ABSTRACT

By using the concepts of non-radiating sources and wave-splitting, a theoretical framework for a general treatment of active noise control of sound is presented in this paper. An ideal noise control (i.e., total noise cancellation) is achieved if the out-going wave from the source region vanishes, or the sum of the noise and control sources forms a non-radiating source. To illustrate how these concepts can be utilized to control noise actively, several numerical examples are given for an infinite duct. Numerical results show that one can choose different arrangements for the control sources, e.g., control sources continuously distributed over the whole source region, control sources continuously distributed over some finite regions outside the noise source region, or isolated monopole/dipole sources located at the boundary of the source region. The ideas and results have also been generalized to the three-dimensional case. The present systematic approach gives new perspectives to the active noise control mechanism.