Sonar principle and application

First, what is sonar Sonar is an electronic device that uses underwater sound waves to detect, locate and communicate underwater targets. It is the most widely used and important device in underwater acoustics. Sonar technology has a history of 100 years, it was invented in 1906 by Lewis Nixon of the British Navy. The first sonar he invented was a passive listening device, mainly used to detect icebergs. This technology, which was applied to the battlefield during the First World War, was used to detect submarines lurking in the water. At present, sonar is the main technology used by navies for underwater surveillance, which is used to detect, classify, locate and track underwater targets; conduct underwater communication and navigation, and ensure the tactical maneuvering and tactical maneuvering of ships, anti-submarine aircraft and anti-submarine helicopters. Use of underwater weapons. In addition, sonar technology is also widely used in torpedo guidance, mine fuzes, as well as fish detection, offshore oil exploration, ship navigation, underwater operations, hydrographic surveys, and survey of seabed geology and landforms. Second, the working principle of sonar Sound waves are an important means of observation and measurement. For observation and measurement in water, only sound waves are uniquely endowed. This is due to the fact that other detection methods have very short working distances, and the penetrating ability of light in water is very limited. Even in the clearest seawater, people can only see objects within a dozen to tens of meters; electromagnetic waves are also in the water. The attenuation is too fast, and the shorter the wavelength, the greater the loss. Even if high-power low-frequency electromagnetic waves are used, they can only travel tens of meters. However, the attenuation of sound waves propagating in water is much smaller. If a bomb of several kilograms is exploded in the deep-sea channel, the signal can still be received at a distance of 20,000 kilometers. The low-frequency sound waves can also penetrate several kilometers of the seabed. And get the information in the stratum. Measurements and observations in water have not yet been found to be more effective than sound waves. 3. Sonar structure and classification Sonar device generally consists of three parts: array, electronic cabinet and auxiliary equipment. The array is composed of underwater acoustic transducers arranged and combined in a certain geometric figure, and its shape is usually spherical, cylindrical, flat or linear, and can be divided into receiving arrays, transmitter arrays or integrated transceiver arrays. Electronic cabinets generally have sub-systems such as transmission, reception, display and control. Auxiliary equipment includes power supply equipment, connecting cables, underwater junction boxes and repeaters, lifting, slewing, pitching, retracting, towing, hoisting, throwing and other devices matched with the transmission control of the sonar array, as well as sonar shroud, etc. Transducer is an important device in sonar, it is a device for mutual conversion between acoustic energy and other forms of energy such as mechanical energy, electrical energy, and magnetic energy. It has two purposes: one is to transmit sound waves underwater, called 'transmitting transducer', which is equivalent to a speaker in the air; the other is to receive sound waves underwater, called 'receiving transducer', which is equivalent to air microphone in . In actual use, transducers are often used to transmit and receive sound waves at the same time, and transducers specially used for receiving are also called 'hydrophones'. The working principle of the transducer is to use the piezoelectric effect or the magnetostrictive effect of certain materials to stretch under the action of an electric or magnetic field. The classification of sonar can be divided into various sonars according to their working methods, equipment objects, tactical uses, array carrying methods and technical characteristics. For example, it can be divided into active sonar and passive sonar according to the working mode; according to the equipment object, it can be divided into surface ship sonar, submarine sonar, aviation sonar, portable sonar and coastal sonar. Active sonar: Active sonar technology means that the sonar actively emits sound waves to 'illuminate' the target, and then receives the echoes reflected by the target in the water to determine the parameters of the target. Most use the pulse system, and some use the continuous wave system. It is evolved from a simple echo detection instrument. It actively transmits ultrasonic waves, and then receives and measures the echoes for calculation. It is suitable for detecting icebergs, reefs, shipwrecks, sea depths, fish schools, mines, and concealed submarines with closed engines; Passive sonar: Passive sonar technology means that sonar passively receives radiated noise generated by underwater targets such as ships and signals emitted by underwater acoustic equipment to determine the orientation of the target. It evolved from a simple hydrophone. It listens to the noise emitted by the target and determines the position and certain characteristics of the target. It is especially suitable for submarines that cannot make sounds to expose themselves but want to detect the activities of enemy ships. Four sonar installation and application Traditionally, the main location for sonar installation in submarines is at the forefront. Since modern submarines rely heavily on the detection effect of passive sonar, the huge radio device not only increases the diameter of the submarine, it was originally in this position. The torpedo tubes on top also had to yield their positions obediently and retreat to the sides.