Almost from the very invention of airplanes and airships, it was decided to put them into service with the army. And already during the First World War they were a formidable force. And it was possible to defend against enemy aircraft only if its approach was noticed in advance. That is why special devices have been developed that can capture the sound of a flying plane or zeppelin, although they often look more like an "orchestra". These were military tubes.
Radars for detecting aircraft were invented on the eve of World War II, but before that special acoustic locators were used, more like huge musical instruments. The first listening devices were created at the end of the 19th century.
This was, for example, the invention of Professor Mayer, called the "topophone". The locator, invented in 1880, had the appearance of large "ears" that were attached to the body without taking up the arms. But Mayer's topophone had one significant drawback: you just have to stand with your back to the supposed direction of the sound source, as nothing will be heard.
But, it should be said that locators of a similar design have been improved and used after. The advantage of such devices was that they could be produced more in quantity, because they were much smaller and controlled by one operator. However, their quality still noticeably suffered in comparison with the "wiretaps" of large sizes.
Another inventor of the locator at the end of the 19th century was a certain Roar M. J. Bacon. His device was already much larger than a topophone and required several people to work. As a test, Bacon and his assistants tried to hear the sound of a flying balloon.
Those huge military tubes were first tested in France and Great Britain. Their design was quite unusual: they were two or more large horns, which were attached to a kind of "stethoscope". With their help, for example, British troops prevented zeppelin raids.
The development of military tubes was based on systems for detecting and determining the location of enemy raids. No electronics or radios were required - the locators were completely mechanical.
There were a huge number of forms and modifications of pre-radar listening devices. One of the most common during the First World War was a design in which several horns - most often there were three - were arranged in a row one above the other, and another, additional horn was on the right or left of the main configuration.
The central and lateral parts served to determine the direction of the approaching enemy attack. And with the help of the upper and lower horns, the operators determined the height at which the aircraft were located.
Thus, military tubes mechanically amplified the sound, and the position of the locator was adjusted according to it to adjust it to the direction with the maximum volume of aircraft noise. After that, simple calculations were made to establish the height and range of enemy aircraft.
However, despite the popularity of military tubes in the air defense calculations of many countries, the quality of their work left much to be desired - they were insensitive and could determine the localization of the enemy in the air only at a distance of several kilometers. And even the capabilities of the aviation of the First World War made it possible to overcome this path in just a few minutes.
Military engineers found a way out, who began to investigate locators of other shapes and sizes. This is how acoustic mirrors appeared in Great Britain - static structures made of concrete in the shape of a parabola. After the First World War, their number increased markedly along the entire coast of the eastern part of England. Most often, acoustic mirrors were in the form of huge plates, in rare cases, they were a concave wall.
Interesting fact: the diameter of the acoustic mirror reached 9 meters.
Military tubes and acoustic mirrors were actively modified in the interwar period, but they could no longer “keep up” with technical progress. Towards the end of the 1930s, a new generation of locators began to appear, such as the Alan Blumlein microphone, also called the "sound direction finder". According to Novate.ru, the device was powerful enough to reach a radius of 30 kilometers under certain conditions.
In addition, by the beginning of World War II, aircraft designers could already design aircraft capable of flying at speeds of at least 300 km / h, which made the operation of military tubes simply ineffective. And although they were still used in some places during the war years, the invention of radars capable of detecting the approach of enemy aircraft at a distance of up to 130 kilometers quickly replaced these obsolete devices.
Not only the locators had an original shape, the aviation itself sometimes acquired a very impressive appearance - 10 aircraft of the XX century, when looking at which it becomes clear where the stories about UFOs came from.