text: In UIT, ultrasonic waves are produced by an electro-mechanical ultrasonic transducer, and applied to a workpiece.  An acoustically tuned resonator bar is caused to vibrate by energizing it with a magnetostrictive or Piezoelectric ultrasonic transducer.  The energy generated from these high frequency impulses is imparted to the treated surface through the contact of specially designed steel pins. These transfer pins are free to move axially between the resonant body and the treated surface.
  When the tool, made up of the ultrasonic transducer, pins and other components, comes into contact with the work piece it acoustically couples with the work piece, creating harmonic resonance. This harmonic resonance is performed at a carefully calibrated frequency, to which metals respond very favorably, resulting in compressive residual stress, stress relief and grain structure improvements.
  Depending on the desired effects of treatment a combination of different frequencies and displacement amplitude is applied. Depending on the tool and the Original Equipment Manufacturer, these frequencies range between 15 and 55 kHz, with the displacement amplitude of the resonant body of between .