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we will be able to on the basis of the mathematical data reported here that process of changes of this size has character flat, the wave extending in this or that party with a speed and, or superpositions of such waves.

Here we will make the essential assumption: let's consider and depression so small that is admissible to neglect in a (2 members proportional () 2, () 3..., and to replace (the 2nd linear ratio

Wave surfaces can be any form. In the elementary cases they have a form of the plane or the sphere. Respectively the wave in these cases is called flat or. In a flat wave wave surfaces represent a set of the planes parallel each other, in a wave — a set of concentric spheres.

where v – the speed of a wave, T – the period of fluctuations. Wavelength can be determined also as distance between the closest points of the environment fluctuating with the difference of phases equal 2P. Having replaced in the ratio (T through 1/(– the frequency of fluctuations), we will receive

As it is known from thermodynamics, there is a function of density of this mass of gas (or liquids) and its temperatures. Temperature in the changes at compression and depression. Heat conductivity of gases and liquids is very small therefore it is possible to consider as a first approximation that at distribution of a sound process of compression and depression of each part of gas or liquid happens adiabatically, i.e. without noticeable heat exchange to the next parts. In thermodynamics is shown that in this case (if it is possible to neglect internal friction and some other phenomena temperature is unambiguous function of density and therefore, pressure also.

Thus, shift, speed, deformation and tension in the form of the waves connected definitely among themselves having the same speed and an identical of distribution.

Let's consider a case when the flat wave extends along an axis x. Then all points of the environment, position of balance of the have identical coordinate x (but various values of coordinates of y and z), fluctuate in an identical phase.

Between the receiver and a wall the source of sound vibrations with a frequency – 100 Hz is located. The line drawn via the receiver and a source is normal to a wall which moves to a source along this line from v=7 of m/s. Speed of a sound is 340 m/s. Whether emergence of an acoustic beating is possible.