A theoretical method for determination of multiple scattering of an acoustical wave by a grating of elastic obstacles is presented. The main advantages of the method are: The same formulation works for finite arbitrary gratings as well as for infinite plane gratings; and the calculation of the properties of the whole grating is decoupled from the calculation of the scattering properties of the individual components set in free field. Some results on compliant tube gratings (plane gratings and a parabolic reflector) are shown and compared to experiments.