Living in the world of different waves, one is constantly experiencing the impact of sound.Sound vibrations - is not just a phenomenon accompanying him everywhere, but also a source of pleasure, but also a powerful information tool.Performing a variety of functions, the sound is able to warn of the danger, pleasure, become a means of communication.We are delighted to listen to the birds singing, nice music, engage in conversation with others.
Sound vibrations are important not only for humans but also for animals that use sound to survive.
By nature, a sound mechanical elastic waves, which are able to spread in solids in liquids, gases.Sound sources Sound vibrations cause vibration (mechanical oscillations), which is often invisible eye.To the sound source can be attributed physical bodies carrying vibrations per second (trembling or vibration) with a frequency of once 16-20000.Sound vibrations can cause solids (string, the Earth's crust), gas (air jet), liquid (sea waves).
Among the characteristics of the sound is assumed to specify two parameters: the tone - the frequency of sound vibrations;volume - the amplitude of the sound wave.The unit of volume is considered to be 1 Bel (it was named after one of the inventor of the telephone - Alexander Graham Bell).Almost one bel is not used, it is more convenient to use decibels, equal to one-tenth of Bel.To have a clear idea of the dimension of the volume to be taken into account that the 10 dB - whisper it;20-30 dB correspond to the normal noise in the living room;50 dB - is the average call volume;with the power noise of 80 dB truck engine is running;physiological pain threshold in humans occurs at 130 dB;180 dB can lead to rupture of the eardrum.
Considering the sound waves of different frequency, high-frequency waves to carry the birds singing, a low sound may include the sound of the engine of the truck.With the whole spectrum of properties and characteristics that are different waves of different nature, the sound waves are widely used in various fields.Properties of the liquid to carry out the sound being actively used in the exploration of the deep sea.All known echo, for example, used to determine distances in echolocation.A striking example can be called natural sonar of bats.
special type of ultrasound acoustic vibrations is highly effective tool in the hands of physicians and other researchers.These vibrations are the waves with frequencies of 000 Hz 20.This type of oscillation has a number of unique properties.Passing through the water, causing it to boil ultrasound (cavitation) with the occurrence of water hammer.Using ultrasound elements can detach from the surface of the metal crush the solids.Ultrasound allows mixing of fluids that normally do not mix, such as oil-based emulsion.Ultrasound allows the saponification of fats.This principle lies in the device of washing machines.Property produce crushing effect of ultrasound has been used in the ultrasonic soldering iron.
special kind of vibrations up to 16 Hz is called infrasound.It is known that this frequency fluctuations could have a painful impact on the human body.At frequencies of 4-8 Hz is felt the vibration of internal organs, in the frequency of 12Hz stimulates seasick.
Sources of infrasound can become the machinery with large surfaces, which make the mechanical vibrations of low frequency (mechanical origin) or flows of liquids and gases with turbulent properties (hydrodynamic or aerodynamic origin).
