Listen to the noise of the forest: you distinguish the rustle of leaves, the sighs of the pine forest, muffled murmur of the oak grove. The rustle is heard only in the deciduous forest of leaves in the wind rub against each other, creating a forest noise.

Listen to the noise of the forest: you distinguish the rustle of leaves, the sighs of the pine forest, muffled murmur of the oak grove

Noise is a chaotic oscillations of different physical nature, are complex temporal and spectral structure. Originally, the word referred only to the noise and the sound was perceived as a set of aperiodic sounds of varying intensity and frequency, but in modern science it was extended to other types of waves (radio, electricity).

On the spectrum of noise divided into stationary and non-stationary, and the nature of the spectrum for broadband noise with a continuous spectrum width of more than 1 octave; tonal noise in the spectrum which are expressed by tone. Expressed tone is considered, if one-third octave frequency bands is greater than the other by at least 10 dB.

By the nature of occurrence of noise is divided into: mechanical, aerodynamic, hydraulic. Up to certain categories of noise include: White Noise is stationary noise, spectral components which are uniformly distributed over a range of frequencies involved; color noise is some types of noise signals that have a specific color, based on the analogy between the spectral density of the random nature of the signal and the spectra of different colors of visible light; Pink Noise (in the building acoustics), which changes the sound pressure level in octave frequency band.

For example, consider the noise of the forest. When the wind is incident on a thin branch on petiole or needles, the obstacles on the sides there are small air vortices. They move forward, one by one, and cause vibrations in the air; our ears perceive these vibrations as a forest noise. Forest noise is higher, the thinner the obstacle; why noise deciduous forest is different from conifers. The noise generated by a single twig or needles, barely audible: but from the confluence of many such noise turns louder noise of the forest.

Noise not only the forest: grass, too, makes a noise when the wind. You can hear the noise if the lie on the dried grass, consisting of stems: you hear a high-pitched whistling. All the familiar noise of the telephone wire has the same cause.

To measure the noise characteristics of the used sound level meters, frequency analyzers, correlators, and others. The noise level is most often measured in decibels.