Light velocity or a sound is constant, relatively counter or passing driving of the observer. 440 hertz, are a note of La of the first octave, we will allow amplitude = 1 centimeter. Acoustic speed = 330 meters per second / 440 hertz = 0,76 meter = 76 centimeters, it is a wavelength of a note of La. 1 second / 440 hertz = 0,0022 seconds, this time of the period of a wave of a note of La of the first octave. The acoustic speed is defined by measurement of time of passing the beginnings of the first amplitude from a sound source to the registrar, if a sound the ideal sinusoid, further measurements are complicated. But, really the sound consists of a set of the changing overtones, all the time is born initial amplitude, therefore hearing constantly records driving and the direction of a sound. The sound wave consists of the first shock half-cycle, with a set of harmonicas and overtones, and the second fading half-cycle. Better the first in which molecules of air are directed is perceived towards driving of a sound on 38 centimeters, with a run of each molecule = 1 centimeter. The second half-cycle fading in which molecules of air come back on 1 centimeter in the opposite direction, at half wave length = 38 centimeters, is reproduced more weakly. Let the observer move towards a sound source, will overtake, and then moves incidentally with a sound. The Doppler effect, at first towards, time shock will be shown, counter half-cycle will decrease, an overtone of a sound will be raised. When overtakes, a normal sound. Then, at passing driving with a sound, the shock half-cycle will become running away, its time will increase, an overtone of a sound will become the under. At rather small speeds of land transport, time of half-cycles is redistributed, and time of the entire period, a wavelength of a sound of La, practically does not change. On the main sound, the frequency of overtones which have no noticeable periods changes. And if the observer moves with a speed of 660 mete ... Читать далее