2008 Volume 2 Issue 6 Pages 1296-1305
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 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 controlling has not been considered in conventional ANC. A new algorithm is proposed in this paper to address this issue. The algorithm calculates filters as a function of position by using a time-delay filter and a distance-attenuation coefficient, which are calculated from the position of the evaluation point. Computer simulations of acoustic characteristics in an anechoic chamber and an ordinary office are conducted. The results of these simulations demonstrate the effectiveness of the proposed algorithm.