We designed a wireless power transmission (WPT) system using airborne ultrasonic waves and measured the received power characteristics of the system. Ultrasonic WPT is evaluated from these characteristics. We support the future development of ultrasonic WPT by presenting the details of the components (generator, amplifier, transducer, rectifier) that make up this system, with a detailed discussion. It has also been shown that when multiple transducer-rectifier circuits (passive sources) are used at the receiver, they can be connected in parallel to add all the signals and efficiently supply power to the load. Finally, we discussed the potential of near-field WPT as well as vibration energy harvesting.