The output of an ultrasonic wave-driven nanogenerator (NG) has been found to depend on the excitation conditions and geometry. Incidence angle tests indicate that the effective area of an NG determines the amount of power that can be generated. The output power of an NG is also directly related to its distance from the ultrasonic source. A sinusoidal profile of the electrical output was observed when an NG was moved inside a long tube filled with water with the ultrasonic source located at one end. This is due to the oscillation of the wave intensity inside the tube as a function of the distance from the excitation source.