What’s a SOFAR?

SOFAR, or Sound Fixing and Ranging Channel, is a naturally-occurring ocean 'channel' that allows sound to carry great distances.

The ocean consists of many zones. Sound can journey via a zone for lots of, typically hundreds of miles. Obtain Infographic | Infographic Textual content

On the peak of World Struggle II, scientists examined a idea that
low-frequency sound may journey lengthy distances within the deep ocean. They
deployed a hydrophone from their analysis vessel, which was anchored off of Woods Gap, Massachusetts. Some 900 miles away, one other ship lowered a four-pound
explosive to a particular depth under the ocean floor. As soon as detonated, the
explosion propelled pulses of sound that traveled the 900 hundred miles
from one ship to the opposite. That’s almost the gap from Washington, DC,
to Des Moines, Iowa!

For the primary time, researchers heard what they termed SOFAR, or a SOund Fixing And Ranging
transmission. Because the scientists famous, “The top of the sound channel transmission was so sharp that it was unattainable for probably the most unskilled observer to overlook it.”

How does SOFAR work? Consider the ocean as consisting of varied zones, or layers — kind of like oil and vinegar salad dressing earlier than it’s shaken up — besides
that ocean layers happen as a result of variations in salinity (salt content material) and
temperature variations. Saltier and colder water lie beneath much less salty, hotter water.

Due to SOFAR, sound emitted at a sure depth bounces between these
numerous layers and might journey for lots of of miles. This up-and-down
bending of low-frequency soundwaves permits soundwaves to journey nice
distances with out the sign dropping important power. By putting
hydrophones on the axis of the sound channel, researchers can document sounds
similar to whale calls, earthquakes, and artifical noise occurring huge
distances from the hydrophones. In some cases, low-frequency sounds can
be heard throughout whole ocean basins.

Infographic Textual content

What’s SOFAR?

This infographic illustrates how SOFAR works. It reveals a ship with a deployed underwater hydrophone receiving the sounds of distant whales, due to the results of the SOFAR channel.

SOFAR, or Sound Fixing and Ranging Channel, is a naturally-occurring ocean “channel” that enables sound to hold nice distances.

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Whales tuned into the SOFAR channel lengthy earlier than scientists. As whales
migrate, they depend on SOFAR to talk over distances of lots of and even hundreds of miles. Ship site visitors and
different human actions lead to a noisier ocean, although—and research present
that louder noise ranges intervene with whale communication. This “cocktail occasion impact” impedes many marine animals that depend upon sound for his or her most elementary
wants, together with meals, communication, safety, copy, and

Final up to date: 02/26/21
Writer: NOAA
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