Les effets des bruits sur la vigilance en fonction de leurs caractéristiques physiques et psychophysiologiques

The effects of noise on behaviour during a long period can be classified as a function of their significance and of their physical characteristics. Among the non-significant noises, those which are short and unexpected determine an immediate disturbance followed by an improvement of vigilance for a certain lapse of time. In a monotonous situation, continuous noises can sometimes slightly improve the results during an initial period soon followed by a markedly reduced attention. This double effect is much more marked when the noise is intense and shrill. When noises constantly changing in their intensity and in their spectral composition constitute the working environment, the degrading effect is still earlier and more marked than in the case of a monotonous noise.

Music seems a more favourable condition for good vigilance and to be superior to the condition created by a monotonous noise. Speech gives very different results according to the subject's knowledge of the job.

One finds these opposite effects of noise (stimulation and distraction) in the analysis of the investigations regarding music in industry. The working environment and in particular the noise environment appear to influence the watching efficiency of the operator. The results obtained in the factories seem sometimes contradictory. A classification of noises probably allows one to make a more exact appreciation of the phenomena. We recall in the first instance the data from the literature concerning non-significant noises, then we describe the results that we have been able to obtain with significant noises, and finally we try to extract some useful recommendations for working conditions.