The multi-input multi-output theorem (MINT) for causality problems reduction in active noise control

摘要

This paper deals with the causality constrain in active noise control of interior noise, namely it studies the possibility of reducing this problem in cases where it doesn't have a fundamental nature connected to true delays in the system, but is more related to the enclosures reverberation time. The MINT theorem can be used to show that, for such cases, if the number of reference signals is greater than the number of noise sources and if the number of secondary signals is greater than the number of error microphones, the causality problems can be greatly reduced. However, in some cases, the problem can becomes badly conditioned and without use from a practical viewpoint. This is of special importance for inversion of the pre-reference path, because the reference signal can receive a large amount of ambient noise. The article describes some computer simulations of such systems is small enclosures to evaluate to what extent this problem appears in practice. In addition, a MC-LSL algorithm is presented to solve the problms associated with the high correlation of the reference signals of these systems.