Optimization of the Active Control of Turboprop Cabin Noise

In this paper, a modified cost function is proposed in order to achieve themaximumnoise attenuation using a set of secondary sources for a harmonically excited sound field. The modified cost function drives the error signal to the optimally attenuated sound field instead of minimizing the squared pressure. Moreover, changing the value to which the error signals must be driven allows change of the control strategy from global to local. Themodified cost function requires theknowledge of the attenuated sound field,which is a condition that iswell suited to narrowbandnoises, as is the case of turboprops. A numerical example of the application of the cost function is carried out using a finite element model/boundary elementmodel of a real turboprop,with the goal ofminimizing the interior sound field in the cabin to about 17 m3. A maximum averaged attenuation of 7 dB at blade-passage frequencies is achieved using six secondary sources and six error sensors, and 11 dB around the head of a seated crew member if the control system is tuned to achieve local control.