Active control of narrowband acoustic noise of unknown frequency using a phase-locked loop

Abstract

An adaptive feedforward technique for active control of narrowband acoustic noise of unknown frequency is presented. A phase-locked loop is used to determine the fundamental frequency of the periodic component of the primary noise. Adaptive control of the residual noise is achieved with a least mean square method. Real time implementation is facilitated with an efficient recursive technique that is used to update the controller gains at each time step. Significant noise cancellation is demonstrated in physical experiments, which include additive broadband noise.