Active control of environmental noise - III: Implementation of theory intopractice

In paper I [1] a theory for generating electronically controlled acoustic s hadows for environmental noise reduction was considered. In paper II [2] th e theory was extended to complex high frequency sound from non compact sour ces. Finally paper IV [10] considers the practical applications of the theo ry. These studies show that deep shadows are theoretically possible. This p aper considers the implementation of the theory into a practical multichann el free-field control system and its basic performance. Providing certain s tability conditions are met, deep shadows > 60 dB are generated at the micr ophones, limited only by the ambient noise of the laboratory. (C) 1999 Acad emic Press.