Harvesting ambient kinetic energy can power microsystems that cannot fit batteries large enough to sustain them across their operational life. Increasing the mechanical-to-electrical conversion efficiency of piezoelectric transducers (PZTs) is critical in this space. A good understanding of how PZTs behave and react to motion and electrical loads is therefore necessary. This is especially true when ambient sources are irregular, which are more prevalent than the periodic vibrations that literature often considers. This paper interprets and models PZTs with periodic and irregular sources and energy-harvesting loads. SPICE simulations show how electrical loads can affect PZT cantilever motion.