Active noise control systems offer a potential method of reducing the weight of passive acoustic treatment and, therefore, increasing vehicles’ fuel efficiency. These can be particularly cost-efficient if integrated with the entertainment system. A combined system is presented employing feedforward control of engine noise and feedback control of road noise, using a ‘modal’ error signal. Due to the dependence of the feedback system on the modal response of the vehicle cabin, and the influence of structural-acoustic coupling on this response, the effects of structural-acoustic coupling upon the performance of the active noise control strategies is investigated. An elemental model of structural-acoustic coupling is derived and used to simulate the change in performance of the active control systems as a result of coupling; the feedforward component is largely unaffected by structural-acoustic coupling, whilst the modal feedback performance is reduced from 11 to 8 dB attenuation in total acoustic potential energy, due to the shift in the frequency of the targeted acoustic mode. The simulation results are confirmed through experiments conducted in a structural-acoustic coupled enclosure.
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