Active noise control using geometrical information of an evaluation point

Active noise control (ANC) in a three-dimensional sound field (e.g., in an office) is investigated in this paper. Since the size of the controlled area generally depends on the wavelength of the target noise, it is difficult to control the noise in a whole room using ANC. Instead, noise control method in the vicinity of a subject's head (referred to 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. Authors have proposed control with filter map in order to solve this problem. In this method, the controlled space is subdivided into small grids. A filter map is produced by storing and updating filters in each grid. A new method for updating the map is proposed in this paper. A reliability index is calculated and used in this updating method. The effectiveness of proposed method is shown by numerical simulations using acoustic properties measured in an anechoic chamber.