Momo An
Anni Eloyan
Heather Wright
Geology 12 #7341
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The two scientists that lead to the discovery of the SOFAR
channel are Maurice Ewing and J.Lamar Worzel. They
conducted research on acoustics in the ocean that helped the
navy detect enemy submarines or mines, and also helped the
U.S to avoid detection.
Also the SOFAR Channel was known as the “deep sound
channel” which was discovered by Russian expert in acoustics
Leonid Brekhovskikh.
However, Ewing and Worzel predicted in their discovery, that
low frequency sound waves are able to travel greater
distances than higher frequency waves, due to the fact that
lower frequencies are less likely to be scattered and absorbed
in the deep ocean.
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In 1943, Maurice Ewing and J. L Worzel
hypothesized that the sound can travel long
distances in the channel to the test.
To test this hypothesis: Both scientists set off an
explosion underwater with 1 pound of TNT in the
Bahamas. To their satisfaction, the sound was
detected 2,000 miles away on the coast of West
Africa.
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SOFAR Channel: Sound Fixing and Ranging Channel
SOFAR channel tends to be located in a layer in the deep
ocean (1km in depth). The sound that is produced in the deep
ocean, travels long distances without any specific amounts of
sound getting to the surface.
The SOFAR Channel tends to be a wave detector, which
measures the sound of the ocean movement due to the
temperature and pressure differences based on the depth of
the ocean.
Sound speed ↑ with increase in pressure. However, the
sound speed ↓ due to decrease in water temperature( 5m/℃).
The origin of the SOFAR channel, is the way that the velocity
of sound differs in water due to the function of ocean.
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Normally, the ocean is divided into horizontal layers and the
temperature in the ocean is measured at the surface layer,
whereas the pressure is measured at the deep layer of the
ocean.
The presence of sound channeling takes place ,due to the
minimum at the vertical sound speed profile in the ocean
which is caused by changes of density in the water. The
density becomes affected by temperature, pressure, and
salinity. These effects cause a change in the speed of sound
in the water, due to the change in density.
In the ocean : as temperature⇩, the speed of sound ⇩, where
the pressure (depth) ⇧, the speed of sound ⇧.
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The SOFAR channel detects how the waves
tend to “bend” downward as the speed of
the sound decreases when ⇩ temperature,
but waves rise back upward as the speed of
sound ⇧ and ⇧ pressure increases.
Thermocline: rapid change in temperature ⇨
Scientists have found that sound waves
have been trapped in the narrow SOFAR
channel due to refraction. They are
continually refracted in the area from
where the bottom of the thermocline
meets the top of the deep isothermic
layer.
Waves may bend downward again as warming
temperatures cause sound velocity to increase.
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Hydrophones are basically underwater
microphones
Hydrophones are devices used to listen to
sound underwater. They convert sound in
water into electrical signals which are then
amplified, recorded, and played on
loudspeakers to measure the property of
sound
Hydrophones listen and record sound, but
they do not make any sound
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Every time travelling sound hits the sea floor, energy is lost
and scattered and is very hard to detect.
Yet even if sound does not hit the sea floor, a very small
amount of energy will still be lost to absorption.
Low frequency sounds that have not hit the ocean surface or
sea floor can then travel through the channel and still be
detected.
The sound travels with minimal velocity and can travel
distances up to 15,500 miles.
 In the ocean, sea animals such as whales use the SOFAR
channel to send sounds across the ocean basins. They can
collaborate even though they are far from one another
like from Asia to America.
 www.youtube.com/watch?v=Dp7BjE9ReKw This video depicts the
types of sounds that are collaborated within the presence of sea
animals and humans( arriving in boats and submersibles)
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Prior to the widespread use of GPS(global positioning
system) equipment, the SOFAR channel also was used for
navigation and the location of marine craft. Some scientists
hypothesize that certain species of whales use the SOFAR
channel to communicate mating calls through long
distances.
 ATOC(Acoustic
Thermometry of Ocean Climate)
 A project that provides data to
measure changes in global
temperature.
 What to expect? It will provide
evidence related to questions as
regards to global warming.
 The SOFAR Channel is a beneficial
tool to measure the oceanic
climate during the ATOC project.
 ATOC(Acoustic
Thermometry of Ocean Climate)
Q: How does the SOFAR channel help in the ATOC project?
A: The SOFAR Channel is beneficial by measuring
differences in the speed of sound that is passed on over
long distances , especially across basins, the data collected
over time averages the variations in temperature and
salinity, and helps ATOC scientists to calculate changes of
the ocean temperature .
The End !!!!!!!