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Sonar

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Sonar is a technique used to navigate, communicate, and detect objects in water. The name is an acronym for sound navigation and ranging, or sonic navigation and ranging. It relies on the science of underwater acoustics, which is the study of how sound moves through water.

Sonar Principle EN
Sonar Principle EN

Humans use this technology to find vessels, map the sea floor, or guide robots. It is a vital tool for understanding the physical world beneath the ocean surface.

There are two primary ways that sonar technology operates: passive and active. Passive sonar involves listening for the sounds already being made by other vessels. In contrast, active sonar works by emitting pulses of sound and listening for the resulting echoes.

Sonar Principle EN
Sonar Principle EN

In an active system, an acoustic transducer generates a sound wave. This wave travels through the water until it hits a target object. The sound then reflects off that object and travels back to the receiver. By measuring these echoes, operators can determine the location and characteristics of the target.

Different types of hardware are used to manage these sound waves. For example, some ships use variable depth sonar (VDS), which can be towed at different levels.

Variabel dybde sonar (VDS) på et af søværnets skibe af Thetis-klassen
Variabel dybde sonar (VDS) på et af søværnets skibe af Thetis-klassen

Other systems use hydrophones, which are devices designed to listen to underwater sounds. Early hydrophones used carbon button microphones, but modern versions use advanced materials. Engineers have developed projectors using materials like Terfenol-D or lead magnesium niobate (PMN) to create sound.

Watch floor
Watch floor

Humans have experimented with sound detection for centuries. In 1490, Leonardo da Vinci used a tube inserted into the water to detect vessels by ear. The modern era of sonar was shaped by the disaster of 1912. Following the sinking of the Titanic, Lewis Fry Richardson filed a patent for an underwater echo-ranging device. In 1914, Canadian engineer Reginald Fessenden tested a system in the Grand Banks off Newfoundland. His "Fessenden oscillator" operated at 500 Hz and successfully detected an iceberg using echo ranging.

Miinitraaleri "Virsaitis" vrakk
Miinitraaleri "Virsaitis" vrakk

World War I and World War II drove rapid technological growth. The British developed a secret system known as ASDIC. This acronym originally stood for "Anti-Submarine Division," though a later story claimed it meant "Allied Submarine Detection Investigation Committee."

ASDIC
ASDIC

By 1923, the British 6th Destroyer Flotilla had vessels equipped with ASDIC. During the war, tactical improvements like the "creeping attack" were developed. This involved two ships: one "directing ship" to track the target and one attacking ship. New weapons like Hedgehogs and Squids were also created to solve the "blind spot" problem during attacks.

In the United States, significant research occurred during the 1930s and 1940s. American engineers discovered thermoclines, which are layers in the water that affect how sound waves travel. The term "SONAR" was coined by Frederick Hunt to match the term "RADAR."

Researchers like J. Warren Horton applied vacuum tubes to improve signal detection. They also replaced unreliable Rochelle salt crystals with a superior material called ammonium dihydrogen phosphate (ADP). ADP crystals were highly reliable because they had zero aging characteristics.

Today, sonar technology is incredibly diverse and specialized. It is used in fish finders to locate marine life.

Fishfinder
Fishfinder

It is also used for hydrographic surveys to map the ocean floor.

Sonar operations by survey ship
Sonar operations by survey ship

Even in atmospheric studies, a version called sodar is used to investigate the air. Much like dolphins and bats use sound to navigate their environments, humans use sonar to bridge the gap between the surface and the deep ocean.

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🖼️ Images & Media (14)
File:Motte-Picquet-tugged-sonar.jpg
Motte-Picquet-tugged-sonar.jpg
File:Miinitraaleri "Virsaitis" vrakk.jpg
Miinitraaleri "Virsaitis" vrakk.jpg
File:ASDIC.png
ASDIC.png
File:Sonar Principle EN.svg
Sonar Principle EN.svg
File:Undersea bubble clouds.jpg
Undersea bubble clouds.jpg
File:TWIPS picture 2.png
TWIPS picture 2.png
File:Variabel dybde sonar (VDS) på et af søværnets skibe af Thetis-klassen.jpg
Variabel dybde sonar (VDS) på et af...
File:SH-3H HS-15 lowers AQS-13 sonar 1979.JPEG
SH-3H HS-15 lowers AQS-13 sonar 1979.JPEG
File:Watch floor.gif
Watch floor.gif
File:US Navy 030223-N-7479T-011 An AN-PQS-2A, a handheld sonar device used to aid in the search of the Toledo Bend Reservoir for debris from the Space Shuttle Columbia.jpg
US Navy 030223-N-7479T-011 An AN-PQS-2A,...
File:Fishfinder.jpg
Fishfinder.jpg
File:Sonar operations by survey ship.jpg
Sonar operations by survey ship.jpg

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