Ultrasonic subsurface cleaning

Apparatus for cleaning marine fouling material from a submerged surface, comprising, in combination:

• a submersible housing moveable along a submerged surface to be cleaned and having an opening for apposition with said surface;
• and first and second transducer assemblies carried by said housing and having radiating surfaces for directing beams of ultrasonic energy to intersect at a zone of cavitation at said submerged surface,
• said assemblies comprising transducers operable at different frequencies and at levels of excitation just below the onset of cavitation at their radiating surfaces, so that said beams combine and result in cavitation and non-linear interaction in said zone, to give sum and difference frequencies;
• and
• means mounting said assemblies in pairs spaced along said housing, each mounting means comprising an arcuate member slideable transversely of said housing, means pivoting said assemblies to said arcuate member at sites spaced therealong, and means clamping said member to said housing at a site between the sites of pivoting of said assemblies.