Active Noise Control for a Moving Evaluation Point Using Transfer Function Interpolation

In active noise control (ANC), the transfer function of the error path (TFEP) changes when the evaluation point moves, and it causes a bad performance of noise control. In this study, a new method to identify TFEP at an arbitrary point is proposed. This method is based on the plane wave theory, and the impulse response of TFEP is derived analytically as a function of the position, using measured impulse responses at two points. Applying this method to update the compensation filter of the varying TFEP in a test tube, it is verified by the experiment that the noise can be suppressed significantly without divergence.