Hybrid and Pseudo-Cascaded Active Noise Control Applied to Headphones
Creators: name: Rivera Benois, Piero Iared
Publisher: name: Universitätsbibliothek der HSU / UniBwH
Year: 2020
Subjects: subject: Active noise cancelling
subject: Active noise control
subject: Hybrid control
subject: Pseudo-cascaded control
subject: Headphone
subject: 600 Technik

description: The subject of this dissertation is the active control of acoustical noise by means of headphones. The contribution to the research field lies on three novel control structures and the optimization of their parameters. These control structures combine simultaneously the three classical control schemes, namely the feedforward, the minimum variance and the internal model control schemes, into one system. This without requiring additional microphones or loudspeakers. The optimization of the controller parameters is achieved in two stages. First, the minimum variance and the internal model controllers are co-optimized subject to the stability, performance, and controller gain constraints developed in this work. Second, based on their parameters and the novel control structure to be used, the feedforward controller is optimized. This can be done once for a fixed controller implementation, by following a Wiener controller derivation. Alternatively, the optimization can be done continuously over time based on the implementation of an adaptive controller. For achieving this goal the Modified Normalized Filtered-x LMS algorithm is integrated together with the novel control structures, such that a minimum of memory and computational resources is required. The fixed controllers are evaluated by means of simulations of an ANC headphones prototype subject to an ipsilateral free-field excitation. From the results it is concluded that, if the impulse response of the feedforward controller is as long as the one of the primary path, then the performance of the novel control structure is the same as the one of a classical feedforward scheme. However, if the impulse response of the feedforward controller is shorter than the one of the primary path, then the minimum variance and internal model controllers effectively extend its impulse response, such that it approximates the one of a longer controller. Thus, the novel control structures achieve a better performance. The adaptive feedforward controller is evaluated by means of an ANC Headphones prototype under ipsilateral and contralateral stochastic noise excitation. It is found that, under ipsilateral excitation the results achieved in the simulations could be corroborated. However, it is also found that the adaptation algorithms of the control structures are subject to some deterioration, if the impulse response of the modelled systems are not sufficiently long. Under a contralateral excitation the novel control structures showed to be subject to a dominant additive noise introduced by the feedforward controller. Nevertheless, it is also found that the performance of the minimum variance and internal model controllers combined together is resilient to the contralateral excitation. Hence, if the problem of the feedforward controller can be solved, the increase in performance of the novel structures can be achieved also under these circumstances.