The so-called sonar is the abbreviation of sound navigation and ranging. It is a technical equipment for searching, locating, identifying and tracking underwater targets by using the physical characteristics of high speed and small attenuation of sound waves in water. It is known as the "clairvoyance" and "windward ear" of underwater. During World War II, the British destroyer Walker used sonar to locate the German submarine U-99 and sank it to the bottom of the sea.
The first sonar in the world was invented by French physicist Langevin in 197 1 year. The working principle of sonar is echo detection (similar to radar). Sonar is divided into passive sonar (or noise sonar) and active sonar according to its working mode, and now sonar has both. Take passive sonar as an example: when the target moves in water or on the water surface, it will produce mechanical vibration and noise, which will be transmitted to sonar transducer through seawater medium. The transducer converts sound waves into electrical signals, which are then transmitted to the receiver. After amplification, they will be transmitted to the display console for display, audiometry and positioning. Passive sonar has good concealment and strong ability to identify targets, but it cannot detect static targets. Active sonar can solve this problem, but it is easy to expose itself and has a short detection distance.
At first, sonar was mainly used to detect enemy submarines. With the development of technology, sonar has developed to the fifth generation, that is, digital sonar, and its performance has been greatly improved. In addition to military purposes, it is used for submarine search, mine detection, submarine early warning, underwater navigation, underwater (torpedoes, mines, etc. ) guidance and confrontation, but also for marine resources exploration, research and development, such as detecting fish and shrimp, detecting ocean depth, submarine rocks, sunken ships, oil pipes, submarine cables and underwater obstacles, submarine oil and gas, etc.
sonar
Sound wave is an important means of observation and measurement. Interestingly, the word "sound" in English means "sound" as a noun and "detection" as a verb, which shows the close relationship between sound and detection.
When observing and measuring in water, only sound waves are unique. This is because the action distance of other detection means is very short, and the penetration ability of light in water is very limited. Even in the clearest seawater, people can only see objects in the range of ten meters to dozens of meters. Electromagnetic waves decay too fast in water, and the shorter the wavelength, the greater the loss. Even if high-power low-frequency electromagnetic waves are used, they can only propagate for tens of meters. But the attenuation of sound wave propagation in water is much smaller. A few kilograms of bombs exploded in the deep-sea passage, and signals could be received 20 thousand kilometers away. Low-frequency sound waves can also penetrate the strata thousands of meters under the sea and obtain information in the strata. So far, there is no more effective means to measure and observe in water than sound waves.
Sonar is a device that uses sound waves to detect and locate underwater targets, and it is the most widely used and important device in hydroacoustics. It is the translation of the word SONAR, which is the abbreviation of sound navigation and ranging.
Sonar can be divided into active sonar and passive sonar. Active sonar is developed from a simple echo detection instrument. It actively emits ultrasonic waves, and then collects and calculates the echoes. It is suitable for detecting icebergs, reefs, sunken ships, ocean depths, fish schools, mines and hidden submarines with engines turned off. On the other hand, passive sonar is developed from simple hydrophone. It monitors the noise emitted by the target and judges the position and some characteristics of the target. It is especially suitable for submarines that cannot expose themselves but want to detect the activities of enemy ships.
Transducer is an important device in sonar, which converts acoustic energy into mechanical energy, electrical energy, magnetic energy and other forms of energy. It has two purposes: one is to emit sound waves underwater, which is called "transmitting transducer", which is equivalent to a loudspeaker in the air; The second is to receive sound waves underwater, which is called "receiving transducer", which is equivalent to a microphone in the air (commonly known as "microphone" or "microphone"). Transducers are often used to transmit and receive sound waves at the same time in practical use, and the transducers specially used for receiving are also called "hydrophones". The working principle of transducer is that some materials expand and contract under the action of electric field or magnetic field, resulting in piezoelectric effect or magnetostrictive effect.
Like the development of many technologies, the demand of society and the progress of technology promote the development of sonar technology.
The "shipwreck in the ice sea" incident prompted the birth of the echo detector. 191April 14, the British luxury passenger ship Titanic sank after colliding with an iceberg in the North Atlantic on its maiden voyage to the United States. The biggest shipwreck in history caused a great shock, prompting scientists to study the detection and location of icebergs. British scientist L.F. Sun Guohao applied for two patents five days and 1 month after the sinking of the ship, using sound waves to detect obstacles in air and water, and proposed using directional emission transducer, but it did not continue to work hard to realize his patent. 19 13, American scientist R·A· Fessenden applied for a number of patents for underwater detection, and made the first echo detector by using the moving-coil transducer designed by himself. 1965438+In April 2004, he successfully detected an iceberg 2 nautical miles (3.7 kilometers) away with the sound wave of 500- 1000 Hz emitted by this equipment.
Then, World War I broke out in 19 14, which greatly promoted the development of underwater acoustic positioning directional weapons. During the First World War, German submarines launched the "Infinite Submarine War", which was invincible for a while, posing a great threat to the maritime transportation of the allies and other countries, and almost interrupted transatlantic transportation. The allies and other countries were very angry and successively developed underwater acoustic equipment to detect underwater submarines. At that time, many famous scientists took part in this work. C. Chilovsky, a young electrical engineer in Russia, started the development of underwater acoustic detection equipment under the influence of the shipwreck in the ice sea very early. After the start of World War I, he recovered from illness in the Swiss mountains and felt the importance of anti-submarine warfare. After that, he turned his research to using high-frequency sound waves for submarines. The idea of echo detection. His suggestion was adopted by the French government in February 19 15, and put into practice by the famous French physicist Professor Langevin. Langevin and Chilovsky decided to use high-frequency ultrasound. They use mica electrostatic transducer, put mica sheet in two electrodes, apply AC voltage to emit sound waves, and use carbon particle microphone as receiving transducer. With such simple equipment, the intercropping propagation experiments on both sides of the Seine River were successful at the end of 19 15 and the beginning of 19 16, and two kilometers of unidirectional propagation was realized. The news of their success spread to Britain, and Britain also set up a team to develop echo detectors.
In order to increase the detection distance, it is necessary to improve the transmission intensity and reception sensitivity. They use the piezoelectric effect discovered in 1880 ~ 188 1 year to generate and receive ultrasonic waves, but this piezoelectric effect is still very weak. At that time, a high-power electron tube high-frequency amplifier was invented in the field of electronics, which was just used to amplify the piezoelectric effect. The remaining problem is to find a timely single crystal with piezoelectric effect.
1917 10/in June, langevin finally persuaded an optician to give away the timely single crystal exhibit with a diameter of about10 inch that he had treasured for many years, cut off the wafer from it, made it into a timely piezoelectric receiving transducer, and then matched it with a mica electrostatic transmitting transducer to complete the project. Later, it was used to replace mica to complete 8 km one-way signal transmission.
After learning of Langevin's success, the British searched everywhere for large crystals. After all the crystal exhibits in geological museum, England, they went to the French crystal optician. They found a large number of crystals from the warehouse and made echo detectors. After listening to the introduction of Langevin's success by the British and French delegations, American scientists also strengthened their research work in this field.
During this period, people also developed passive sonar, which can determine their position by listening to the noise of enemy ships. The earliest passive sonar only had two receivers, which were heard through the stethoscope carried on the human head. In order to determine the distance accurately, a linear array with multiple hydrophones on each side was later developed. By rotating the linear array, the position of enemy ships can be judged by ears.
Regrettably, until the end of World War I, they did not make further achievements. Ultrasonic echo detection succeeded too late to show its great power in the First World War. However, the outstanding achievements of Langevin and his colleagues pioneered the application technology of ultrasonic testing.
In the years after World War I, both active sonar and passive sonar have been further developed. Britain and the United States mainly develop active sonar, which uses high frequency to keep it away from the ship noise frequency band and is not disturbed by the ship noise. For example, Langevin's sonar frequency is 38kHz, and the subsequent sonar frequencies are mostly 10 kHz ~ 30 kHz, and because of the high frequency, it can form a strong directivity. Germany was defeated at this time. According to the provisions of the Treaty of Versailles, it is not allowed to build submarines, but only small-tonnage warships. Their attention is focused on the development of the listened sound system. The German cruiser "Prince Eugen" is equipped with an array of 60 hydrophones on each side, which is well designed and has a great influence on the development of passive sonar in the future. By 1923, the echo detector jointly developed by Langevin and Chilovsky was exhibited at the 50th anniversary exhibition of the French Physical Society. At that time, about 3000 warships were equipped with different types of underwater acoustic equipment. 1937 appeared a temperature depth meter, which can quickly measure and calculate the change of sound velocity with depth in seawater, thus mastering the conditions of sound propagation and laying the foundation for the further development of sonar.
Sonar, as an underwater acoustic weapon, was fully developed in the Second World War and several years after the war. During this period, the range of sonar is increasing and the ability to distinguish targets is improving. Various types of sonar have appeared, from the giant sonar on the nuclear submarine to the guided sonar on the torpedo head. In order to use sonar in World War II, the United States concentrated on studying the influence of sound velocity distribution on sound propagation, and the United States and the Soviet Union independently found that it was caused by hydrological distribution. Ocean passage ",sound waves will not collide with the sea surface and seabed, but can travel a long distance." During World War II, the warring sides lost more than 1000 submarines, most of which were discovered by sonar. After World War II, the United States and the Soviet Union conducted an arms race, and underwater acoustic weapons were one of the important contents. With the rapid development of information theory and digital processing technology and the appearance of nuclear submarines and nuclear missiles, tactical acoustic detection of submarine close surveillance has developed into strategic acoustic detection of submarine long-distance surveillance in the ocean. In order to increase the detection distance and reduce the use frequency of sonar, so as to reduce the absorption and reception of the ocean; In order to maintain strong directivity, the number of hydrophones will be increased and installed into sonar arrays according to certain spatial distribution; In order to reduce the interference of propeller noise, sonar is often installed at the bottom of the bow, but the stern direction becomes a blind spot that sonar can't search. Therefore, a variable depth sonar is developed to drag the sonar in the seawater at the stern, and its depth can be adjusted, so that the sonar is not affected by bad sea conditions. In addition, the length of the transducer array needs to be increased, but the length of the ship is limited, so a long cable is towed behind the ship, and hundreds of transducers are installed to form a towed line array with a length of several hundred meters, which can be placed in a deep water layer with a depth of one kilometer for long-distance detection; In order to quickly search for submarines in a certain sea area, the method of helicopter dropping sonar buoys has also been developed, as shown in Figure 3-8. Anti-submarine aircraft can carry more than 80 sonar buoys. After the buoy is placed on the sea surface, it can be controlled by computer, which can monitor more than 30 sonar buoys at the same time and search the sea area quickly and widely.
After the disintegration of the Soviet Union and the disappearance of the confrontation between the two great powers, sonar gradually turned to the research of shallow sea exploration and marine development and application. The marine acoustic tomography technology has been developed, which can observe the marine phenomena in the range of 200 ~ 300 kilometers and treat the ocean as a human body for perspective and tomography. Recently, the acoustic temperature measurement of ocean climate has been developed to measure the sound speed of ocean passage, and according to the relationship between sound speed and seawater temperature, the temperature on ocean passage can be calculated, and the temperature rise data caused by the greenhouse effect of carbon dioxide can be obtained, so as to solve the important problems of human environmental protection.
Now sonar has developed by leaps and bounds. The range of modern sonar has increased hundreds of times, and the directional accuracy can reach a fraction of a degree, including electronic computers and very complex large-scale integrated circuits. The transducer of modern nuclear submarine sonar station is several meters in diameter and weighs more than ten tons, and the power consumption is equivalent to that of a small city. At present, in addition to ship-borne sonar, huge sonar transducer arrays are fixed in ports, important straits and main waterways. For submarines, this is a tight encirclement of sonar weaving.
In addition, anti-detection technology has also developed rapidly. Such as noise blocking technology that interferes with sonar work, stealth technology that reduces echo reflection, and false targets that interfere with sonar judgment. These are called electronic countermeasures in modern military terminology.
Interestingly, sonar is not a patent of human beings. Many animals have their own "sonar". Bats emit 10-20 ultrasonic pulses per second with their throats and receive echoes with their ears. With this "active sonar", they can detect tiny insects and wire obstacles with a thickness of 0. 1 mm ... moths and other insects also have "passive sonar", which can clearly hear the ultrasonic waves of bats 40 meters away, so they often avoid attacks. But some bats can use high-frequency ultrasound or low-frequency ultrasound that insects can't hear, so the hit rate of catching insects is still very high. It seems that animals are also engaged in "sonar warfare" like humans! Marine mammals such as dolphins and whales have "underwater sonar", which can generate very definite signals to explore food and communicate with each other.
Dolphin sonar has high sensitivity. It can find a metal wire with a diameter of 0.2 mm and a nylon rope with a diameter of 1mm several meters away, distinguish two signals with a time difference of 200μs, find fish schools hundreds of meters away, and walk through a pool full of bamboo poles flexibly and quickly blindfolded without touching them. Dolphin sonar has a strong "target recognition" ability, which can not only identify different fish and distinguish different materials such as brass, aluminum, bakelite and plastic, but also distinguish the echo of its own voice from the sound waves played back by the person who recorded its voice. The anti-jamming ability of dolphin sonar is also amazing. If there is noise interference, it will increase the call intensity over the noise so that its judgment will not be affected. And dolphin sonar also has the ability to express feelings. It has been proved that dolphins are animals with "language", and their "dialogue" is carried out through their sonar system. In particular, among the four remaining freshwater dolphins in the world, the most precious baiji in the middle and lower reaches of the Yangtze River in China has a clear "division of labor" in its sonar system, which is used for positioning, communication and alarm, and has a special function of phase modulation through frequency modulation.
Many kinds of whales use sound to detect and communicate, the frequency is much lower than that of dolphins, and the range is much farther. Other marine mammals, such as seals and sea lions, also send out sonar signals for detection.
Animals that have lived in the depths of the extremely dark ocean all their lives have to use sonar and other means to search for prey and avoid attacks. The performance of their sonar is far beyond the capabilities of modern human technology. Solving these mysteries of animal sonar has always been an important research topic of modern sonar technology.
Like the development of many technologies, the demand of society and the progress of technology promote the development of sonar technology.
The "shipwreck in the ice sea" incident prompted the birth of the echo detector. 191April 14, the British luxury passenger ship Titanic sank after colliding with an iceberg in the North Atlantic on its maiden voyage to the United States. The biggest shipwreck in history caused a great shock, prompting scientists to study the detection and location of icebergs. British scientist L.F. Sun Guohao applied for two patents five days and 1 month after the sinking of the ship, using sound waves to detect obstacles in air and water, and proposed using directional emission transducer, but it did not continue to work hard to realize his patent. 19 13, American scientist R·A· Fessenden applied for a number of patents for underwater detection, and made the first echo detector by using the moving-coil transducer designed by himself. 1965438+In April 2004, he successfully detected an iceberg 2 nautical miles (3.7 kilometers) away with the sound wave of 500- 1000 Hz emitted by this equipment.
Then, World War I broke out in 19 14, which greatly promoted the development of underwater acoustic positioning directional weapons. During the First World War, German submarines launched the "Infinite Submarine War", which was invincible for a while, posing a great threat to the maritime transportation of the allies and other countries, and almost interrupted transatlantic transportation. The allies and other countries were very angry and successively developed underwater acoustic equipment to detect underwater submarines. At that time, many famous scientists took part in this work. C. Chilovsky, a young electrical engineer in Russia, started the development of underwater acoustic detection equipment under the influence of the shipwreck in the ice sea very early. After the beginning of World War I, he recovered from illness in the mountains of Switzerland and felt the importance of anti-submarine warfare, so he turned his research direction to using high-frequency sound waves to deal with submarines. The idea of echo detection. His suggestion was adopted by the French government in February 19 15, and put into practice by the famous French physicist Professor Langevin. Langevin and Chilovsky decided to use high-frequency ultrasound. They use mica electrostatic transducer, put mica sheet in two electrodes, apply AC voltage to emit sound waves, and use carbon particle microphone as receiving transducer. With such simple equipment, the intercropping propagation experiments on both sides of the Seine River were successful at the end of 19 15 and the beginning of 19 16, and two kilometers of unidirectional propagation was realized. The news of their success spread to Britain, and Britain also set up a team to develop echo detectors.
In order to increase the detection distance, it is necessary to improve the transmission intensity and reception sensitivity. They use the piezoelectric effect discovered in 1880 ~ 188 1 year to generate and receive ultrasonic waves, but this piezoelectric effect is still very weak. At that time, a high-power electron tube high-frequency amplifier was invented in the field of electronics, which was just used to amplify the piezoelectric effect. The remaining problem is to find a timely single crystal with piezoelectric effect.
1917 10/in June, langevin finally persuaded an optician to give away the timely single crystal exhibit with a diameter of about10 inch that he had treasured for many years, cut off the wafer from it, made it into a timely piezoelectric receiving transducer, and then matched it with a mica electrostatic transmitting transducer to complete the project. Later, it was used to replace mica to complete 8 km one-way signal transmission.
After learning of Langevin's success, the British searched everywhere for large crystals. After all the crystal exhibits in geological museum, England, they went to the French crystal optician. They found a large number of crystals from the warehouse and made echo detectors. After listening to the introduction of Langevin's success by the British and French delegations, American scientists also strengthened their research work in this field.
During this period, people also developed passive sonar, which can determine their position by listening to the noise of enemy ships. The earliest passive sonar only had two receivers, which were heard through the stethoscope carried on the human head. In order to determine the distance accurately, a linear array with multiple hydrophones on each side was later developed. By rotating the linear array, the position of enemy ships can be judged by ears.
Regrettably, until the end of World War I, they did not make further achievements. Ultrasonic echo detection succeeded too late to show its great power in the First World War. However, the outstanding achievements of Langevin and his colleagues pioneered the application technology of ultrasonic testing.
In the years after World War I, both active sonar and passive sonar have been further developed. Britain and the United States mainly develop active sonar, which uses high frequency to keep it away from the ship noise frequency band and is not disturbed by the ship noise. For example, Langevin's sonar frequency is 38kHZ, and the subsequent sonar frequencies are mostly 10 ~ 30 kHz, and because of the high frequency, it can form a strong directivity. Germany was defeated at this time. According to the provisions of the Treaty of Versailles, it is not allowed to build submarines, but only small-tonnage warships. Their attention is focused on the development of the listened sound system. The German cruiser "Prince Eugen" is equipped with an array of 60 hydrophones on each side, which is well designed and has a great influence on the development of passive sonar in the future. By 1923, the echo detector jointly developed by Langevin and Chilovsky was exhibited at the 50th anniversary exhibition of the French Physical Society. At that time, about 3000 warships were equipped with different types of underwater acoustic equipment. 1937 appeared a temperature depth meter, which can quickly measure and calculate the change of sound velocity with depth in seawater, thus mastering the conditions of sound propagation and laying the foundation for the further development of sonar.
Sonar, as an underwater acoustic weapon, was fully developed in the Second World War and several years after the war. During this period, the range of sonar is increasing and the ability to distinguish targets is improving. Various types of sonar have appeared, from the giant sonar on the nuclear submarine to the guided sonar on the torpedo head. In order to use sonar in World War II, the United States concentrated on studying the influence of sound velocity distribution on sound propagation, and the United States and the Soviet Union independently found that it was caused by hydrological distribution. Ocean passage ",sound waves will not collide with the sea surface and seabed, but can travel a long distance." During World War II, the warring sides lost more than 1000 submarines, most of which were discovered by sonar. After World War II, the United States and the Soviet Union conducted an arms race, and underwater acoustic weapons were one of the important contents. With the rapid development of information theory and digital processing technology and the appearance of nuclear submarines and nuclear missiles, tactical acoustic detection of submarine close surveillance has developed into strategic acoustic detection of submarine long-distance surveillance in the ocean. In order to increase the detection distance and reduce the use frequency of sonar, so as to reduce the absorption and reception of the ocean; In order to maintain strong directivity, the number of hydrophones will be increased and installed into sonar arrays according to certain spatial distribution; In order to reduce the interference of propeller noise, sonar is often installed at the bottom of the bow, but the stern direction becomes a blind spot that sonar can't search. Therefore, a variable depth sonar is developed to drag the sonar in the seawater at the stern, and its depth can be adjusted, so that the sonar is not affected by bad sea conditions. In addition, the length of the transducer array needs to be increased, but the length of the ship is limited, so a long cable is towed behind the ship, and hundreds of transducers are installed to form a towed line array with a length of several hundred meters, which can be placed in a deep water layer with a depth of one kilometer for long-distance detection; In order to quickly search for submarines in a certain sea area, the method of helicopter dropping sonar buoys has also been developed, as shown in Figure 3-8. Anti-submarine aircraft can carry more than 80 sonar buoys. After the buoy is placed on the sea surface, it can be controlled by computer, which can monitor more than 30 sonar buoys at the same time and search the sea area quickly and widely.
After the disintegration of the Soviet Union and the disappearance of the confrontation between the two great powers, sonar gradually turned to the research of shallow sea exploration and marine development and application. The marine acoustic tomography technology has been developed, which can observe the marine phenomena in the range of 200 ~ 300 kilometers and treat the ocean as a human body for perspective and tomography. Recently, the acoustic temperature measurement of ocean climate has been developed to measure the sound speed of ocean passage, and according to the relationship between sound speed and seawater temperature, the temperature on ocean passage can be calculated, and the temperature rise data caused by the greenhouse effect of carbon dioxide can be obtained, so as to solve the important problems of human environmental protection.
Now sonar has developed by leaps and bounds. The range of modern sonar has increased hundreds of times, and the directional accuracy can reach a fraction of a degree, including electronic computers and very complex large-scale integrated circuits. The transducer of modern nuclear submarine sonar station is several meters in diameter and weighs more than ten tons, and the power consumption is equivalent to that of a small city. At present, in addition to ship-borne sonar, huge sonar transducer arrays are fixed in ports, important straits and main waterways. For submarines, this is a tight encirclement of sonar weaving.
In addition, anti-detection technology has also developed rapidly. Such as noise blocking technology that interferes with sonar work, stealth technology that reduces echo reflection, and false targets that interfere with sonar judgment. These are called electronic countermeasures in modern military terminology.
Interestingly, sonar is not a patent of human beings. Many animals have their own "sonar". Bats emit 10-20 ultrasonic pulses per second with their throats and receive echoes with their ears. With this "active sonar", they can detect tiny insects and wire obstacles with a thickness of 0. 1 mm ... moths and other insects also have "passive sonar", which can clearly hear the ultrasonic waves of bats 40 meters away, so they often avoid attacks. But some bats can use high-frequency ultrasound or low-frequency ultrasound that insects can't hear, so the hit rate of catching insects is still very high. It seems that animals are also engaged in "sonar warfare" like humans! Marine mammals such as dolphins and whales have "underwater sonar", which can generate very definite signals to explore food and communicate with each other.
Dolphin sonar has a high sensitivity. It can find a metal wire with a diameter of 0.2 mm and a nylon rope with a diameter of 1 mm several meters away, can distinguish two signals with a time difference of 200 burs, can find fish schools hundreds of meters away, and can walk through a pool full of bamboo poles flexibly and quickly blindfolded without touching. Dolphin sonar has a strong "target recognition" ability, which can not only identify different fish and distinguish different materials such as brass, aluminum, bakelite and plastic, but also distinguish the echo of its own voice from the sound waves played back by the person who recorded its voice. The anti-jamming ability of dolphin sonar is also amazing. If there is noise interference, it will increase the call intensity over the noise so that its judgment will not be affected. And dolphin sonar also has the ability to express feelings. It has been proved that dolphins are animals with "language", and their "dialogue" is carried out through their sonar system. In particular, among the four remaining freshwater dolphins in the world, the most precious baiji in the middle and lower reaches of the Yangtze River in China has a clear "division of labor" in its sonar system, which is used for positioning, communication and alarm, and has a special function of phase modulation through frequency modulation.
Many kinds of whales use sound to detect and communicate, the frequency is much lower than that of dolphins, and the range is much farther. Other marine mammals, such as seals and sea lions, also send out sonar signals for detection.
Animals that have lived in the depths of the extremely dark ocean all their lives have to use sonar and other means to search for prey and avoid attacks. The performance of their sonar is far beyond the capabilities of modern human technology. Solving these mysteries of animal sonar has always been an important research topic of modern sonar technology.
I don't know what the paper is. I can only help you with this matter. If you organize well, you will probably finish a paper.