Abstract: An apparatus for focussing vibrational energy upon a target volume within a surrounding contiguous medium imparts high intensity energy upon the target volume from low level energy sources. A plurality of standing compression waves are established within the medium along corresponding longitudinal axes between opposing pairs of coordinated transducers. The target volume is located at the common intersection of the axes of the standing compression waves. Opposing pairs of transducers are positioned from each other at a distance equal to an integer multiple of half wavelengths of the corresponding standing wave therebetween. The phase angle of each standing compression wave is regulated so as to cause each wave to be at its maximum intensity (amplitude) within the target volume at the point of common intersection with the other standing waves.