4 ret'iew ts presented on t/re results of pret'ious research, using experimental modelling and field measurement, qf the insertion loss produced hy T-. Y-and arrow-profile noise barriers. ,4 numerical model is discussed which enables tire ware field in the region of a barrier with a complex profile and surface cot'er to he determined. An brtegral equationJormulation of the problem is soh'ed us#rg the boundao" element approach. Spectra of insertion loss Jor T-. Y-and arrow-profile barriers calculated using ttre model are discussed. Results for the mean insertion loss orer a range of receirer positions for a broad-hand source are also presented. It is concluded that for harriers with reflecting surfaces the changes in #Tsertion loss for different profiles can be described using the concept of path difference. The intro~hwtion of absorbing upper surfaces produces a significant increase in insertion loss. br most conditions the Y-and arrow-profiles perform less efficiently than the T-profile. Tire marked increase b7 barrier efficiency when a rerv thin narrow cap is added to a t'ertical wall which has been reported by other" workers was not obsert'ed.