1. What do noise and vibration mean?

Noise is when a set of sounds is perceived as annoying. It is therefore a subjective notion: the same sound can be considered useful, pleasant or annoying depending on who hears it, and when. However, when noise levels are very high, all sounds are perceived as annoying, and can even be dangerous.

Vibrations, on the other hand, are dynamic phenomena, i.e. in motion. The study of periodic motion and, more specifically, oscillatory motion, allows us to distinguish two modes of exposure to vibrations:

• vibrations transmitted to the hand-arm system by portable, rotating or percussive machines (grinders, chain saws, jackhammers, etc.), hand-guided machines (vibratory plates, etc.) or hand-held workpieces;

• vibrations transmitted to the whole body by mobile machines (forklifts, construction...