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101
LEARN
MORE
Dig into the sound
library, and read
more at
www.OCR.org.
There was a time,
not that long ago,
when whales could
sing to each other
across oceans.
Cetaceans evolved
in a world of sound.
They, like us, are
highly adaptable
creatures — able
to revel in the bow
waves of the very
machines that are
polluting their
acoustic environ-
ment. Yet I wonder
if their ability to
find joy in the face
of adversity will
be enough to save
them, and I wonder
how well we
humans would
fare if somebody
suddenly turned out
the lights.
— Bob Talbot
whales chatter and pulse together across
large expanses of open ocean. Even the whis-
tling of barnacles carries some critical bio-
logical message that we may never decipher.
We know larval forms of reef animals
imprint on the sounds of their “mother
reef.” When they are first conceived these
tiny organisms are not served by remain-
ing in their birth habitats, in which mil-
lions of mouths are seeking food. So in the
early stages of life they disperse out into
the pelagic zone to gain some heft. But
once they are large enough (and often in a
completely different shape than their larval
form) they need to return to the reef to live.
They find home by following the sounds
they know from the first stages of their life.
We know they do this, but we don’t know
how they imprint. In many cases we don’t
even know how they hear.
Sound WaveS underWater
Terrestrial vertebrates (mammals, amphib-
ians, reptiles and birds) sense pressure gra-
dients in air using diaphragms (ear drums)
attached to the middle and inner ears. This
is a very sensitive system, but as any diver
knows it is poorly adapted to the extreme
pressure gradients found underwater.
Marine animals use different kinds of
acoustical sensing systems including swim
bladders, acoustical lipids, various hair-
cell systems and bone accelerometers that
sense pressure change as well as particle
motion in the water.
Sound works differently in water than in
air. Water is much denser and is not com-
pressible. This allows for a more efficient
transfer of acoustical energy through water
than through air. It is fairly easy to make
a sound in water that can be heard a few
thousand miles away; baleen whales do this
all the time. Humans also do this all the time
in water, but unlike whales that use these
sounds for biological purposes, we do it for
commercial, industrial and military purposes
— often to the detriment of the sea animals.
a GroWinG CaCophony
The ocean is 10 times louder today than
it was just 50 years ago. Transoceanic
commerce is a major cause; some 95,000
merchant ships ply the seas with large
cavitating propellers and throbbing
engines that can be heard throughout the
ocean. As 7 billion humans become ever
more dependent on fossil fuel, the noise
of deepwater seismic-exploration ships
towing arrays of air guns can increasingly
be heard blasting away every 10 to 15
seconds, hour after hour, day in and day
out for months at a time. As deepwater
fossil fuel is discovered and exploited, the
sounds of seafloor-mounted wellheads
and processing equipment screech and
hum across vast tracts of the ocean bot-
tom. Navies have their own repertoire of
noises including low- and mid-frequency
sonars, the noise of their ships and occa-
sional explosions from torpedoes, mines
and projectiles.
Humans are a noisy species, and this is
nowhere more evident than in the ocean.
The impacts are becoming more appar-
ent in the form of catastrophic marine-
mammal strandings, compromised and
depleted fisheries and high stress levels
in animals that can lead to biological dys-
function. Because we know so little about
how sea animals hear and what they do
with sound, we have a very limited under-
standing of the impact of our noise.
In some cases the sounds we make might
not be such a problem; the ocean with its
crashing waves, grinding ice, pounding
rains and billowing hydrothermal vents can
be a noisy place, and animals have adapted
and evolved to account for these sounds
over the millennia. But the sounds we bring
into the sea are quite different from these
naturally occurring noises. Thus, we must
learn how the din of our ocean enterprises
affects the sea’s inhabitants, or we risk
creating an environment in which their
survival is uncertain.
AD
As coastal and deepwater
ocean areas open up to
fossil-fuel, wind and
tidal-energy development,
biologically disruptive
noise is a potential
consequence. Attend
public hearings about
these proposed projects
to find out if and how
this issue is addressed.
BOB T A L BO T