Everyone knows that you can put your hand in a pond, move it in front and back and the waves will spread on the surface of the water. If I want to make a sound that everyone can hear in a room, I have to send similar waves through the air, which is like a sea. We are at the bottom of the atmosphere and we make waves in the air that surrounds us and when we do the sound waves travel, reach the ear of the listener and the increase and decrease in pressure cause the eardrum to vibrate and the listener to have that psychological reaction of: "I'm hearing a sound"
The sound is something that moves through the air, when the molecules collide in it and we notice that pressure. So, when we talk or something vibrates, what it does is actually alter the density of the air and change it periodically. There is a periodic fluctuation in the density of those air particles that are moving. The only place where we could not have sound waves is in the real void, where there is no particle that can carry those waves. The biggest void we can imagine is: Space.
The speed of sound refers to the speed of propagation of sound waves by a given medium and in known conditions of temperature. For example, the speed of sound in the air at 20 degrees Celsius, at 50% humidity and at sea level is 1 235 km / h or 343 m / s. However, in those same temperature conditions, the speed of sound in water is 4.5 times greater (approximately 5 735 km / h or 1,600 m / s). In general, the speed of sound travels faster the more solid the medium (solids - liquids - gases) and the higher the temperature (increases 0.6 m / s each degree centigrade).
Sound is a physical phenomenon that results from the disturbance of a medium. This disturbance generates a wave behavior, which causes it to propagate to reach the site where a receiver is located. This type of movement in which it is not the medium itself but some disturbance that is displaced is called a wave. There are many other types of waves, such as radio waves, light, heat radiation, waves on the surface of a lake, sunamis, seismic movements. When the wave takes place in a liquid or gaseous medium it is called an acoustic wave. When it is audible, it is called a sound wave.
In aviation, the sound barrier was considered as a limit of the speed at which it could be reached. This limit began to be reached when, thanks to the technical advances of the Second World War, the planes improved their speed a lot and began to have problems when flying at high speeds.
The sound barrier comes from the speed at which the sound moves, from 1,225 km / h to 15º Celsius which is called Mach 1. This way of naming it is to simplify since the speed of sound changes with temperature but the effects that occur at that speed are the same, that is, the air surrounding an aircraft flying to Mach 1 will experience the same properties although this Mach 1 is reached at 1,225km / h or 1,000km / h because it is at higher altitude and air be colder t supposes a barrier to cross it because when approaching to this speed the form in which the air flows around its surface changes and it becomes a compressible fluid giving rise to a greater resistance.
Currently, humanity has the technology to build aircraft capable of flying very fast. The Austrian physicist Ernst Mach, Mach number defined as the relationship between the speed of the object and the sound in the medium in which the object is.
So a military fighter flying at Mach 2, travels 2 times faster than the speed of sound. Some of these aircraft can reach Mach 6 The SR-71 Blackbird, the aircraft used during the Cold War, reaches 4,300 km / h. Since the X15 airplane tests reached 7,200 km / h, approximately 6 times faster than sound waves.
Soldiers are told not to exceed Mach 1 in cities and inhabited places because the plane exceeds the sound produced by itself, which generates a shock wave that can damage the human ear and break the windows of nearby buildings.
The first airplane that officially overcame the sound barrier flying over Mach 1 horizontally was the Bell X-1 prototype on October 14, 1947, which was a manned rocket that was launched from a modified B-29 bomber. A German pilot claims to have been the first, on April 9, 1945 during World War II aboard a Me-262. This plane was the first operational jet plane and came to fight in the last months of the war.
In a gas or a liquid, sound consists of compression waves. In solids, waves propagate through two different types of waves. A longitudinal wave is associated with compression and decompression in the direction of travel; it is the same process in gases and liquids, with an analogous compression wave in solids.
Only compression waves exist in gases and liquids. An additional type of wave, called transverse wave or rotational wave, occurs only in solids since only solids can withstand elastic deformations.
This is because the elastic deformation of the medium is perpendicular to the direction of travel of the wave. The direction of the deformed rotation is called the polarization of this type of wave. Generally, transverse waves occur as a pair of orthogonal polarizations. The compression speed of waves in a fluid is determined by the compressibility and density of the medium.
In solids, compression waves are analogous to those found in fluids, depending on the compressibility, density and additional factors of the transverse modulus of elasticity. The speed of the rotational waves, which occur only in solids, is determined only by the modulus of transverse elasticity and the density of the module.
