/ / Sound waves: concept and features

Sound waves: concept and features

The world that surrounds us is safe.call the world of sounds, because around us are constantly heard voices, music, birds chirping, the sound of the wind. Sound waves help people communicate, receive information about the world around them. For animals, sounds are no less important. From the point of view of physics, sounds are mechanical vibrations that propagate in an elastic medium: water, air, a solid body, and so on. Human ears are able to hear sound when sound frequencies are in the range of 16 to 20,000 Hz. Oscillations with higher or lower frequencies are not audible to humans.

Science acoustics is engaged in solving a variety ofissues, including issues related to the features and properties of hearing. The subject of the study of physiological acoustics is directly the organ of hearing, its structure, action and device. Architectural acoustics deals with the study of how sound waves propagate in a room, examines the influence of the shape and size of a room on a sound, and studies the properties of materials from the currents of propagation and suppression of sounds. Musical acoustics is engaged in the study of musical instruments, examines the conditions of the best sound of a particular instrument.

Physical acoustics studies sound vibrations themselves, sound waves, recently it also began to embrace vibrations that lie beyond the capabilities of the human auditory system.

Basic Acoustics

The appearance of sound is due to mechanicalfluctuations of elastic bodies and environments. Air is a sound conductor. This was proved by the experience of Robert Boyle. If you put any sounding body under the bell of the air pump, then as the air is pumped out from under the bell, the sound will become weaker. When the air under the bell ends, the sound stops altogether.

During vibrations, the body alternately createsvacuum in the layer of air adjacent to its surface, then compresses this layer. As a result, the propagation of waves in the airspace begins with vibrations of the air layer near the surface of the body.

As sound waves travelin space, sound attenuation is observed, which is associated with certain irreversible processes. The point is that part of the energy transferred by the sound wave is absorbed by the medium.

Absorption coefficient is a quantitywhich is equal to the ratio of the sound energy absorbed by the medium to the energy that has entered the medium. The absorption coefficient is influenced by the internal friction or viscosity of the medium, its thermal conductivity, the density of the medium and the speed of wave propagation.

Propagating in the environment, the wave somedaycomes to its border. After this boundary, another medium begins, which consists of other particles and in which there is another speed of sound. On this border is a reflection of sound. In this case, the rarefaction of the particles turns into a condensation, and the condensation turns into a vacuum.

This effect occurs because fluctuations,which the wave brings to the boundary of the medium, are transmitted to particles of another medium and become the source of a new wave. The secondary wave will propagate not only in the second environment, but also in the one from where it originally came. This will be the reflected sound wave.

Partial passage occurs at the boundary of media.sound in the second environment and partial absorption of sound. The fraction of the reflected energy will depend on the ratio of the densities of the media, as well as on the state of the interface. For example, the reflection of a sound wave propagating in air from a liquid surface or a solid body occurs almost completely. Sound waves propagating in a solid will almost completely be reflected at the boundary with the air.

With the phenomenon of reflection is directly relatedthe occurrence of echo. The essence of this phenomenon is that the sound comes from the source to a certain obstacle that will become the boundary of the media, and is reflected from it, returning to the place of the origin of the wave.