IMproved stable feedback anc system with dynamic secondary path modeling

This paper presents the development and DSP implementation of a stable ANC feedback system with online secondary path modelling, using the Normalized Filtered-X Least Mean Square with Noise Addition algorithm (NFXLMS-NA), for acoustic noise cancellation. In this paper, the feedforward and the feedback ANC systems are described briefly; the basic of the FXLMS algorithm and its structure is discussed and the new NFXLMS-NA algorithm is presented. The ANC system developed includes a conventional noise predictor, a primary adaptive filter, a subsystem for dynamic secondary path modelling and the addition of white noise signal in the FXLMS algorithm in a novel structure looking for stability into the system. The system was developed for cancelling quasi-periodic acoustic noise; some experimental results for narrowband signal are included in order to show the desirable feature (stability) of the system. Proposed system was implemented using a TMS320C30 evaluation module from TI. Finally, the paper includes the block diagram of the ANC system, the structure of the program used in the implementation and some photographs of the practical scheme and the equipment used in the tests.