Starting from Leonardo da Vinci's notes
As far back as A.D. 1490, a famous Italian artist and engineer named Da Vinci wrote in his notes: "If you stop the boat, put the closed end of a long pipe into the water and put the open end to your ear, you can hear the boat in the distance." This shows that hundreds of years ago, people realized that sound waves can be used to detect underwater objects. The audiometric tube described by Leonardo da Vinci is the prototype of modern passive sonar. It does not emit sound waves, but only monitors the acoustic signals emitted by underwater targets.
However, the performance of Leonardo da Vinci listening tube is not ideal: the orientation of underwater objects cannot be determined and the sensitivity is very low.
/kloc-In the late 20th century, the invention of telephone provided sonar with a high-sensitivity underwater acoustic receiver-carbon particle microphone.
The first practical application of underwater acoustics can be traced back to the early 20th century. At that time, with the development of navigation, large-tonnage ships appeared. The beacon and audible alarm of the original navigation system (such as steam fog signal, electric fog signal, fog clock, fog gun, etc.). ) is not suitable, especially in bad weather conditions such as rain, snowfall, windy or dense fog. Thus, the world's first underwater navigation system was born.
The navigation system consists of an underwater navigation clock and a carbon particle microphone. The giant underwater navigation clock, together with the fog signal, is set near the coastal lighthouse or on the beacon ship; The clock is filled with compressed air, which can drive the air hammer to ring the clock, thus automatically sending out acoustic signals in the water. The carbon particle microphone is installed in the watertight cover near the inner wall of the ship plate under the two baits at the bow; They convert the received bell signals into electrical signals, and send them to the two earphones of the telephone receiver in the face room through wires. The listener can roughly judge the position of the ship relative to the beacon according to the strength of the bell signals heard from the two receivers. If we further measure the time difference between the arrival of the fog horn from the beacon and the underwater navigation clock, we can determine how far the ship is from the beacon. The range of this navigation system can generally reach 16 km.
Up to 19 12, 35 underwater navigation clocks 135 have been installed all over the world, and some ships have installed receivers.
However, this navigation method and the radio navigation method invented later can only determine the relative position of the ship in the channel and avoid some reefs and shoals that have been discovered, while for other silent obstacles lurking in the water (such as icebergs, only one tenth of them are often exposed to the sea and most of them are hidden underwater), the ship becomes a "blind man". So j, a tragedy is inevitable.
191April 14, a new British cruise ship "Giant" with a tonnage of over 40,000 tons was sailing in the south of Newfoundland, Canada. There is a communication ship not far ahead of the giant. This communication ship once reported to the Giant, and now they are crossing a floating iceberg area. However, the operator of "Giant" was busy sending the private telegram of the rich old man, but he didn't receive the report.
At 23: 40, two lookouts on the front mast suddenly found a huge iceberg in front of the ship. The shift supervisor immediately ordered the left rudder to turn fully, but it was too late. The sharp edges and corners of the iceberg tore a big hole in the hull below the waterline. Ruthless sea water rushed into the ship's surface and the ship sank rapidly. By the time the two cruise ships rushed to the scene of the accident, the "giant" had sunk to the bottom of the sea for two hours. As a result, only 705 people were rescued and 1503 passengers were killed.
This was the biggest shipwreck in the world at that time, which caused a global shock. How can we avoid similar accidents? Many scientists are thinking.
Five days later, an Englishman named Richardson put forward the suggestion of echolocation with air sound. A month later, he proposed a similar underwater acoustic echolocation scheme, which is the first active sonar scheme in the world. The so-called active sonar is an underwater acoustic device, which emits sound waves into the water by itself and achieves various detection purposes (such as positioning) according to the echoes of objects in the water. Unfortunately, Richardson didn't realize his plan, because at that time, he couldn't make equipment that could emit sound waves in a given direction underwater.
19 13 years, American Fessenden developed a new type of dynamic vibrator. This kind of vibrator can directionally transmit and receive sound waves in water, and its structure is similar to the commonly used moving-coil speaker or microphone. In this way, icebergs 2 nautical miles away were quickly detected. Fessenden's vibrator was originally developed for underwater acoustic communication. After the key is connected, you can send and receive information according to Morse telegraph code. It is said that it was installed on American submarines during World War I, so that submarines could communicate with each other underwater. Its improved vibrator has been used until 1950.
Sonar and anti-submarine
History has repeatedly proved that "necessity" is the mother of invention. The urgent need of underwater anti-submarine warfare has promoted the rapid development of sonar technology.
1965438+In July 2004, World War I broke out. During the war, Germany launched an "unrestricted submarine war" and sank a large number of warships and merchant ships of the Allies by using the newly invented U-submarine. For example, a U-shaped submarine torpedoed three armored cruisers in just 75 minutes. The task of detecting underwater submarines is imminent! The Allies immediately launched an attack on Xu.
More manpower and material resources are needed to study the detection methods and equipment. Magnetic, optical and thermal methods have been tried, and the effect is good.
The practice of ignoring powder proves that the most effective method is acoustic method. As a result, various sonar systems came out.
In France, the famous physicist Ron Wan Zhi cooperated with the young Russian electrical engineer Chilovsky and conducted many experiments with the electrostatic emitter and carbon particle microphone placed at the concave focus. Finally, at 19 16, the echo of the seabed and the echo of the armored plate placed 200 meters away were received.
Later, Langevin turned to study the piezoelectric effect of the time, and successfully developed the time-steel sandwich ultrasonic transducer. Langevin transducer has high working frequency and strong directivity. Its improved version has been used to this day. In addition, Langevin also used a newly developed vacuum tube amplifier in his experiment, which may be the first application of electronic technology in underwater acoustics. In this way, the echo of an underwater submarine is received for the first time at 19 18, and the detection distance can sometimes reach 1500m.
Shortly after the end of World War I, a new type of ship navigation equipment-echo sounder was born. In fact, it is a by-product of people's development of echo positioning system for seabed exploration. Since then, due to the development of electronic technology and the improvement of underwater acoustic transducer performance, especially the in-depth understanding of the propagation law of sound waves in seawater, sonar technology has been continuously improved.
The outbreak of World War II opened a new era of sonar development. Since then, a series of new active and passive sonar have come out. The ships of the participating countries are equipped with sonar that can be used for combat.
1945, the British submarine "Adventurer" set a record: it attacked a German submarine that was also underwater based on the information detected by sonar. Since then, sonar, as an important eye and ear for underwater observation, has been increasingly consolidated.
Advance by leaps and bounds after the war
After World War II, sonar technology developed very rapidly. The main reasons are as follows: firstly, nuclear-powered submarines with missile weapons appeared in the 1950s, which put forward higher requirements for sonar performance; Second, the rapid development of electronic technology after the war prepared conditions for the development of sonar technology.
The maximum diving speed of nuclear submarines is generally around 25 nautical miles per hour (some of them exceed 30 nautical miles), which is several times faster than diesel-powered submarines; The average dive depth can reach about 450, which is much higher than that of diesel-powered submarines. Endurance1.2 ~ 200,000/200,000 nautical miles, and it can sail around the world continuously for two or three months, making diesel-electric submarines "look at the ocean and sigh"; But also can launch long-range missiles underwater to attack ships or land facilities of Laos. This requires greatly improving the detection distance and search speed of sonar, and effectively improving the reliability and continuity of sonar work.
Modern submarines are equipped with sonar systems with different uses, occupying a lot of space, and its value is the most expensive of all electronic equipment on board. The sonar system of surface ships is even bigger. A ship-borne active sonar, model AN/SQS-53 (improved), came out in 1960s. This sonar has 50 electronic cabinets, and there are 37 after improvement. All the equipment occupies about 16 meters at the bow, which fully occupies four decks.
Moreover, some countries also vigorously develop fixed sonar systems installed on the seashore or seabed, as well as airborne sonar carried by anti-submarine aircraft, and use communication satellites and large electronic computers to collect, transmit and process all kinds of detection data, forming a so-called "trinity" three-dimensional submarine detection system at sea, seabed and air.
The important development of sonar technology after the war is also highlighted in its rapid popularization in civil use. In addition to the traditional application in echo sounding, sonar technology is also widely used in underwater engineering facilities, marine research and marine development (including fish exploration and seabed resources exploration, etc.). ), and looking for the wreckage of the submarine shipwreck.
Culture uses sonar to explore the secrets of the ocean.