Underwater Sonar
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 Advertising Vexilar FISHERMAN Seeing Underwater World GRAPH CRT Recorder SONAR  US $4.31
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Interesting Video About underwater sonar
Sonar & underwater sounds of Whales, Submarines, Torpedo launch - Moffett Field Museum -1
Seeing Underwater - Sonar Explained
If you've ever watched a movie with a submarine, the chances are you'll be familiar with the word synonymous with navigation underwater sonar. On the other hand though you're less likely to be familiar with how the technology actually works.
Originally developed by the British anti-submarine division in World War One, sonar technology has become widely used in a wide range of fields outside of the original military application. Amazingly, it's actually an example of 'bio-mimetic' technology - basically, nature got their first. Millions of years ahead of humans in fact - sonar is how bats navigate in the dark despite having terrible vision, as well as being used by dolphins for communicating and hunting.
Basically, sonar is a means of acoustic location - locating things via sound. Sonar systems effectively use very low (infrasonic) or very high (ultrasonic) waves to locate objects underwater. Broadly speaking, there are two types of sonar technology: passive and active.
Passive sonar systems simply listen for the sounds and echoes made by other vessels or forms of undersea life. These systems can rarely of use in finding inanimate objects, though the echo from another source of sound can sometimes be used to give some indication of their shape and location. More commonly these systems are used by ships - particularly in warfare; if you don't make sound, you're much harder to see by sonar.
Active sonar systems emit pulses of sounds on the ultrasonic or infrasonic frequencies and can be used to provide a near-real time image of where objects are underwater and their physical characteristics. The pulse is often called a 'ping' (you may remember this noise from the movies) and aside from providing an idea of the position of other vessels and large shoals of fish, it also provides a clear idea of the position of the ocean floor.
The technology may have been developed for military purposes - and indeed still plays a huge part in naval warfare - but it has also proven extremely useful for many civilian maritime applications. Fisheries use sonar to locate their catch, or to locate the position of their nets in the water; sonar devices are used to locate aircraft in case they crash at sea; ships use the technology to navigate shallow waters; and in a field fairly related to its original purpose, its also used as a security measure to counter the threat of sabotage and terrorism at naval bases, commercial ports and oil platforms.
About the Author
Joel Boness is freelance consultant of Security Systems Integrator. While working on this he has gathered knowledge on underwater sonar,maritime security and security system.Visit: http://www.wi-ltd.com/ for more information and services.
How far away is the object?
An engineer at an underwater military station listens for submarines by sending an ultrasound sonar ping that has a frequency of 3.75 MHz. A stationary object is detected when the ping returns 3.00s later. How far away is this object? The speed of sound in seawater is 1533 m/s.
2nd question: A second ping returns with a frequency of 3.80 MHz, indicating that the object is now moving. What is the object's velocity? In which direction is it moving relative to the listening station? (Hint: the direction of sound reverses after the sound reflects off the moving object.)
1. 1533 x 3 = 4599m. Halve it, as the sound must return, so distance is 2,299.5m.
2. 3.8/3.75 = 1.01334:1 ratio.
1.01334 x 1533 = 1,553.44m/sec. apparent velocity of return sound.
1,553.44 - 1,533 = 20.44m/sec. target velocity. As frequency return is higher, the target is moving towards the station.
Find your underwater sonar on Amazon Stores
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Principles of Underwater Sound 3rd Edition $67.50 ... |
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Underwater Acoustics: Analysis, Design and Performance of Sonar $123.81 Offering complete and comprehensive coverage of modern sonar spectrum system analysis, Underwater Acoustics: Analysis, Design and Performance of Sonar provides a state-of-the-art introduction to the subject and has been carefully structured to offer a much-needed update to the classic text by Urick. Expanded to included computational approaches to the topic, this book treads the line between the h... |
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Sonar Signal Processing (Artech House Acoustics Library) $108.00 This discussion of sonar signal processing bridges a number of related fields, including acoustic propagation in the medium, detection and estimation theory, filter theory, digital filtering, sensor array processing, spectral analysis, fast transforms and digital signal processing. The book begins with a discussion of the topics of analogue signalling conditioning, digital filtering, and the calcu... |
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Search for the Titanic Join the quest of the century in an authentic simulation that reflects Man's greatest achievement since the moon landing. The search for the Titanic, the greatest ship to ever fall to the grip of the elements.... |
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Silent Hunter 2 $6.22 Silent Hunter II brings the World War II epic underwater struggle to the PC. Players command a German U-boat with orders to stalk and destroy American and British naval convoys throughout the Atlantic theater. Use sonar and tactical skill to evade antisubmarine patrols, convoy escorts, and enemy aircraft. The adjustable difficulty and realism levels challenge even the most experienced gamers. A mu... |
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Bass Tournament Tycoon $5.16 It's more than a fishing game. Create a world of your own design! It's your bass fishing universe! Create your dream bass lake. Manage your own bass tournament. Compete and win the championship. Play as 3 unique identities. Master of Fish and Water Tournament Tycoon Pro Angler Compete and win tournaments where you create the lake and you set the rules. 18 challenge lev... |
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