Sound radiation from a point force in circular motion

Abstract This paper is a theoretical study of sound radiation from a time-varying point force in accelerative motion, where the acceleration arises from steady rotation in a circle. The study is prompted by the question of whether such effects are significant in fan or helicopter rotor noise at subsonic tip speeds. Closed-form expressions are found for the overall radiation at a point in the far field, and for the radiated sound power, showing the acceleration effect as an additive term in each case. The effect of rotation on the broad-band far-field spectrum is demonstrated by a series expansion for rotational frequencies small compared with the radiated frequency.