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This paper presents the design, fabrication, and testing of a piezoelectric parametric frequency increased generator for harvesting low-frequency non-periodic vibrations. The generator incorporates a bulk piezoelectric ceramic machined using ultrafast laser ablation. The electromechanical transducer is designed as a clamped-clamped spiral beam in order to decrease the stiffness within a limited footprint. An internal mechanism up-converts the ambient vibration frequency to a higher internal operation frequency in order to achieve better electromechanical coupling and efficiency. To gain maximum power output, the optimum width and thickness values of a spiral up-conversion unit are computed via multi-physics finite-element analysis simulations. The fabricated device generated a peak power of 100 μW and an average power of 3.25 μW from an input acceleration of 9.8 m/s2 at 10 Hz. The device operates over a frequency range of 24 Hz. The internal volume of the generator is 1.2 cm3.