Noise pollution in most European and mainly Greek towns, is a major environmental problem. The annoyance caused by environmental noise is great and the use of a reliable descriptor of noise is important. This paper attempts to evaluate the noise fluctuations at an observation point by introducing a probabilistic model for the system environment-noise.The proposed model considers environmental noise as a stochastic signal neglecting the identity of noise sources as well as all other physical factors of the system. Regression methods were used to fit fluctuating noise levels to a trigonometric series. The use of "power spectrum" linearizes the problem and simplifies the method of regression in searching for the best model. A correcting term of L dn is proposed and the use of the model makes the calculation of the above mentioned term simple.