A Study on Active Noise Control in 3-Dimensional Space. Active Acoustic Power Control Using Acoustic Nodal Points.

An active acoustic power control method for three-dimensional space was investigated both theoretically and experimentally. This paper focuses on the typical case of a single primary and multiple secondary point sources, and methods of minimizing the power output using the exisiting Filtered-X LMS algorithm are presented. Suitable arrangements of the sources and microphone are proposed on the basis of theoretical estimations. The authors call this the acoustic nodal point method. The power reducing performance was verified by applying the method to the noise radiating from a duct opening. Considerable noise reduction was achieved both at the error microphone and in the whole area around the noise source.