Active sound cancellation, as an important technique in noise control, requires an effective control algorithm to achieve its optimum performance. The objective of this project is to design the algorithm using feedback control theories which not only enhance the performance, but also reduce the installation cost. One of the difficulties facing the feedback design is the infinite-dimensional nature of the sound system. The novelty of this study is to use the closed-form transfer function to describe the dynamics of sound. The transfer function reveals many useful properties which are lost when a discretized model, such as the modal expansion, is used. The proposed study which seeks (a) to develop a time-domain recursive identification scheme can directly identify the dynamics of sound in ducats;(d) to develop the repetitive control system for harmonic noise cancellation; (c) to experimentally verify the performance of the repetitive control system; (d) to develop a broad-band active noise controller based on transfer function models; (e) to extend the result to sound cancellation of higher modes. The study will complement the research of microphones and loudspeakers used in active sound cancellation. Also, it provides a good case study of the feedback optimization of distributed parameter systems. Although only active sound control is considered, this study has potential applications to general vibration control.*** //
