Apparatus and method for cleaning/etching the surface of an article with sonic energy in the megahertz range which employ an anti-reflection mechanism within a recirculation tank. A tank having at least one side wall and a bottom structure holds a cleaning/etching liquid and a megasonic transducer is associated with the tank for projecting megasonic energy into the liquid. The anti-reflection mechanism is disposed within the tank in close association with the at least one sidewall or bottom structure of the tank to thereby minimize reflection of megasonic energy from the associated surface. Preferably, the megasonic transducer is associated with a first tank sidewall which opposes a second tank sidewall, and the anti-reflection mechanism is disposed adjacent the second tank sidewall. By way of example, the anti-reflection mechanism can comprise a stream of gas bubbles, a plurality of anechoic structures, or a combination of both gas bubbles and anechoic structures.