Active noise control in ducts using adaptive digital filters

Billet, Laurent Ludovic Jerome (1992) Active noise control in ducts using adaptive digital filters. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The propagation of sound in a duct can be actively controlled by introducing a secondary source driven to cancel t he original sound wave produced by a primary source. In this study we compare for the first time in the same conditions three adaptive time domain algorithms currently used for the active control of noise in ducts : the LMS (Least Mean Square) algorithm, the LMS algorithm with feedback cancellation and the infinite impulse response LMS algorithm. Firstly we establish the theoretical basis necessary to calculate the optimal single channel controller. Secondly we study each algorithm through a practical realisation and through computer simulation using an appropriate electro-acoustic model of the real The infinite impulse response algorithm is found to be the most efficient one. Moreover we demonstrated that the imperfect frequency response of the transducers (microphone and loudspeakers) is responsible for most of the limitation of the active noise control system. experiment.

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