Sound vibrations. Practical use. Effects on humans

Living in a world of different waves, a person is constantly experiencing 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, sound can warn of danger, give pleasure, become a means of communication. We listen with delight to the singing of birds, pleasant music, we enter into conversation with other people.

Sound vibrations are important not only for humans, but also for animals that use sound to survive.

By its nature, sound is a mechanical elastic wave that can propagate in solids, liquids, gases. Sound sources sound vibrations cause vibration (mechanical oscillation), which is often unnoticeable to the eye. Sound sources include physical bodies that perform vibrations per second (trembling or vibration) with a frequency of 16-20,000 times. Sound vibrations can cause solid bodies (string, crust), gaseous (air stream), liquid (sea waves).

Among the characteristics of sound it is customary to distinguish two parameters: timbre is the frequency of sound vibrations; Loudness - the amplitude of the sound wave. The unit of loudness of sound is considered to be 1 Bel (it was named after one of the inventor 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 visual representation of the volume dimension, it should be taken into account that 10 dB is a whisper; 20-30 dB correspond to the usual noise in the living room; 50 dB is the average volume of the conversation; With a noise power of 80 dB running the truck's engine; The physiological pain threshold in humans occurs at 130 dB; 180 dB can lead to rupture of the eardrum.

Considering sound vibrations of different frequencies, singing birds refers to high-frequency waves, the sound of the motor of a truck can be referred to low sounds. Possessing the whole spectrum of properties and characteristics, with which waves of different nature are distinguished, sound waves have found wide application in various fields. The property of a liquid to carry out sound is actively used in exploration of the sea depths. Every known echo, for example, is used to determine distances in echolocation. A vivid example of natural echolocators can be called bats.

A special kind of sound vibration is ultrasound, a very effective tool in the hands of doctors and other researchers. Such oscillations include waves with frequencies over 20,000 Hz. This type of oscillation has a number of unique properties. Passing through the water, ultrasound causes it to boil (cavitation) with the occurrence of a hydraulic shock. With the help of ultrasound, it is possible to tear off elements from the surface of the metal, to crush solid bodies. Ultrasound makes it possible to mix liquids that are not normally mixed, for example, emulsions with an oil base. Ultrasound allows the saponification of fats. This principle lies in the arrangement of washing machines. The property of ultrasound to produce a crushing effect has found application in ultrasonic soldering irons.

A special kind of vibration up to 16 Hz was called infrasound. It is known that fluctuations of this frequency can have a painful effect on the human body. At frequencies of 4-8 Hz, vibration of the internal organs is felt, a frequency of 12 Hz provokes an attack of seasickness.

Sources of infrasound can be machines and mechanisms with large surfaces that perform mechanical vibrations of low frequency (mechanical origin) or flows of liquids and gases with turbulent properties (hydrodynamic or aerodynamic origin).