One of the most common types of telecommunications - telephone - lets you use electricity to transfer audio (human voice) over long distances.
Human speech is sound waves - waves. The emergence of sound is due to the mechanical vibrations of solids, air, liquids, and other media, perceived human ears. Movement, in which the body or particles are displaced from a position in one direction and then the other, called oscillations.
If you hold an elastic steel plate in a vise and take her to the free end of the side, and then release it, the album will make motions. Body performs one complete oscillation, if it is moved from its equilibrium position M to point A, then comes to the position B, and returns to the point M.
Vibrations transmitted to the steel plate adjacent to it the particles of air, which also begin to oscillate and transmit vibrations neighboring particles, and these, in turn, pass them on. As a result, the air produced and distributed in all directions at a speed of 332 m / s sound waves.
Sound vibrations are characterized by a period, frequency and amplitude.
The time in which is one complete oscillation is called the period. Period designated by the letter T and is measured in seconds (s).
The number of complete oscillations, is done in one second is called frequency. Frequency sound waves denoted by the letter f, and is measured in hertz (Hz). If, for example, one second is 500 complete oscillations, the frequency of these oscillations is equal to 500 Hz. One hertz equals one full swing, perfect for a second.
Oscillation frequency is measured in kilohertz (kHz) and megahertz (MHz):
1000 c = 1 kHz, 1000 kHz = 1 MHz = 1 million cps.
The higher the frequency, the less time.
Human ear, perceiving sounds, distinguishes them on the basic elements sound perception - height, strength and tone.
Pitch perception of sound is called, depending on the frequency of sound waves. The higher the frequency of sound waves, the greater the pitch. The human ear can perceive sound vibrations frequency of 20 to 20,000 Hz.