These reflexions are based on recent studies concerning industrial diseases caused by noise. All welfare and health control associations are more and more concerned about this problem, as diseases caused by noise are not only irreversible but still appear long after the phenomenon that provoked them. This study recalls what noise means, how it can be defined, how it can be measured with modern technics, what types of noises are or are not bearable, and what are the human reactions facing the various frequency levels. The study quotes a very full literature on the"noise"phenomenon and describes the method used to find out the source of noise on an old packing machine conceived before the noise standards were set up. The illustration refers to a mechanical group. The contributions different parts can have on the total level of noise are analysed. Vibrational analysis is used to determine the phase where the signals occur. High speed film analysis is used to measure the amplitude of the oscillations. The paper concludes with the results accompanied by illustrations which have been obtained from theoretical analysis.