of sound are both at their lowest. In this special layer, certain very deep sounds can travel extremely far and still be audible. In the early 1940s, Maurice Ewing at Columbia proposed that low-frequency sound waves, under 100 Hz, which are less prone to scattering and absorption into the material that conducts them, should be able to travel extreme distances. He named this level of ocean depth the “deep sound channel.” Very low-pitched sounds at this depth will reverberate clearly, never touching the surface or the bottom of the sea, and thus travel with little resistance across the oceans of the world. These low sounds become fixed in the deep sound channel and boom and thrum across entire oceans because they do not dissipate and do not reflect or refract off anything. The sound waves vibrate and travel endlessly, losing hardly any power or momentum as they go.

In 1943 Ewing exploded one pound of TNT and soon learned the sound of the blast was picked up clearly by hydrophones two thousand miles away on the coast of West Africa within the hour. Could the sounds of whales also travel this far?

After World War II, the U.S. Navy devoted considerable resources to the new Office of Naval Research. They wanted to track submarines from very far away. In the 1950s the Sound Surveillance System (SOSUS) was launched, a complex array of hydrophones fixed on the ocean bottom and connected to cables that went to secret listening stations set up on coasts all over the world. The Navy was able to hear a lot of things: what kind of submarines were out there, how many propellers they had, whether they were conventional or nuclear, and sometimes even the exact make and model number.

But they also heard a lot of other sounds that were of less interest to them. Deep booms, grunts, howls, screals. Clicks, moans. Monotonously repeating super-low tones that didn’t come from any machine they could find in their secret catalogs. What could be making them?

Eventually, the Navy realized they were hearing whales. They kept this knowledge classified for many years. As far as the Navy was concerned, these sounds were all just “biologicals,” naturally occurring noises of no strategic import. Seamen were trained to identify them so they wouldn’t get alarmed and think that a secret enemy sound was booming across the distant seas. No one outside the Pentagon got to listen to most of these recordings until decades later, when the Soviet Union suddenly collapsed and the Cold War ended.

Once scientists got ahold of these decades of recordings, they heard all sorts of things, which could be located with great precision. Just how precise they can be located is one of the aspects of the technology that remains classified information, but the system is surprisingly accurate for one that must operate in an underwater world known for its opacity. Geologists could locate underwater volcanoes and gain insight into how the ocean floor itself is constantly being created from molten lava pushing up from beneath the Earth’s crust. Biologists finally had a way to track the movements of whales from the changing attributes of their thousand mile songs.

Chris Clark is director of the bioacoustics department of the Cornell Laboratory of Ornithology, the largest such institution in the country. In the bowels of their beautiful new building, a celebration of birds and all things avian, there are a pack of scientists mostly studying whales, on the outskirts of Ithaca a few hundred miles from the nearest sea. In dark rooms they pore over piles of data, endlessly seeking similarities and differences that might bring meaning and purpose to the sounds they have collected over decades in the field.

Clark isn’t exactly sure whose idea it was to open up the SOSUS data to the cetacean research community: “I never asked for it at all. It happened in the spring of 1991, during the first Bush administration. Al Gore, Sam Nunn, and Ted Kennedy pushed through a bill called the Dual Uses Initiative, to take military assets and try to use them for civilian science and environmental purposes. I don’t know where they got that idea.”

Out of the blue Clark received a call from a man at the Office of Naval Research named Dennis Conlon, who asked him to come down to Norfolk and take a look at their data. He hadn’t had much experience with military culture before that. “I was amazed, it was like Dr. Strangelove, the secret war rooms, it was real! I got a message that we would have a special meeting to discuss the Dual Uses, and I saw my name was on the agenda and I suddenly saw I was on the program and had to give a talk about what I would do if I had access to this information. I hadn’t prepared anything, so I got up and told stories.”

And Clark knows how to tell stories. Like many scientists, he has more stories than he has ever had time to write up, stories of analysis but also speculation, ideas he has never had the chance to follow up on because he’s too busy raising money to keep his lab afloat. When Clark speaks, he reveals a side of his experience that doesn’t appear in his scientific writings. Here is a man who truly enjoys imagining what it must be like to be a whale:

“From a bowhead’s point of view, migrating under the spring pack ice in the Arctic, vision is reduced down to several hundred feet, and hearing is everything.” Bowhead whales are the only whales besides humpbacks who sing songs, a simpler song than the humpback but a song nonetheless. “It sounds as if someone is bowing a cello. Hreeaph, hmmmmr. Hreeeaph, hmmmmr. And you listen to this and you think that maybe you’re hearing the ice grinding in the background, because they’ve incorporated these sounds of ice into their song! It’s not that surprising, because the ice has forty different voices, it can sound like a freight train, like wolves howling, like babies crying. So there’s this continuum of sounds from natural physical forces such as the ice growing and stretching, all the way to the animals who are traveling through this area, this very complex underwater world beneath the ice.”

He explains his theory that the traveling whales gather themselves together solely through listening. “Communication by sound is the means by which your comrades—excuse the term, admiral—in front of you and behind and beside you, negotiate their way through the icefield. You’ll hear hmmmm and then ten or twenty seconds later mmmmmmh and then a few minutes, then another, with space in between. We’re all connected by sound.”

Clark calls such a group of traveling whales an “acoustic herd,” a group of animals that holds itself together with sound. Their music, like work songs or spirituals, keeps the culture going: “Imagine what it must be like to be a bowhead in twenty-four hours of darkness, working my way through an ice field where the folklore of my culture has told me that my grandfather has been trapped and nearly died in the process. This is not like migrating across the open sea, this is frozen ocean, under the ice, by bouncing their sounds off the ice, the whales may reconstruct an image of their underwater world.”

He asked the audience to partake in a thought experiment: “Close your eyes and remember what’s around you, and you create a picture based on your eyes. Now if I told you to close your eyes and tell me a picture based on what you hear, not on what you see, you’d find it very difficult. But that is what I think these animals are doing.”

The Navy was impressed. A couple of weeks later, Clark was called down to Washington and named chief marine mammal scientist for the Dual Uses Initiative. “I told them, ‘wait a minute, you guys already know all this stuff. You produced cassettes to train Navy guys who distinguish a ‘biological’ from a submarine, different guides for each ocean. In every training manual that I’ve found for Navy technicians, every image I’ve seen, every spectrogram, in the background there were always whales! They had terminology for things like the ‘jezz monster,’ when all the fin whale voices come to a crescendo during the summer months, and they just tried to block that stuff out. It was a pain in the ass to them, because it made the subs harder to spot.”

On his first visit to SOSUS headquarters in 1992, Clark was ushered into a dark room the size of a gym with row after row of dot matrix printers spewing out scrolls covered with dashes and dots, old-fashioned representations of the sounds picked up by each of the hydrophones stationed all over the world’s oceans. Clark peered to study one printout, and he saw a familiar blip near the bottom of the scale, “exactly the right sound frequency for a blue whale. Then as I walked along the rows of machines, comparing the patterns from separate arrays miles apart on the ocean bottom, I noticed something else: they were detecting the same whale!” He felt a chill on the back of his neck as he realized that the Navy’s system could be used to locate whales singing across an entire ocean: day by day, hour by hour.

Blue whales, the largest animals that have ever lived, have ten times as many neurons as we do, devoted entirely to picking up sounds below 100 Hz, way beneath the lowest notes of the piano. We can barely hear what they are doing. A blue will make one long, dark moan, lasting up to half a minute, and then wait exactly seventy seconds and make the same sound. Over and over again, in an exact but very slow rhythm, for days. In the Indian Ocean, they do it every 140 seconds.

Fin whales make a simpler sound, an extremely low pulse of 20 Hz repeated every thirty seconds or so, beneath the lower limit of human hearing. Because of the simple and regular nature of the fin whale’s beat, it has been easiest to use in testing the theory of the thousand mile song. When this sound was first heard during the Cold War, some thought it was some secret frequency being used by the Russians to fill the oceans with standing waves that could allow the enemy to detect the position of our submarines. Ocean acoustics textbooks in the 1960s were still skeptical that such tones could be of animal origin. Suddenly the Navy started paying more attention to low regular pulses. Turned out these sounds were being made by the long, sleek Ferraris of the whale world, the fin whales. The sounds are so far apart from one another, we can only grasp their rhythm when they are sped up thirty times. Figure 32 shows a comparison of the tonal sounds made by some of the larger whales and by human beings. Click sounds reach much higher frequencies than these:

FIG. 32. COMPARATIVE RANGE OF TONAL SOUNDS MADE BY HUMANS AND VARIOUS KINDS OF WHALES.

And figure 33 shows how well whales and humans hear frequencies along the spectrum. The lower the threshold, the easier it is for each animal to hear that particular frequency:

FIG. 33. HOW WELL HUMANS AND WHALES HEAR DIFFERENT FREQUENCIES. THE LOWER THE THRESHOLD, THE EASIER IT IS FOR THE ANIMAL TO HEAR.

As early as the 1970s Roger Payne hypothesized that these largest whales who make the lowest sounds could conceivably communicate across entire oceans, because of the aforementioned properties of the deep sound channel, shown in figure 34 at right.

Over the coming decades it was determined that only the male blues and fins were making the regular low sounds. Since no one had ever found breeding grounds for fin or blue whales (whalers had sought such a gold mine for centuries), scientists began to suppose that such a place was not needed. Perhaps as the male whales called out for mates across an area of thousands of miles, the females who heard would then head toward the source of the sound.

Do they actually do it? So far there is only anecdotal evidence that whales themselves listen to songs from thousands of miles away. Serge Masse, a Montreal-based developer of cetacean research software (his latest creation is Leafy Seadragon, a program designed for two-way dolphin/human communication), remembers a Navy sonar man he knew who tracked fin whale booms in the seventies. Loud ones were detected right near his submarine, off Stellwagen Bank near Cape Cod, but there were very faint echoes that couldn’t be placed. On the phone with colleagues near Spain, he got confirmation that whales off the European coast were making similar subsonic booms just an hour before. Why wasn’t this published? “The information remained classified for decades,” Masse smiles. “But now it can be told.”

FIG. 34. A LOW-FREQUENCY PULSE PRODUCED BY A FIN WHALE COULD BE HEARD BY ANOTHER FIN WHALE ON THE OTHER SIDE OF THE ATLANTIC WITHIN THE HOUR.

Scientists, though, have certainly heard baleen whale sounds from great distances away. With access to the Navy’s super-accurate equipment, Chris Clark was able to track a blue whale for forty-three days from a thousand miles away. This giant blue whale sang continuously day and night. He began five hundred miles northeast of Bermuda swimming on a steady south-southwest course for three days. He passed just south of an undersea mountain and then turned toward the west and swam until he was two hundred miles northeast of Cuba. Then he turned right and ended up about a hundred miles from where he began. There he fell silent. Altogether this whale traveled twenty-two hundred miles over the course of a month and thirteen days.

Clark believes the whale may have echo-ranged off the seamount and then off Bermuda as a means of navigation. Even such deep sounds could be used for echolocation, especially if they are sung with such rhythmic precision, by an animal hip to long, drawn-out scales of time. Blue whale sounds at their source are 180 dB, as loud in water as a jet engine is in air. You wouldn’t want to be listening too close to one. We would likely feel a huge rumble throughout our bodies if we swam nearby.

What is this long simple song then? A mating ritual, or a slow-mo sonar form? Clark has shown that the mathematics for deep booming sonar could work, but there is no data to support that this is what is actually going on. But the thousand mile song takes hold of our imagination right away: “I could show you the evidence today. I can listen in Puerto Rico to a whale way up on the Grand Banks. Can the whales do that? You might well ask, ‘What would they have to say?’ Then you’re suddenly putting on this silly human restriction. A whale might turn around and say to me, ‘What would you possibly have to say to one another sitting just two meters apart?’”

Like so many great scientists, Clark is not afraid to be a bit of a dreamer. He is more concerned with saving the whales from increasing threats of noise and pollution than he is in figuring out what they’re up to. More than once he has sought out the advice of musicologists: “Marty Hatch, a specialist in Indonesian gamelan here at Cornell, had this to say to me, ‘You know Chris, you look at all this singing as data, but I think of it as a musical, emotional experience.’ Musicians hear song, and this is where I sometimes lean away from the scientific and tend to agree with them. Why can’t we just appreciate it as a phenomenon that is phenomenal?”

No human musician could stay in time counting as slowly as these whales do. These incredibly low thumps and moans are rhythms at so lax a pace that they are barely perceivable by human beings. Speed a blue whale song up ten times, and thirty minutes becomes three. Move the pitch up to the realm of a cello, bowhead, or a human moan and exactly every three seconds comes the same soft moan. Only at this slow sense of time do we hear the thousand mile song, a great sigh in the deep sound channel, echoing from one end of an ocean to another.

Is it right to call such a single repeating phrase a song? We call animal sounds “songs” for several different reasons. One, if we imagine a male is serenading a female, this begins to sound like music to human scientists. Two, if the patterns have musical qualities: rhythm, pitch, shape, and form. Three—and this to me is the most interesting and often overlooked reason—if the form of the sound does not affect the message conveyed, if there is no meaning to be explained apart from the singing, then we have a kind of communication that works like art, not language.

In 2007 several papers were published that shed new light on the deep dark sound world of the blue whale. Erin Oleson, with Sean Wiggins and John Hildebrand, discovered that blue whales off Southern California actually make three kinds of sounds, A, B, and D. The A and B sounds are quite consistent, sometimes heard separately, but more often combined into AB AB AB sequences, and these comprise what is usually called the “song” of the blue whale. The D sounds, in contrast, are very deep and variable downsweeps, as shown in figure 35. A and B sounds are generally made by males while they are on the move. D sounds are made by males and females, often when they are feeding. In bird terminology, we might label them “calls.”

FIG. 35. THE A, B, AND D SOUNDS OF BLUE WHALES.

Using suction-cup tags attached to the giant whales, for the first time scientists were able to measure how deep the blues were while singing their ultra-low tones. Surprisingly, most of the songs were made at a fairly shallow depth. Figure 36 shows the behavior of one tagged male blue whale, diving deep and coming to the surface repeatedly. Note the shallow depth at which he made separated A and B sounds, and how he makes the transition to the AB AB AB song pattern, over a period of five hours.

FIG. 36. THE RISING AND FALLING, SINGING AND STOPPING BEHAVIOR OF ONE BLUE WHALE.

He begins by milling about with another blue whale, whose sex is not mentioned. As he goes off on his own, our boy starts to travel northwest at four knots, making isolated A and B calls along the way. After two hours, he combines them and a song is born. Who is listening? We don’t know. How far can it travel? Maybe twenty to fifty miles, nothing like the thousand miles Clark and Payne believe to be possible. Further studies of tagged whales will be needed to show if the dream of distance is science or myth.

Another 2007 publication, by Mark McDonald, Sarah Resnick, and the director of the lab, John Hildebrand, is the first to identify clear regional differences in the song of the blue whale. Their paper argues that the songs are distinct enough to identify clear, music-defined populations of blue whales that are distinguishable by geographically defined dialects. Certain sounds in the song are sometimes blurred together, sometimes separated by a pause, but the same syntax always appears, unique to each part of an ocean. The authors point out that the song is much easier to depict in sonograms than it is to perceive by human ears, even if sped up and transposed to a higher octave. Even though each of the low moans takes several minutes to sing, the structure is far less complex than humpback song, so the distinct dialects are easier to see in figure 37 on the preceding page.

FIG. 37. BLUE WHALE DIALECTS AROUND THE WORLD.

The differences are subtle, but important, because they enable researchers to identify distinct populations of blue whales around the world. Traditionally, separate populations of blue whales were distinguished within arbitrary International Whaling Commission boundaries, for the purpose of monitoring their number and the autonomous health of each group. But this paper suggests that the different populations now be reclassified along acoustic lines, kind of like giant acoustic clans of the kind Whitehead and Rendell identified for sperm whales. Except blue whales seem to congregate in geographically distinct acoustic clans, their movements differing from group to group, as shown in figure 38.

FIG. 38. WHERE THE BLUE WHALES ARE.

Blue whales keep a rhythm too slow for any human to detect. And they may be getting even deeper. John Hildebrand has noticed that blue whale sounds are getting lower, going down an average of a tenth of a hertz each year. He believes this is because their numbers are increasing, and they need to communicate ever farther, and the lower the sound, the better it will travel. So far this remains an unpublished hypothesis. The largest animal that has ever lived on Earth makes a deep music whose subtle variations we are just starting to discover.

The ocean is by no means an opaque, silent world. It has always been naturally full of noise, at many frequencies. Wind and waves keep the sea rumbling at frequencies 500 Hz and above. Seismic explosions and earthquakes create sudden booms at the lowest end of the scale. In the tens of thousands of hertz and up to the hundreds, where dolphins squeak and hear, they have to reckon with the sound of the molecular agitation of water itself. Rain sends its high white-noise rush down beneath the surface. The underwater turbulence of the whole sea makes its presence felt at many frequencies.

But apart from the occasional underwater eruption, the bottom of the scale is remarkably free of sonic interruption. This fact, combined with the physics that allows very low pulses to travel so very far, may explain why these largest whales have evolved an ability to sing and to listen deep down in these frequencies. The deep sound channel, which allows 20 Hz sounds to lose just 1 dB in energy over two thousand miles, makes these tones the perfect pitches to send across great undersea distances.

Yet it is a much different sound world once human activity is brought into the mix. Today there are thousands of large ships coursing through global waters, most of them with big propellers making deep motor noises that peak around 90 dB in the frequencies between 20 and 70 Hz. This human-made sound is so ubiquitous in today’s oceans at these very bottom frequencies that the long-range singing potential of these greatest whales is seriously compromised today.

Before propeller ships were trafficking all over the world’s oceans, fin-whale pulses could easily travel a hundred and fifty miles at the surface and four thousand miles in the deep sound channel. With current levels of shipping noise, they are audible just fifty miles away at the surface, or six hundred miles deep down, before their volume is drowned out by background propeller rumble.

How much of a difference does this make to the whales? Birds in cities can handle the din; we’ve recently learned that they adapt by making louder sounds. In the acoustic space of the deep sound channel, can whales turn up to eleven? They could only hear a potential mate from a thousand miles away if the ocean were supremely quiet, and across most of the planet, that is not the case. Should we do something about this? Could we make our ships quieter for the sake of the great whales? Our noisy human world has changed the lives of whales forever.

Sudden human sound events in the ocean are much easier to stop. In March of 2000, whale researcher Ken Balcomb was astonished to find a Cuvier’s beaked whale stuck in the shallows near his home in the Bahamas. Beaked whales are among the least known of cetaceans, since they usually live too deep in the water for us to see them often enough to learn much about them. Here he was, one of the world’s experts on the beaked whale, face to face with one who was going to die unless he did something about it. It took more than an hour for Balcomb and his colleagues to coax this twenty-foot-long three-ton whale away from the beach and back into safer waters. The whole time the beast seemed confused and disoriented, but eventually he went on his way.

That was only the beginning. Soon afterward, Balcomb received a call that five beaked whales had been stranded on nearby beaches and most were still alive. By the end of the day, fifteen beaked whales were writhing on Bahamas beaches, along with two even bigger Minke whales. By the end of the day six of the beaked whales died. What happened? The U.S. Navy had been conducting a mid-frequency sonar exercise, bombarding the channel with reverberations around three thousand Hz, to a level of 150 dB, every twelve seconds, for sixteen hours.

Subsequent autopsies found that the whales had died not so much because of hearing loss, but because they had developed a kind of decompression sickness (a version of the bends), because the particular frequency used by the Navy matches the resonance frequency in the air space inside their heads. Balcomb describes it as follows: “Envision a football squeezed to the size of a ping-pong ball by air pressure alone. Now envision this ball compressing and decompressing hundreds of times per second, between your two ears. This is what the Cuvier’s beaked whales experienced as a result of the Navy’s sonar testing in March 2000. Airspace resonance phenomena resulted in hemorrhaging, which caused the stranding and deaths in the Bahamas.”

Although at first they were reluctant to admit complicity in the deaths of these little-known whale species, eventually the Navy did accept blame for the whale strandings. In theory they have agreed after years of negotiation to refrain from testing mid-frequency sonar in areas where whales are known to be present; however, in practice these sounds could travel up to a hundred miles and still have enough energy to harm whales. Sonar testing has been linked to whale deaths in about thirty instances over the last forty years; more than a hundred whales have died. The Navy defends itself by saying that this number pales beside the amount caught in fishing nets or cumulatively harmed by pollution, but sonar testing is much easier to do something about than these more widespread threats.

In early 2006 the U.S. Marine Mammals Commission released a report on acoustic impacts that included contributions from all the major stakeholders in this debate: an environmental caucus, a scientific caucus, an energy industry caucus, a shipping caucus, and a federal caucus. It is a fine case study of how an issue can look completely different depending where you’re coming from. The environmentalists said if there’s even a chance that an underwater sound might harm a whale, we shouldn’t make that sound. This is the famous precautionary principle—what might be bad could be bad; do nothing unless it’s absolutely necessary. The energy industry emphasized its need to fire underwater air guns and unleash explosions for seismic exploration, because of course we need the energy, and of course they need the money. Scientists said we simply don’t know enough to be sure about the impacts, so we must do more research. They suggested that we really should study the continuous impact of moderate noise more fully, but they did not suggest how this should be done. The shipping industry agreed in principle to investigate reducing propeller noise, especially if the change could be legislated gradually, and if convincing proof were provided that general shipping noise was a problem for whales.

Since this report presented so many different viewpoints on the same problem, the committee was unable to reach a consensus. In the summer of 2006, the Navy was preparing to conduct exercises in the Pacific that involved mid-frequency sonar, the kind known to harm beaked whales. They had already agreed to certain restrictions on the tests: no active sonar in deep canyons where beaked whales might be hanging out, and sonar pinging would be turned off whenever there was a possibility of whales in the vicinity. There was still protest from environmental groups, but the Navy insisted the tests were essential: “We need to track the submarines of our possible enemies, nations like Iran, North Korea, or China.”

The Natural Resources Defense Council immediately sued the Navy with a cease-and-desist order, and a judge in the Los Angeles District Court agreed that going through with the tests would violate the National Environmental Policy Act. The Navy agreed to alter the testing site somewhat, pledging to steer clear of the recently decreed Northwestern Hawaiian Islands Marine National Monument, instructing all personnel to be especially alert for whale sounds. No longer were these voices mere “biologicals.” They would now be an important part of a sonar operator’s listening field. Environmental lawyer Richard Kendall called the settlement “a significant step forward in the protection of our oceans,” while an admiral called it “a small number of additional mitigation measures.”

It looked like a rosy compromise until January 2007, when the Navy suddenly claimed an “exemption” from the Marine Mammal Protection Act and gave itself permission to conduct whatever tests it wants for the next two years, citing national security as their justification. So much for the image of a rare whale helpless on the beach, pulverized by resonating tones inside its air sacs, all the result of secret tests of a technology designed to flummox enemies we’re not even sure exist.

The Navy still finances much of the research on whales and dolphins. They did turn their classified underwater expertise over to those scientists who could best appreciate it. They remain an ambiguous influence on our quest to understand the sonic abilities of cetaceans. They do not feel the issue is resolved and are still seeking advice on how to remedy the situation. Rumor has it they’ve even asked the endlessly creative Jim Nollman for assistance on this problem.

The rise of chronic human noise in the oceans remains a more worrying threat to whales, because it is much harder to control than the occasional sonic blast. As Peter Tyack describes it, “The deepest whale songs used to carry for hundreds of kilometers. Now it turns out that the thing that dominates the frequency range down there is shipping noise. This is where we put the most acoustic energy in the ocean. If that increased low-frequency din is preventing a male and female from finding each other, it is important. It’s not as visible as a dead whale on the beach, but it might be much more prevalent.”

A recent study shows that North Atlantic right whales, of which only three hundred remain, have started making higher-pitched calls over the last half century. This change may be a response to a habitat full of more big propeller ships than ever before. Each decade the hum of motors adds nearly 10 dB of rumbling sound to the background noise the whales have to reckon with.

We can’t be sure of the precise effects of chronic loud human noise on the whales, and this uncertainty is capitalized upon by those whose activities would be hampered by having yet one more problem to worry about: seismic explorers looking for oil, the Navy testing new equipment. Their position remains, “If we’re not sure it will harm the animals, why worry?” Environmentalists and whale lovers favor the precautionary principle, where what we don’t know can still hurt us, quite a bit. Better to be careful, and show greater respect for these great singers of the seas.

I tend to agree with Jim Cummings, founder of the Acoustic Ecology Institute, a clearinghouse of information on all sonic assaults on our environment. After carefully reviewing this issue for many years, this is what he has to say: “There are other foundations to stand upon in creating public policy than those built of scientific certainty. We need to remember that the effects of our actions tend to ripple and interact in ways that we cannot predict, or often even fully recognize. This is surely the case with making extreme noise in the sea.”

Science must praise uncertainty, as it progresses by constantly scrutinizing itself and questioning assumptions, scrupulously amassing ever more data. When it comes to the world of whales and the remote deep sea, its conclusions are understandably incomplete. Based on its own criteria for objectivity, science can rarely tell us exactly what to do. So we should not be misled into thinking that our care and feeling for whales and their world is something subjective, emotional, and easy to discount when it comes to planning their future. Our species has no future on this planet until we consider the flourishing of all other forms of life as part and parcel of human progress. There is a gentler, more humane way to live along with the sea. We must learn to hear the ocean’s music, so as not to play our human part too loudly.