This research reports an acoustic wireless energy transmission system featuring high efficiency and robustness. The proposed energy transmission system is composed of a piezoelectric cantilever-based transmitter and receiver that are coupled using the forces of permanent magnets. Taking advantage of the strong coupling effect of magnet force, we can transfer mechanical energy wirelessly through mediums of the air and metal plate. The experimental studies show that the voltage transmission efficiencies reach 55.59% and 51.58% in cases of energy transfer through mediums of the air and the air-metal-air, respectively. In addition, the maximum power transmission reaches 42.73 mW at an operational frequency of 104.2 Hz. This wireless energy transmission system can be used for powering devices in enclosed, electrically shielded, and biomedical areas.