Definition of noise

NOISE

Objective definition:
It is the physical phenomenon of mechanical origin involving a (very slight) variation in pressure, in vibratory rate and or fluid density which spreads while gradually modifying the state of each element of the medium in question, thereby giving rise to a sound wave (the diffusion of the rings in water following disturbance of the surface provides a good representation of this phenomenon).

Subjective definition:
it is the sensation caused by this wave which is received by the ear and subsequently transmitted to the brain where it is deciphered. Among all the sound waves, only some can be detected by the ear: these are waves with a frequency of between 20 Hertz (Hz) and 20,000 Hz (20 kHz). Below 20 Hz, one speaks of infrasounds and above 20 kHz, one speaks of ultrasounds.

Noise is a vibration of the air which is characterised by its frequency (tonality), its intensity and its duration.