Nuclear submarineA nuclear submarine is a submarine powered by a nuclear reactor, but not necessarily nuclear-armed. Nuclear submarines have considerable performance advantages over "conventional" (typically diesel-electric) submarines. Nuclear propulsion, being completely independent of air, frees the submarine from the need to surface frequently, as is necessary for conventional submarines.
Multibeam echosounderA multibeam echosounder (MBES) is a type of sonar that is used to map the seabed. It emits acoustic waves in a fan shape beneath its transceiver. The time it takes for the sound waves to reflect off the seabed and return to the receiver is used to calculate the water depth. Unlike other sonars and echo sounders, MBES uses beamforming to extract directional information from the returning soundwaves, producing a swathe of depth soundings from a single ping.
Hull (watercraft)A hull is the watertight body of a ship, boat, or flying boat. The hull may open at the top (such as a dinghy), or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, derrick, or mast. The line where the hull meets the water surface is called the waterline. There is a wide variety of hull types that are chosen for suitability for different usages, the hull shape being dependent upon the needs of the design.
SOFAR channelThe SOFAR channel (short for sound fixing and ranging channel), or deep sound channel (DSC), is a horizontal layer of water in the ocean at which depth the speed of sound is at its minimum. The SOFAR channel acts as a waveguide for sound, and low frequency sound waves within the channel may travel thousands of miles before dissipating. An example was reception of coded signals generated by the Navy chartered ocean surveillance vessel Cory Chouest off Heard Island, located in the southern Indian Ocean (between Africa, Australia and Antarctica), by hydrophones in portions of all five major ocean basins and as distant as the North Atlantic and North Pacific.
BuoyA buoy (ˈbuː.i,_bɔɪ) is a floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. Race course marker buoys are used for buoy racing, the most prevalent form of yacht racing and power boat racing. They delimit the course and must be passed to a specified side. They are also used in underwater orienteering competitions. Emergency wreck buoys provide a clear and unambiguous means of temporarily marking new wrecks, typically for the first 24–72 hours.
Autonomous underwater vehicleAn autonomous underwater vehicle (AUV) is a robot that travels underwater without requiring continuous input from an operator. AUVs constitute part of a larger group of undersea systems known as unmanned underwater vehicles, a classification that includes non-autonomous remotely operated underwater vehicles (ROVs) – controlled and powered from the surface by an operator/pilot via an umbilical or using remote control. In military applications an AUV is more often referred to as an unmanned undersea vehicle (UUV).
ReverberationReverberation (also known as reverb), in acoustics, is a persistence of sound after it is produced. Reverberation is created when a sound or signal is reflected. This causes numerous reflections to build up and then decay as the sound is absorbed by the surfaces of objects in the space – which could include furniture, people, and air. This is most noticeable when the sound source stops but the reflections continue, their amplitude decreasing, until zero is reached.
SpectrogramA spectrogram is a visual representation of the spectrum of frequencies of a signal as it varies with time. When applied to an audio signal, spectrograms are sometimes called sonographs, voiceprints, or voicegrams. When the data are represented in a 3D plot they may be called waterfall displays. Spectrograms are used extensively in the fields of music, linguistics, sonar, radar, speech processing, seismology, and others. Spectrograms of audio can be used to identify spoken words phonetically, and to analyse the various calls of animals.
Acoustic torpedoAn acoustic torpedo is a torpedo that aims itself by listening for characteristic sounds of its target or by searching for it using sonar (acoustic homing). Acoustic torpedoes are usually designed for medium-range use, and often fired from a submarine. The first passive acoustic torpedoes were developed nearly simultaneously by the United States Navy and the Germans during World War II. The Germans developed the G7e/T4 Falke, which was first deployed by the submarines , and in March 1943.
Length measurementLength measurement, distance measurement, or range measurement (ranging) refers to the many ways in which length, distance, or range can be measured. The most commonly used approaches are the rulers, followed by transit-time methods and the interferometer methods based upon the speed of light. For objects such as crystals and diffraction gratings, diffraction is used with X-rays and electron beams. Measurement techniques for three-dimensional structures very small in every dimension use specialized instruments such as ion microscopy coupled with intensive computer modeling.
