By William Broad, The New York Times, December 10, 2012
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| A rare and endangered blue whale offshore near Long Beach, Calif. |
When a hurricane
forced the Nautilus to dive in Jules Verne’s “Twenty Thousand Leagues Under the
Sea,” Captain Nemo took the submarine down to a depth of 25 fathoms, or 150
feet. There, to the amazement of the novel’s protagonist, Prof. Pierre Aronnax,
no whisper of the howling turmoil could be heard.
“What quiet, what
silence, what peace!” he exclaimed.
That was 1870.
Today — to the dismay of whale lovers and friends of marine mammals,
if not divers and submarine captains — the ocean depths have become a noisy
place.
The causes are human: the sonar blasts of military exercises, the
booms from air guns used in oil and gas exploration, and the whine from
fleets of commercial ships that relentlessly crisscross the global seas. Nature
has its own undersea noises. But the new ones are loud and ubiquitous.
Marine experts say the rising clamor is particularly dangerous to
whales, which depend on their acute hearing to locate food and one another.
To fight the din, the federal government is completing the first phase
of what could become one of the world’s largest efforts to curb the noise
pollution and return the sprawling ecosystem to a quieter state.
The project, by the National Oceanic and Atmospheric Administration,
seeks to document human-made noises in the ocean and transform the results into
the world’s first large sound maps. The ocean visualizations use bright colors
to symbolize the sounds radiating out through the oceanic depths, frequently
over distances of hundreds of miles.
It is no small ambition: the sea covers more than 70 percent of the
planet’s surface. But scores of the ocean visualizations have now been made
public.
Several of the larger maps present the sound data in annual averages —
demonstrating how ages in which humans made virtually no contribution to ocean
noise are giving way to civilization’s roar.
The project’s goal is to better understand the cacophony’s nature and
its impact on sea mammals as a way to build the case for reductions.
“It’s a first step,” Leila T. Hatch, a marine biologist and one of the
project’s two directors, said of the sound maps. “No one’s ever done it on this
scale.”
The began the effort in 2010 at the behest of Jane Lubchenco, a
prominent marine biologist who is the first woman to head the agency. Dr. Hatch
and her colleagues assembled a team of sound experts, including HLS Research, a
consulting firm in La Jolla, Calif. This summer, they unveiled their
results on the Web, as did a separate team of specialists that
sought to map the whereabouts of populations of whales, dolphins and porpoises.
Michael Jasny, a senior policy analyst with the Natural Resources
Defense Council, a private group in New York that has sued the Navy to reduce
sounds that can harm marine mammals, praised the maps as “magnificent” and
their depictions of sound pollution as “incredibly disturbing.”
“We’ve been blind to it,” Mr. Jasny said in an interview. “The maps
are enabling scientists, regulators and the public to visualize the problem.
Once you see the pictures, the serious risk that ocean noise poses to the very
fabric of marine life becomes impossible to ignore.”
Legal experts say the new findings are likely to accelerate efforts
both domestically and internationally to deal with the complicated problem
through laws, regulations, treaties and voluntary noise reductions.
The government already has some authority to regulate oceanic sound in
United States waters through the Endangered Species Act and the Marine Mammal
Protection Act, though exemptions to these laws exist for the military.
The International Maritime Organization, a United Nations body
responsible for improving marine safety and reducing ship pollution, also has
the authority to set acoustic standards. In the past few years, encouraged by
the United States, it began discussing how to achieve voluntary noise
reductions.
Since many commercial vessels are registered abroad, and most shipping
noises arise in international waters, the organization’s backing is seen as
crucial for reductions to be substantial enough to have global repercussions.
“Right now we’re talking about nonbinding guidelines,” said Michael
Bahtiarian, an adviser to the United States delegation to the maritime
organization and a senior official at Noise Control Engineering, a company
outside Boston that specializes in reducing ship noise and vibrations. “At a
minimum, the goal is to stop the increases.”
The oceanic roar originates because of the remarkable — and highly
selective — way in which different kinds of waves propagate through seawater.
While sunlight can penetrate no more than a few hundred feet, sound waves can
travel for hundreds of miles before diminishing to nothingness.
Sea mammals evolved sharp hearing to take advantage of sound’s reach
and to compensate for poor visibility. The heads of whales and dolphins are
mazes of resonant chambers and acoustic lenses that give the animals not only
extraordinary hearing but complex voices they use to communicate.
In recent decades, humans have added raucous clatter to the primal
chorus. Mr. Bahtiarian noted that the noise of a typical cargo vessel could
rival that of a jet. Even louder, he added, are air guns fired near the surface
from ships used in oil and gas exploration. Their waves radiate downward and
penetrate deep into the seabed, helping oil companies locate hidden pockets of
hydrocarbons.
Marine biologists have linked the human noises to reductions in
mammalian vocalization, which suggests declines in foraging and breeding.
Worse, the Navy estimates that blasts from its sonars — used in
training and to hunt enemy submarines — result in permanent hearing losses for
hundreds of sea mammals every year and temporary losses for thousands. All told,
annually the injured animals number more than a quarter million.
The federal sound study examined all these noises but zeroed in on
commercial shipping because it represented a continuous threat, in contrast to
sporadic booms. For North Atlantic shipping, the project drew up more than two
dozen maps. All their scales went from red (115 decibels at the top) to orange
and yellow, and then to green and blue (40 decibels at the bottom). The maps
presented the results in terms of annual averages rather than peaks.
A decibel is a measure of noise, and peak levels underwater can be
incredibly loud. When monitored by a hydrophone at a distance of one meter
(about three feet), a seismic gun produces 250 decibels, an oil tanker 200
decibels and a tugboat 170 decibels, according to Mr. Bahtiarian.
To draw up its annual maps, the sound project used computers to
average out such peaks over time, as well as to slowly diminish the noises as
they traveled over the ocean’s vast reaches. The study also chose to model the
low frequencies used by sea mammals for hearing and vocalization, and tracked
how far the sounds penetrated.
Maps of the North Atlantic show mostly oranges in the upper waters,
but many blues appear as the readings go downward as deep as one kilometer, or
six-tenths of a mile. At that depth, the sound maps clearly show the ability of
the Mid-Atlantic Ridge — a mountain chain that runs down the ocean’s middle —
to diminish the radiating noises by breaking up patterns of sound waves.
Dr. Hatch, of the sound study, said too many areas of the ocean
surface (where sea mammals and whales spend most of their time) are orange in
coloration, denoting high average levels.
“It’s like downtown Manhattan during the day, only not taking into
account the ambulances and the sirens,” she said. “I’d be happier saying it was
like a national park.”
Vessels for fishing and research, including new ships being built for
N.O.A.A., are already being quieted around the world. The trend derives not so
much out of concern for sea mammals but from the realization by oceanographers
that quiet ships let them do better science.
Marine engineers say the mechanics of ship quieting are relatively
straightforward if applied in the design stage. The biggest factor is the
ship’s propeller, which has to be shaped exactly right to lessen cavitation.
The noise arises when the force of a propeller cutting through
seawater results in millions of voids and bubbles, which then collapse
violently. Experts say quiet propellers have a benefit beyond helping sea
mammals in that some kinds can reduce fuel consumption.
Other measures for quieting include adding layers of sound-absorbing
tiles to the walls of noisy rooms as well as mounting engines, pumps, air
compressors, and other types of reciprocating machinery on vibration isolators.
Mr. Bahtiarian of Noise Control Engineering, who has written extensively on the
topic in professional journals and for expert committees, noted that a parallel
to ship quieting had been under way in the airline industry for decades. City
officials and airport neighbors, as well as federal officials, have prodded the
manufacturers of jet engines to find ways of reducing noise.
Experts note that the magnitude of the problem on land and sea is
similar, in that the global fleets of commercial jets and ships both number in
the tens of thousands. But designing better ships to quiet the ocean, Mr.
Bahtiarian said, will take longer.
“A ship’s lifetime is 30 or even 50 years,” he noted, “so it could be
a lot longer” before improved designs start transforming the fleet.
Still, Mr. Bahtiarian added, the quieting trend seems inevitable given
the new reports about sound pollution and rising awareness about the dangers to
whales, dolphins and other sea mammals.
“The technology is there,” he said. “It seems like it’s just a matter
of time.”
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