[Design and methodology in environmental acoustics]

On the basis of many experiments of urban acoustics carried out in the canton of Geneva, the authors come to the conclusion that the normative values cannot be applied when the estimate of discomfort level is concerned. They must be applied to prevent the risk of auditive acuteness loss. In order to establish discomfort, it is necessary to use methods to measure and analyse the results which are suitable for each condition, and to take into account the acoustic charge, the noise dynamics, the acoustic spectrum and the socio-economic environment of the people concerned. The conception has been accepted by Court of Justice in Geneva, which is now legally accepted: one may consider a uncomfortable any increase of 4-6 dB(A) of the acoustic level, as compared to the previous situation or to the background noise. The ability to differentiate between two stimuli is based on the physiological mechanisms of hearing.