Adaptive frequency domain identification for ANC systems using non-stationary signals

The problem of identification of secondary path in active noise control applications is dealt with fundamentally using time-domain adaptive filters. The use of adaptive frequency domain subband identification as an alternative has some significant advantages which are overlooked in such applications. In this paper two different delayless subband adaptive algorithms for identification of an unknown secondary path in an ANC framework are utilized and compared. Despite of reduced computational complexity and increase convergence rate this approach allows us to use non-stationary audio signals as the excitation input to avoid injection of annoying white noise. For this purpose two non-stationary music and speech signals are used for identification. The performances of the algorithms are measured in terms of minimum mean square error and convergence speed. The results are also compared to a fullband algorithm for the same scenario. The proposed delayless algorithms have a closed loop structure with DFT filterbanks as the analysis filter. To eliminate the delay in the signal path two different weights transformation schemes are compared

Recent Technological Advances in Spatial Active Noise Control Systems

This article provides a broad overview of the recent advances in the field of active noise control techniques to reduce unwanted noise over a certain spatial region of interest. Thanks to commercial and technological advances in local active noise control systems extending the size of the quiet zone seems to be a crucial step to developing the next generation of active control systems for a more personalized and quieter audio product. In this review article, the advances over the past decade the in design and development of spatial active noise control techniques to enlarge the controlled sound zone is reviewed. The focus is specifically on the adaptive control techniques and the methods proposed in the frequency domain to control the sound field. The study has paid specific attention to the most important performance measures in designing a spatial active noise control system such as convergence rate, stability and robustness of the algorithm, the size of the quiet zone and how it can be enlarged by configuring the loudspeaker and microphone array geometries. Finally, the authors will discuss the current and future challenges that should be overcome to improve the effectiveness of the recently proposed methods to expand the silence zone

Developing an IIR Robust Adaptive Algorithm in the Modified Filtered-x RLS Form for Active Noise and Vibration Control Systems

In this paper, a robust adaptive algorithm for active noise and vibration control applications is proposed and the robust stability of the algorithm is analyzed using a combination of the small gain theorem and Popov's hyper-stability theorem. The algorithm is developed based on the so-called Filtered-x RLS algorithm in the modified form. In design and analysis of the algorithm, it is assumed that the estimated model of the secondary path is associated with a set of uncertainties of additive structure; and sufficient conditions for stability of the algorithm are derived. In fact, by introducing a stabilizing filter, the aim is to design this filter in a way that the achieved sufficient conditions for robust stability are satisfied. The employed method is to transform the proposed control structure to an equivalent output error identification problem, and then formulate the governing adaptive algorithm in a way that is representable as a feedback control problem. In view of this approach, sufficient conditions for robust stability of the adaptive algorithm will be equivalent to find the conditions for the stability of the established feedback control system. The technique applied here to this end is established on the energy conservation relation that is valid for the general data models in adaptive filters