Source and Sensor Placement Optimisation for Spatial Active Noise Control

Sammanfattning

Spatial Active noise control (ANC) aims to manipulate sound fields within target regions through active control methods, with applications including noise cancellation and high-fidelity audio reproduction. The placement of secondary sources and sensors has a significant impact on system performance; however, traditional approaches optimise these placements independently, resulting in suboptimal results. This thesis addresses the joint source and sensor placement optimisation problem in spatial ANC systems. The challenge lies in formulating an effective cost function that simultaneously optimises secondary source placement for sound field synthesis and sensor placement for accurate spatial interpolation, while maintaining reasonable computational complexity. A novel joint cost function formulation was developed that explicitly incorporates interpolation error alongside synthesis error by comparing interpolated field estimates against the true desired field across the entire control zone. This approach addresses fundamental limitations in existing methods, including clustering behaviour and convergence issues, by properly accounting for estimation uncertainty inherent in limited sensor measurements. A comprehensive simulation environment was implemented to evaluate four placement algorithms: Random (baseline), Regular (geometric), Greedy (optimisationbased), and Matching Pursuit (signal processing-based). The algorithms were systematically compared using normalised mean square error and computational efficiency metrics across multiple resolution configurations. Results demonstrate that optimisation-based approaches provide meaningful performance improvements over simple placement strategies, with the Greedy algorithm achieving the best acoustic performance. However, significant computational trade-offs were revealed, with optimisation methods requiring substantially longer execution times. The novel cost function formulation successfully resolved convergence issues and demonstrated superior robustness across varying acoustic conditions.