Active Noise Control Using Position of Evaluation Point

Active noise control (ANC) in a three-dimensional sound field ( e.g., in an office) is investigated in this paper. As the size of the controlled area generally depends on the wavelength of the target noise, it is difficult to control the noise throughout an entire room using ANC. Instead, a noise control method in the vicinity of a subject's head (referred to as around-head control) is investigated in this paper. To realize around-head control, an evaluation point that mimics head movement is required. However, movement of the evaluation point during control has not been considered in conventional ANC. The authors earlier proposed control using a filter map to solve this problem. In this method, the controlled space is subdivided into small grids, and a filter map is produced by storing and updating filters in each grid. A new method of updating the map is proposed in this paper, in which a reliability index is calculated and used. The effectiveness of the proposed method is shown by numerical simulations using acoustic properties measured in an anechoic chamber.