A system, apparatus, and method for processing substrates using acoustic energy. In one aspect, the invention can be a system for processing flat articles including a support for supporting the flat article and an acoustic energy treatment apparatus. The acoustic energy treatment apparatus may include a support arm and a plurality of transducer assemblies coupled thereto. The transducer assemblies may include a housing with a transducer coupled thereto, and the housings of the transducer assemblies may be arranged in an end-to-end manner. A trough may also be included that extends along at least a portion of a length of the transducer assemblies. The trough may serve as a reservoir that upon being filled and overflowed with a liquid allows the liquid to fluidly couple the transducer assemblies to the flat article.