A method for processing flat articles with acoustical energy. The inventive system method can remove particles from both sides of a wafer more efficiently and effectively. In one aspect, the invention is a method for processing flat articles wherein a liquid is applied to both major surfaces of the flat article. A first transducer assembly is positioned adjacent to a first of the major surfaces of the flat article and a second member is positioned adjacent to a second of the major surfaces. The first transducer assembly generates and transmits acoustical energy to the first major surface of the flat article while the second member either: (1) reflects the acoustical energy generated by the first transducer assembly back to the second major surface of the flat article; and/or (2) generates and transmits acoustical energy to the second major surface of the flat article.