STUDY OF THE ACOUSTIC FEEDBACK PROBLEM OF ACTIVE NOISE-CONTROL BY USING THE L(1) AND L(2) VECTOR-SPACE OPTIMIZATION APPROACHES

This study attempts to explore the acoustic feedback problem that is f requently encountered in feedforward active noise control (ANC) struct ure from the standpoint of control theories. The analysis is carried o ut on the basis of the Youla's parametrization and the l(1)-norm and l (2)-norm vector space optimization. The ANC problem is formulated as a model matching procedure and is solved via linear programming in the dual vector space. These methods alleviate the problems caused by the nonminimum phase (NMP) zeros of the cancellation path. The ANC algorit hms are implemented by using a digital signal processor. Various types of noises were chosen for validating the developed algorithms. The pr oposed methods are also compared with the well-known filtered-u least- mean square (FULMS) method, The experimental results show that the aco ustic feedback problem significantly degrades the performance and stab ility of the ANC system regardless which method is used. Insights into the difficulties due to acoustic feedback are addressed along the lin e of control theories. (C) 1997 Acoustical Society of America.