world that surrounds us, we can confidently call the world of sound, because around us the voices, the music, the chirping of birds, the sound of the wind.Sound waves help people communicate, get information about the world around them.For animal sounds are of equal importance.From the point of view of physics, the sounds are mechanical oscillations propagating in an elastic medium: water, air, solid, and so on.Human ears can hear the sound, when sound frequencies are in the range of from 16 to 20 000 Hz.Fluctuations with higher or lower frequencies are not audible to humans.
Science Acoustics is addressing a variety of issues, including issues related to the characteristics and properties of the hearing.The subject of the study of physiological acoustics is the organ of hearing itself, its structure, operation and device.Architectural acoustics deals with the study of how the sound waves in the room, considering the influence of the shape and size of the room to the sound, exploring the properties of materials with the current proliferation and suppression of sounds.Musical Acoustics deals with the study of musical instruments, explores the condition of the best sound of a particular instrument.
Physical Acoustics studies themselves sound waves, sound waves, lately it also became the cover fluctuations that are beyond the capabilities of the human auditory system.
Concepts acoustics
advent of sound caused by mechanical vibrations of elastic bodies and the media.Air is for the sound conductor.This is proved by the experience of Robert Boyle.If you put a body under a sounding bell of an air pump, then at least the pumping out of the air bell sound becomes weaker.When air under the bell end, the sound will stop altogether.
During oscillation body alternately creates a vacuum in the layer of air adjacent to the surface, then compresses the layer.As a result of the propagation of waves in the air space begins with the vibrations of the air layer near the surface of the body.
As soon as the sound waves travel in space, there is the sound attenuation, which is associated with certain irreversible processes.The idea is that some of the energy carried by the sound waves is absorbed by the medium.
the absorption coefficient is a quantity that is equal to the ratio of sound energy absorbed by the environment, to energy, which entered the environment.On the absorption coefficient affects the internal friction or viscosity of the medium, its thermal conductivity, density and speed of propagation.
propagating through medium wave ever comes to its limits.After this boundary starts other medium that consists of other particles and in which the different speed of sound.This border is carried out sound reflection.In this vacuum of particles converted into thickening and thickening - discharged.
This effect occurs because the vibrations that brings a wave to the border environment, transferred to another medium particles and become the source of a new wave.Second Wave will be distributed not only in the second medium, but also the one where it originally came from.This will be the reflected sound waves.
at the boundary there is a partial passage of sound into the second medium and the partial absorption of sound.The proportion of energy reflected will depend on the ratio of medium density, as well as the state of the interface.For example, the reflected sound wave propagating in the air or from the liquid surface of the solid is almost completely.Sound waves propagate in a solid, almost all will be reflected at the interface with air.
On reflection phenomenon is directly related to the emergence of the echo.The essence of this phenomenon is that the sound comes from a source to a certain obstacles, which will be the boundaries of the medium, and is reflected from it, returning to the place of occurrence of wave.
