A hybrid active noise control system
Wybrane pełne teksty z tego czasopisma
In this article a hybrid noise control system for active headsets is designed. It combines analoque and discrete feedback techniques. However, both of these contributing parts are analysedseparately, before they are combined in a common system. The design of analoque controller starts from identyfying continuos time system, choosing a proper contoller structure, and finding its initial parameters with the aid of the system frequency characteristics. Final parameters are orginally searched in an optimisation process with a cost function and appropriate constrains formulated. The contoller is then practically realised in electronic circuit with a switched capacitor filter. The dicrete controller requires in turn modelling of the discretised plant including analoque filters and convertes. Well known Internal Model Control structure is used with Filtered-x LMS algorithm. The same structure operates in the hybrid system, where modelling of the analoque closed loop is required. Features of such systems are analysed. Efficiency of the algorithms is verified on a prototype of the active headsets. A variety of noises is considered, both generated and real-life. The experiments confirm good cooperation of the analoque and discrete techniques. The former is responsible for attenuating random broadband noise components. The latter, however, contributes to the overall attenuation, reducing, deterministic components to the acoustic background. The main contribution of this atricle is thus: reported in details original design of analoque active noise control system, its combination with supervisory discrete controller, successful practical realisation and high attenuation level with possibilityto easily tune basic performance parameters, what makes the system flexible and efficient in terms of various working environments.
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