ACTIVE CONTROL OF SOURCE SOUND POWER RADIATION IN UNIFORM-FLOW

Many suggested applications of active noise control involve the presen ce of a background air flow such as in ventilation ducts, exhaust stac ks and the radiation from turbofan engines. This paper is a theoretica l study aimed at assessing the effect of a uniform flow on the ability of simple sources actively to control free field sound power radiatio n. In particular, the minimum sound power radiated by two point volume velocity sources situated in an unbounded uniform fluid which moves w ith a uniform steady velocity is determined. Also the maximum sound po wer that can be absorbed by a point volume velocity source from an inc ident plane wave is determined. (C) 1998 Academic Press Limited.