Electrodynamic Hammer vs. General Pneumatic Hammer

Pneumatic hammer system

The following research paper was discussed at the IEEE Workshop on Accelerated Stress Testing and Reliability. 
The Pneumatic Hammer System combines both vibration and shock waves in a continuous impact strokes. However, before generating the shock pulse, purely vibration wave is observed.
In the Electrodynamic Hammer System, the duration between each impact can be precisely controlled so that the phases of each hammer on a multiple hammer system can be manipulated individually.