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25-458: Sofar may refer to: Sofar bomb (SOund Fixing And Ranging bomb), a long-range position-fixing system that uses explosive sounds in the deep sound channel of the ocean SOFAR channel (SOund Fixing And Ranging channel), a horizontal layer of water in the ocean centered on the depth at which the speed of sound is minimum Sofar Sounds , music events company See also [ edit ] Shofar ,

50-531: A 30 m (98 ft) in depth surface duct and a shallow sound channel at 200 m (656 ft). As the path turns northward, a station at 43º south, 16º east showed the profile reverting to the SOFAR type at 800 m (2,625 ft). The first practical application began development during World War II when the United States Navy began experimenting and implementing the capability to locate

75-552: A method for ships to accurately report their position without use of radio, or to find crashed planes and ships. During the war, the primary model of sofar bomb used by the United States was the Mk-22. It worked exceptionally well , and had an adjustable fuse for different depth detonations. The bomb was used with a chart that detailed the depth of the deep sound channel, so that the 4 pounds (1.8 kg) of TNT would explode at

100-549: A musical instrument Sawfar , a village in Lebanon Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Sofar . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Sofar&oldid=934332132 " Category : Disambiguation pages Hidden categories: Short description

125-418: A path that oscillates across the SOFAR channel axis so that a single signal will have multiple arrival times with a signature of multiple pulses climaxing in a sharply defined end. That sharply defined end representing a near axial arrival path is sometimes termed the SOFAR finale and the earlier ones the SOFAR symphony. Those effects are due to the larger sound channel in which ray paths are contained between

150-425: A pioneer of oceanography and geophysics , first suggested putting small hollow metal spheres in pilots' emergency kits during World War II . The spheres would implode when they sank to the sofar channel , acting as a secret homing beacon to be received by microphones on coastlines that could pinpoint downed pilots' positions. This technology proved to be useful for the naval conflicts during World War II by providing

175-479: A surface duct. A 1980 report by Naval Ocean Systems Center gives examples in a study of a great circle acoustic path between Perth, Australia and Bermuda with data at eight locations along the path. At both Perth and Bermuda the sound channel axis occurs at a depth of around 1,200 m (3,937 ft). Where the path meets the Antarctic Convergence at 52º south there is no deep sound channel but

200-445: Is different from Wikidata All article disambiguation pages All disambiguation pages Sofar bomb In oceanography , a sofar bomb (Sound Fixing And Ranging bomb), occasionally referred to as a sofar disc, is a long-range position-fixing system that uses impulsive sounds in the deep sound channel ( SOFAR channel ) of the ocean to enable pinpointing of the location of ships or crashed planes. The deep sound channel

225-404: Is ideal for the device, as the minimum speed of sound at that depth improves the signal's traveling ability. A position is determined from the differences in arrival times at receiving stations of known geographic locations. The useful range from the signal sources to the receiver can exceed 3,000 miles (4,800 km). For this device to work as intended, it must have several qualities. Firstly,

250-506: The Ascension Island Missile Impact Locating System hydrophones at an intermediate range of 9,200 km (5,700 mi; 5,000 nmi) from the source found "surprisingly high" signal-to-noise ratios , ranging from 19 to 30 dB, with unexpected phase stability and amplitude variability after a travel time of about 1 hour, 44 minutes and 17 seconds. Within the duct sound waves trace

275-587: The Juan de Fuca Ridge in time for research vessels to investigate. As a result of that success, PMEL developed its own hydrophones for deployment worldwide to be suspended in the SOFAR channel by a float and anchor system. Mysterious low-frequency sounds , attributed to fin whales ( Balaenoptera physalus ), are a common occurrence in the channel. Scientists believe fin whales may dive down to this channel and sing to communicate with other fin whales many kilometers away. The novel The Hunt for Red October describes

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300-587: The Lebedev Physics Institute in the 1940s. In testing the concept in 1944 Ewing and Worzel hung a hydrophone from Saluda , a sailing vessel assigned to the Underwater Sound Laboratory , with a second ship setting off explosive charges up to 900 nmi (1,000 mi; 1,700 km) away. Temperature is the dominant factor in determining the speed of sound in the ocean. In areas of higher temperatures (e.g. near

325-654: The Atlantic. The first major exploitation of the SOFAR channel was for ocean surveillance in a classified program that led to the Sound Surveillance System (SOSUS). That system remained classified from inception until the fixed systems were augmented by mobile arrays to become the Integrated Undersea Surveillance System with the mission and nature of the system declassified in 1991. Earthquake monitoring through

350-665: The Bermuda station are maintained by the Woods Hole Oceanographic Institute (WHOI). In the recent past SOFAR sources were deployed for special purposes in the RAFOS application. One such system deployed bottom moored sources off Cape Hatteras , off Bermuda and one on a seamount to send three precisely timed signals a day to provide approximately five-kilometre (3.1 mi; 2.7 nmi) accuracy. The first application quickly became of intense interest to

375-480: The Navy for reasons other than locating downed air crews. A Navy decision in 1949 led to studies by 1950 recommending the passive sonar potential of the SOFAR channel be exploited for the Navy's Anti-Submarine Warfare (ASW) effort. The recommendation included that $ 10 million a year be spent on research and development of the system. By 1951 a test array had proven the concept and by 1952 additional stations were ordered for

400-419: The bomb needs to detonate at the correct depth, so that it can take full advantage of the deep sound channel. The sofar bomb has to sink fast enough so that it reaches the required depth within a reasonable amount of time (usually about 5 minutes). To determine the position of a sofar bomb that has been detonated, three or more naval stations combine their reports of when they received the signal. Detonating

425-509: The correct time for its location (as the deep sound channel's actual depth varies with areas of the ocean). Its main safety mechanism was the detonator that could not trigger without a water pressure that corresponded to at least 750 feet (230 m). Sofar channel This phenomenon is an important factor in ocean surveillance. The deep sound channel was discovered and described independently by Maurice Ewing and J. Lamar Worzel at Columbia University and Leonid Brekhovskikh at

450-402: The explosion of a SOFAR bomb used as a distress signal by downed pilots. The difference in arrival times of the source at an unknown location and known locations allowed computation of the source's general location. The arrival times form hyperbolic lines of position similar to LORAN . The reverse, detection of timed signals from known shore positions at an unknown point, allowed calculation of

475-404: The ocean surface), there is higher sound speed. Temperature decreases with depth, with sound speed decreasing accordingly until temperature becomes stable and pressure becomes the dominant factor. The axis of the SOFAR channel lies at the point of minimum sound speed at a depth where pressure begins dominating temperature and sound speed increases. This point is at the bottom of the thermocline and

500-567: The position at that point. That technique was given the name of SOFAR backwards: RAFOS. RAFOS is defined in the 1962 edition of The American Practical Navigator among the hyperbolic navigation systems. The early applications relied on fixed shore stations, often termed SOFAR stations. Several became acoustic research facilities as did the Bermuda SOFAR Station which was involved in the Perth to Bermuda experiment. The records of

525-442: The sofar bomb in the deep sound channel gives it huge benefits. The channel itself helps keep the sound waves contained within the same depth, as the rays of sound that have an upward or downward velocity are pushed back towards the deep sound channel because of refraction . Because the sound waves do not spread out vertically, the horizontal sound rays maintain far more strength than they would otherwise. This makes it far easier for

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550-405: The stations on shore to pick up and analyze the signal. Usually, the blasts use frequencies between 30 and 150 Hz, which also helps stop the signal from weakening too much. A side effect of this is that the slightly higher frequencies of sound waves emitted move a bit faster than the lower frequencies, making the signal that the naval stations hear have a longer duration. Dr. Maurice Ewing ,

575-464: The surface and critical depth. Critical depth is the point below the sound speed minimum axis where sound speed increases to equal the maximum speed above the axis. Where the bottom lies above critical depth the sound is attenuated, as is any ray path intersecting the surface or bottom. The channel axis varies most with its location reaching the surface and disappearing at high latitudes (above about 60°N or below 60°S) but with sound then traveling in

600-435: The top of the deep isothermal layer and thus has some seasonal variance. Other acoustic ducts exist, particularly in the upper mixed layer , but the ray paths lose energy with either surface or bottom reflections. In the SOFAR channel, low frequencies, in particular, are refracted back into the duct so that energy loss is small and the sound travels thousands of miles. Analysis of Heard Island Feasibility Test data received by

625-604: The use of SOSUS after limited civilian access was granted to the Pacific Marine Environmental Laboratory (PMEL) of the National Oceanic and Atmospheric Administration in 1991 revealed ten times the number of offshore earthquakes with better localization than with land-based sensors. The SOSUS detection could sense earthquakes at about magnitude two rather than magnitude four. The system detected seafloor spreading and magma events in

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