The sound in the conventional sense is the elastic waves propagating in the solid, liquid and gaseous environment.
The latter, in particular, applies to normal air, the speed of wave propagation in which most often meant by the speed of sound.
Sound and its propagation
The first attempts to understand the nature of sound occurrenceThey were made over two thousand years ago. In the writings of the ancient Greek scholars Aristotle and Ptolemy made the correct assumption that the sound generated by the vibrations of the body. Moreover, Aristotle argued that the speed of sound is measurable and finite quantity. Of course, in ancient Greece there was no technical possibilities for any accurate measurements, so the speed of sound was relatively accurately measured only in the seventeenth century. We used the method of comparison between the time of detection of the outbreak of the shot and the time after which the observer shot through sound. After numerous experiments, the researchers concluded that sound propagates in the air at a rate of 350 to 400 meters per second.
The researchers also found that the value ofvelocity of propagation of sound waves in a particular environment depends on the density and temperature of the medium. Thus, thinner than the air, the slower it moves sound. In addition, the sound velocity is higher, the higher the temperature of the medium. To date, it is assumed that the speed of propagation of sound waves in the air under normal conditions (at sea level at a temperature of 0? C) is equal to 331 meters per second.
In real life, the speed of sound is a significantparameter in the air, but at those altitudes where planes normally fly, environmental characteristics differ from normal. That is why the aircraft used universal concept, which is called the Mach number, named after the Austrian physicist Ernst Mach. This number represents the speed of the object divided by the local speed of sound. Obviously, the smaller the speed of sound in the medium with specific parameters, the greater Mach number, even if the velocity of the object will not change.
The practical application of this is due tothe fact that the motion at a speed that is higher than the speed of sound differs significantly from moving at subsonic speeds. Basically, this is due to the aerodynamics of the aircraft change, deteriorating its manageability, body heat, as well as resistance to waves. These effects are observed only when the Mach number is greater than one, ie, the object breaks the sound barrier. Currently there are formulas that allow to calculate the speed of sound in air or other parameters, and, consequently, to calculate the Mach number of different conditions.