Living in the world of different waves, people constantlyexperiencing the influence of sound. Sound vibrations are not just a phenomenon that accompanies it everywhere, but also a source of pleasure, as well as a powerful information tool. Performing a variety of functions, the sound is able to warn about danger, to give pleasure, to become a means of communication. We are delighted to listen to the birds singing, pleasant music, enter into conversation with other people.
Sound vibrations are important not only for humans, but also for animals that use sound to survive.
By nature, sound ismechanical elastic waves that are able to propagate in solids, in liquids, in gases. Sources of sound sound vibrations cause vibration (mechanical vibration), which is often invisible to the eye. Sound sources can include physical bodies oscillating per second (shaking or vibrating) with a frequency of 16–20000 times. Sound vibrations can cause solids (string, earth's crust), gaseous (stream of air), liquid (sea waves).
Among the characteristics of sound, it is customary to single out twoParameter: timbre - frequency of sound vibrations; volume - the amplitude of the sound wave. The unit of sound volume is considered to be 1 Bel (it was named after one of the inventors of the phone, 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 loudness dimension, you should take into account that 10 dB is a whisper; 20–30 dB correspond to normal noise in a residential area; 50 dB is a medium volume talk; with a noise power of 80 dB, the engine of the truck runs; physiological pain threshold in humans occurs at 130 dB; 180 dB can rupture the eardrum.
Considering the sound vibrations of differentfrequencies, the high-frequency waves include the singing of birds, the low sounds include the sound of a truck engine. Possessing the whole range of properties and characteristics that distinguish waves of various natures, sound waves have found wide application in various spheres. The property of the fluid to conduct sound is actively used in the exploration of the deep sea. The well-known echo, for example, is used to determine distances in echolocation. A striking example of natural sonar can be called bats.
A special kind of sound vibrations isUltrasound, a very effective tool in the hands of physicians and other researchers. Such oscillations include waves with frequencies beyond 20,000 Hz. This type of oscillation has a number of unique properties. Passing through the water, the ultrasound causes it to boil (cavitation) with the appearance of a water hammer. With the help of ultrasound it is possible to tear off elements from the surface of the metal, crushing solid bodies. Ultrasound allows you to mix liquids that under normal conditions do not mix, for example, emulsions with an oil base. Ultrasound allows the saponification of fats. This principle lies in the design of washing machines. The ability of ultrasound to produce crushing effect has found application in ultrasonic soldering irons.
A special kind of vibrations up to 16 Hz received the nameinfrasound It is known that fluctuations in this frequency can have a painful effect on the human body. At frequencies of 4-8 Hz, vibration of internal organs is felt, the frequency of 12 Hz provokes an attack of seasickness.
Sources of infrasound can be machines andmechanisms with large surfaces that perform low-frequency mechanical oscillations (mechanical origin) or fluids and gases with turbulent properties (hydrodynamic or aerodynamic origin).
