Chapter 1: Invited Addresses and Tutorials on Signals, Coding,
  Systems and Intelligent Techniques

Title: A system development method for global active noise control

Author(s): S.M. Potirakis, M. Rangoussi

Address: Department of Electronics, Technological Education Institute of Piraeus 250, Thivon str., GR-12244, Aigaleo-Athens, Greece | Department of Electronics, Technological Education Institute of Piraeus 250, Thivon str., GR-12244, Aigaleo-Athens, Greece

Reference: 12th International Workshop on Systems, Signals and Image Processing pp. 375 - 379

Abstract/Summary: Control or reduction of noise is a field of great practical interest, because noise affects all aspects of life and has a direct impact on human health. Active noise control is an area receiving a constantly growing research interest, as it constitutes the only practical solution for low frequency and/or non stationary noise components. This work focuses on global active noise control, where noise reduction is sought for large, open or near-free-field areas, like public access places or industrial production premises. The variety of noise sources and their spectral and time characteristics, the physics of sound wave propagation in large / open spaces, the non-stationary acoustic conditions due to movement of people and/or equipment are factors that render global (active) noise control a challenging research field. As the successful but small room oriented ANC solutions cannot be directly ported to the global case, we propose here a methodology for system design and development, aiming to address the problem globally, i.e., to combine passive noise control methods for mid-high and high frequency noise with active noise control for low frequencies. For the later, a polymorphic ANC structure is implemented, which dynamically switches among alternative control structures and related adaptive filtering algorithms, driven by psycho-acoustic and objective optimality criteria. The proposed approach exploits the Maximum Length Sequence, both for modelling / system identification purposes and for implementation of a 'soft microphones' noise measurement procedure. The steps of the proposed method are tested, verified and optimized in a real field global ANC system development project, including target areas both of large industrial and of free-field public character. Successful application of our stepwise procedure in this project shows that it is generic enough to cover a variety of target areas.

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