• AFESOPWs exhibit an additional self-priming frequency that synergizes with the second high-amplitude frequency band, producing larger pressure amplitudes.
• Three high-amplitude frequency bands in waterjet pressure correspond to plunger pump excitation, shearing layer vortex, and bubble collapse.
• Self-priming of annulus fluid enhances cavitation, with cavitation cloud shedding frequency linearly related to cavitation number.
• Modulating pressure oscillation and cavitation shedding frequencies can improve peak pressure and cavitation erosion effectiveness.