Active control of environmental noise, III: Implementation of theory into practice

In paper I [1] a theory for generating electronically controlled acoustic shadows for environmental noise reduction was considered. In paper II [2] the theory was extended to complex high frequency sound from non compact sources. Finally paper IV [10] considers the practical applications of the theory. These studies show that deep shadows are theoretically possible. This paper considers the implementation of the theory into a practical multichannel free-field control system and its basic performance. Providing certain stability conditions are met, deep shadows > 60 dB are generated at the microphones, limited only by the ambient noise of the laboratory.