Abstract
In this paper, measurement methods of sound power levels for ducted fans were described. As measurement methods, "essentially free field method based on SHASE-S 110" were compared with "four kinds of sound intensity method". The sound intensity levels were measured at discrete points or measured by scanning. Moreover, measured surface of the sound intensity levels were sphere or box shape. As a result, the sound power levels for ducted fans were almost equal between essentially free field method and sound intensity methods.
