Sound is a physical phenomenon that is the propagation of mechanical vibrations in the form of elastic waves in a solid, liquid or gaseous medium. In the narrow sense, sound means these vibrations, considered in connection with how they are perceived by the senses of animals.
Like any wave, sound is characterized by amplitude and frequency. Amplitude refers to the loudness of the sound. Frequency determines tone, pitch (see pitch). An ordinary person is able to hear sound vibrations in the frequency range from 16-20 Hz to 15-20 kHz. Sound below the human hearing range is called infrasound; higher: up to 1 GHz - ultrasound, from 1 GHz - hypersound. The loudness of a sound depends in a complex way on the effective sound pressure, frequency and mode of vibration, and the pitch of sound depends not only on the frequency, but also on the magnitude of the sound pressure.
Among the audible sounds, phonetic, speech sounds and phonemes (of which oral speech is composed) and musical sounds (of which music consists) should be emphasized. Musical sounds contain not one, but several tones, and sometimes noise components in a wide frequency range.
The concept of sound
Sound waves in the air are alternating areas of compression and rarefaction.
Sound waves are an example of an oscillatory process. Any oscillation is associated with a violation of the equilibrium state of the system and is expressed in the deviation of its characteristics from equilibrium values with a subsequent return to the initial value. For sound vibrations, such a characteristic is the pressure at a point in the medium, and its deviation is the sound pressure.
If you make a sharp displacement of the particles of the elastic medium in one place, for example, with the help of a piston, then the pressure will increase in this place. Due to the elastic bonds of particles, the pressure is transferred to neighboring particles, which, in turn, act on the next ones, and the area of increased pressure seems to move in an elastic medium. The area of increased pressure is followed by an area of reduced pressure, and thus a series of alternating areas of compression and rarefaction are formed, propagating in the medium in the form of a wave. In this case, each particle of the elastic medium will oscillate.
In liquid and gaseous media, where there are no significant fluctuations in density, acoustic waves have a longitudinal character, that is, the direction of vibration of the particles coincides with the direction of movement of the wave. In solids, in addition to longitudinal deformations, elastic shear deformations also arise, causing the excitation of transverse (shear) waves; in this case, the particles oscillate perpendicular to the direction of wave propagation (transverse wave).
The speed of propagation of longitudinal waves is much higher than the speed of propagation of shear waves.
In philosophy, psychology and ecology of means of communication, sound is studied in connection with its effect on perception and thinking (we are talking, for example, about acoustic space as a space created by the impact of electronic means of communication).