Sound in the usual sense is represented by elastic waves propagating in a solid, liquid and gaseous medium.
The latter, in particular, includes ordinary air, the speed of wave propagation in which is most often understood as the speed of sound.
Sound and its distribution
The first attempts to understand the nature of soundWere made more than two thousand years ago. In the writings of the ancient Greek scientists Ptolemy and Aristotle, the correct assumptions are made that sound is generated by body vibrations. Moreover, Aristotle argued that the speed of sound is measurable and finite. Of course, in ancient Greece there were no technical possibilities for any precise measurements, so the speed of sound was measured relatively accurately only in the seventeenth century. To do this, a method was used to compare the time between the detection of a flash from a shot and the time through which a sound came to the observer. As a result of numerous experiments, scientists came to the conclusion that sound propagates in the air at a speed of 350 to 400 meters per second.
Researchers also found that the value ofThe speed of propagation of sound waves in a given medium depends directly on the density and temperature of this medium. So, the thinner the air, the slower the sound moves through it. In addition, the speed of sound is higher the higher the temperature of the medium. To date, it is commonly believed that the speed of propagation of sound waves in air under normal conditions (at sea level at 0 ° C) is 331 meters per second.
In real life, the speed of sound is significantParameter in aviation, but at those heights where planes usually fly, the characteristics of the environment are very different from normal ones. That is why the aviation uses a universal concept, which is called the Mach number, named after the Austrian physicist Ernst Mach. This number is the speed of the object divided by the local speed of sound. Obviously, the lower the speed of sound in a medium with specific parameters, the greater the Mach number, even if the speed of the object itself does not change.
The practical application of this number is connected withThe fact that the motion at a speed that is higher than the speed of sound is significantly different from the displacement at subsonic speeds. Basically, this is due to the change in the aerodynamics of the aircraft, the deterioration of its controllability, the heating of the hull, and also with the resistance of the waves. These effects are observed only when the Mach number exceeds unity, that is, the object overcomes the sound barrier. At the moment, there are formulas that allow us to calculate the speed of sound for various air parameters, and, consequently, calculate the Mach number for different conditions.