ACTIVE CONTROL OF SOURCE SOUND POWER RADIATION IN UNIFORM FLOW

Many suggested applications of active noise control involve the presence of a background air flow such as in ventilation ducts, exhaust stacks and the radiation from turbofan engines. This paper is a theoretical study aimed at assessing the effect of a uniform flow on the ability of simple sources actively to control free field sound power radiation. In particular, the minimum sound power radiated by two point volume velocity sources situated in an unbounded uniform fluid which moves with a uniform steady velocity is determined. Also the maximum sound power that can be absorbed by a point volume velocity source from an incident plane wave is determined.