The noise barriers excess attenuation can differ under different meteorological conditions of outdoor sound propagation. The results of in situ measurements of excess attenuation of 5 different road traffic noise barriers are presented. The road traffic noise was measured on 10 different days for each barrier at distances 25 m, 50 m and 100 m from the barrier and at heights 2 m and 5 m over absorptive surface. The meteorological conditions were also measured during the noise measurements. A very wide variance of excess attenuation was measured both in L Aeq values and L A 90 values at each site. These differences cannot be explained by any prevailing single meteorological factor.

        Key words: meteorological conditions - Exces alternation