Acoustical scale model experiments carried out with building‐size barriers are described. The results of experiments conducted with the barrier in a free field and on a reflecting surface are presented. The free‐field measurements are compared to several theoretical models and discrepancies between the theoretical and experimental results are discussed. Also presented is a simple expression which relates the excess attentuation obtained with the barrier situated on the ground to that of the same barrier in the free field. This expression predicts excess attenuations which agree quite closely with those actually measured in the scale model experiments.