/soh"nahr/, n.
1. a method for detecting and locating objects submerged in water by echolocation.
2. the apparatus used in sonar. Also called, Brit., asdic.
[1940-45; so(und) na(vigation) r(anging)]

* * *

Technique for detecting and determining the distance and direction of underwater objects by tracking acoustic echoes.

The name derives from sound navigation ranging. Sound waves emitted by or reflected from an object are detected by sonar apparatus and analyzed for information. In active sonar a sound wave is generated that spreads outward and is reflected back by a target object. Passive systems consist simply of receiving sensors that pick up the noise produced by the target (such as a submarine or torpedo). A third kind of sonar, used in communication systems, requires a projector and receiver at both ends. Sonar was first used to detect submarines in 1916. Modern nonmilitary uses include fish finding, depth sounding, mapping of the ocean floor, Doppler navigation (see Doppler effect), and searching for wrecks or other objects in the oceans.

* * *

 (from “sound navigation ranging”), technique for detecting and determining the distance and direction of underwater objects by acoustic means. Sound waves emitted by or reflected from the object are detected by sonar apparatus and analyzed for the information they contain.

      Sonar systems may be divided into three categories. In active sonar systems an acoustic projector generates a sound wave that spreads outward and is reflected back by a target object. A receiver picks up and analyzes the reflected signal and may determine the range, bearing, and relative motion of the target. Passive systems consist simply of receiving sensors that pick up the noise produced by the target (such as a ship, submarine, or torpedo). Waveforms thus detected may be analyzed for identifying characteristics as well as direction and distance. The third category of sonar devices is acoustic communication systems, which require a projector and receiver at both ends of the acoustic path.

      Sonar was first proposed as a means of detecting icebergs. Interest in sonar was heightened by the threat posed by submarine warfare in World War I. An early passive system, consisting of towed lines of microphones, was used to detect submarines by 1916, and by 1918 an operational active system had been built by British and U.S. scientists. Subsequent developments included the echo sounder, or depth detector, rapid-scanning sonar, side-scan sonar, and WPESS (within-pulse electronic-sector-scanning) sonar.

      The uses of sonar are now many. In the military field are a large number of systems that detect, identify, and locate submarines. Sonar is also used in acoustic homing torpedoes, in acoustic mines, and in mine detection. Nonmilitary uses of sonar include fish finding, depth sounding, mapping of the sea bottom, Doppler navigation, and acoustic locating for divers.

      A major step in the development of sonar systems was the invention of the acoustic transducer and the design of efficient acoustic projectors. These utilize piezoelectric crystals (e.g., quartz or tourmaline), magnetostrictive materials (e.g., iron or nickel), or electrostrictive crystals (e.g., barium titanate). These materials change shape when subjected to electric or magnetic fields, thus converting electrical energy to acoustic energy. Suitably mounted in an oil-filled housing, they produce beams of acoustic energy over a wide range of frequencies.

      In active systems the projector may be deployed from an air-launched sonobuoy, hull-mounted on a vessel, or suspended in the sea from a helicopter. Usually the receiving and transmitting transducers are the same. Passive systems are usually hull-mounted, deployed from sonobuoys, or towed behind a ship. Some passive systems are placed on the seabed, often in large arrays, to provide continuous surveillance.

* * *

Universalium. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • sonar — sonar …   Dictionnaire des rimes

  • Sonar — Monitore im US amerikanischen Atom U Boot USS Toledo (SSN 769) Sonar ist ein „Verfahren zur Ortung von Gegenständen im Raum und unter Wasser mithilfe ausgesandter Schallimpulse“.[1] Das Wort ist ein englisches Akronym von sound navigation and… …   Deutsch Wikipedia

  • SONAR — On désigne sous le nom de sonar l’ensemble des techniques qui permettent de transmettre et de recevoir de l’information à travers le milieu marin en utilisant les ondes de vibrations élastiques. L’eau propage ces vibrations à de grandes distances …   Encyclopédie Universelle

  • Sónar — is a annual three day music festival held in Barcelona, Spain. It is described officially as a festival of Advanced Music and Multimedia Art. Music is by far the main aspect of the festival.The festival runs for three days and nights, usually… …   Wikipedia

  • Sonar FM — Localización Santiago Área de radiodifusión Santiago Frecuencia 105.7 FM (Santiago) Primera emisión 29 de julio de 2009 …   Wikipedia Español

  • sonar — verbo intransitivo 1. Producir (una cosa) sonido o ruido: Una explosión estridente sonó fuera del parque. 2. Tener (una letra) un determinado valor fónico: La letra hache no suena. La d entre vocales suena fricativa …   Diccionario Salamanca de la Lengua Española

  • sonar — SONÁR, sonare, s.n. 1. Principiu natural şi tehnic de detectare a unui obiect în spaţiu, bazat pe emisia şi reflectarea undelor. 2. Detector sonic pentru telecomunicaţii subacvatice, folosit pentru reperarea unor obiecte submarine. – Din fr.… …   Dicționar Român

  • sonar — ‘Sistema de localización submarina mediante sonidos o ultrasonidos’. Procede del acrónimo inglés so[und] na[vigation and] r[anging], creado por analogía con radar (→ radar); por ello, resulta preferible su pronunciación como voz aguda en español …   Diccionario panhispánico de dudas

  • sonar — (Del lat. sonāre). 1. intr. Dicho de una cosa: Hacer o causar ruido. 2. Dicho de una letra: Tener valor fónico. 3. Mencionarse, citarse. Su nombre no suena en aquella escritura. 4. Dicho de una cosa: Tener visos o apariencias de algo. La… …   Diccionario de la lengua española

  • soñar — (Del lat. somniāre). 1. tr. Representarse en la fantasía imágenes o sucesos mientras se duerme. U. t. c. intr.) 2. Discurrir fantásticamente y dar por cierto y seguro lo que no lo es. U. t. c. intr.) 3. Temblar a alguien, acordarse de su venganza …   Diccionario de la lengua española

  • Sonar — Sonar: Cakewalk Sonar  звуковой редактор Sonar (группа) Список значений слова или словосочетания со ссылками на соответствующие статьи. Если вы попа …   Википедия

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”