Facts about Sonar
Sonars have been developed for measuring a ship's velocity either relative to the water or to the bottom.
SODAR—which is an upward-looking, in-air sonar—is used for atmospheric investigations.
Sonars have continued to be developed by many countries, including Russia, for both military and civil uses.
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An imitation of the humpback whale's sonar was conducted in the redirection of Humphrey the whale, who deviated from his normal migration path to enter San Francisco Bay.
Relatively simple sonars such as echo sounders can be promoted to seafloor classification systems via add-on modules, converting echo parameters into sediment type.
Processing from the sonobuoys or dipping sonar can be on the aircraft or on ship.
The signal is naturally attenuated by distance, but modern sonar systems are very sensitive, i.e.
Sonars which act as beacons are fitted to aircraft to allow their location in the event of a crash in the sea.
Military sonars often have multiple beams to provide all-round cover while simple ones only cover a narrow arc.
Mine Countermeasure (MCM) Sonar is a specialized type of sonar used for detecting small objects.
Sonars have been developed that can be used to characterize the sea bottom into, for example, mud, sand, and gravel.
In World War II, the Americans used the term SONAR for their systems, coined as the equivalent of RADAR.
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Special short range sonars have been developed to allow measurements of water velocity.
In 1916, under the British Board of Invention and Research, Canadian physicist Robert Boyle took on the active sonar project with A B Wood, producing a prototype for testing in mid-1917.
An example of a hull mounted MCM sonar is the Type 2093 while the SSQ-32 mine hunting sonar is a VDS design.
Low frequency sonars such as GLORIA have been used for continental shelf wide surveys while high frequency sonars are used for more detailed surveys of smaller areas.
Some marine animals, such as whales and dolphins, use echolocation systems similar to active sonar to locate predators and prey.
Side scan sonars can be used to derive maps of the topography of an area by moving the sonar across it just above the bottom.
The display of most passive sonars used to be a two-dimensional waterfall display.
An explanation of their operation is given in synthetic aperture sonar.
Intermittent sound sources (such as a wrench being dropped) may also be detectable to passive sonar.
Helicopters can be used for antisubmarine warfare by deploying fields of active/passive sonobuoys or can operate dipping sonar, such as the AQS-13.
Having heard the signal, it is easy to identify the type of sonar (usually with its frequency) and its position (with the sound wave's energy).
Various synthetic aperture sonars have been built in the laboratory and some have entered use in mine-hunting and search systems.
Active sonar is also used to measure distance through water between two sonar transducers or a combination of a hydrophone (underwater acoustic microphone) and projector (underwater acoustic speaker).
Mines (acoustic mines) may be fitted with a sonar to detect, localize, and recognize the required target.
Today, commercial fishing vessels rely almost completely on acoustic sonar and sounders to detect fish.
Research on sonar and underwater sound was expanded greatly, particularly in the US.
Limpet Mine Imaging Sonar (LIMIS) is a hand-held or ROV-mounted imaging sonar designed for patrol divers (combat frogmen or clearance divers) to look for limpet mines in low visibility water.
SONAR (SOund Navigation And Ranging) — or sonar — is a technique that uses sound propagation under water (primarily) to navigate, communicate, or detect other vessels.
Simple sonars generally use the former with a filter wide enough to cover possible Doppler changes due to target movement, while more complex ones generally include the latter technique.
The frequencies used in sonar systems vary from infrasonic to ultrasonic.
Dedicated sonars can be fitted to ships and submarines for underwater communication.
Companies such as Marport Canada, Wesmar, Furuno, Krupp, and Simrad make a variety of sonar and acoustic instruments for the deep sea commercial fishing industry.
Integrated Navigation Sonar System (INSS) is a small flashlight-shaped handheld sonar for divers that displays range.
The sonar hydrophones may be towed behind the ship or submarine in order to reduce the effect of noise generated by the watercraft itself.
When active sonar is used, scattering occurs from small objects in the sea as well as from the bottom and surface.
Using active sonar is somewhat hazardous however, since it does not allow the sonar to identify the target, and any vessel around the emitting sonar will detect the emission.
The sonar is an echo-sounder with a directional capability that can show fish or other objects around the vessel.
High-powered sonar transmitters may harm marine animals, although the precise mechanisms for this are not well understood.
Some civilian sonars approach active military sonars in capability, with quite exotic three-dimensional displays of the area near the boat.
Until recently, ship sonars were usually with hull mounted arrays, either amidships or at the bow.
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Passive sonar has a wide variety of techniques for identifying the source of a detected sound.
Similarly, to overcome reverberation, an active sonar needs to transmit in a narrow beam.
Small sonars have been fitted to Remotely Operated Vehicles (ROV) and Unmanned Underwater Vehicles (UUV) to allow their operation in murky conditions.
Submarines rely on sonar to a greater extent than surface ships as they cannot use radar at depth.
Passive sonar systems may have large sonic databases, however final classification is generally performed manually by the sonar operator.
Passive sonar on vehicles is usually severely limited because of noise generated by the vehicle.
Sonar operation is affected by variations in sound speed, particularly in the vertical plane.
Environmental impacts of the operation of active sonar are required to be carried out by U.S. law.
A kind of sonar called mid-frequency sonar has been correlated with mass cetacean strandings throughout the world's oceans, and has therefore been singled out by environmentalists as causing the death of marine mammals.
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Procedures for minimizing the impact of sonar are developed in each case where there is significant impact.
The target signal (if present) together with noise is then passed through various forms of signal processing, which for simple sonars may be just energy measurement.
In 1948, with the formation of NATO, standardization of signals led to the dropping of ASDIC in favor of sonar.
Work on sonar had also been carried out in many other counties, notably in Germany.
Active sonar creates a pulse of sound, often called a "ping," and then listens for reflections (echo) of the pulse.