ACTIVE CONTROL OF ENVIRONMENTAL NOISE, IV: PRACTICAL EXTENSIONS TO ECAS THEORY

Abstract The basic Electronically Controlled Acoustic Shadow (ECAS) model in Paper I [1] (Wright and Vuksanovic 1996 Journal of Sound and Vibration 190,[rm] 565–585), considered the sound cancellation from a flat (2D), in-phase primary source, radiating in free field (no reflecting surfaces) and in a stationary propagating fluid (no wind), using monopole (omnidirection) cancellers. In Paper II [2] (Wright and Vuksanovic 1997 Journal of Sound and Vibration 202,[rm] 313–359), the theory was extended to high frequency non-compact acoustic sources, where the acoustic wavelength is small compared to the source size. Paper III [3] (Wright and Vuksanovic 1999 Journal of Sound and Vibration 220,[rm] 469–496) considered the implementation of ECAS theory into practice. This paper considers the following practical extensions to the basic ECAS model: (a) out-of-phase primary sources; (b) three-dimensional primary sources; (c) ground reflection; (d) directional secondary sources and (e) wind effect.