Active control of the field scattered by the rigid wall of a semi-anechoic room—Simulations and full-scale off-line experiment

Abstract

This paper is dedicated to an experimental implementation of active anechoicity control illustrating previous theoretical work. The aim of this experimental is to cancel the pressure scattered by the single rigid wall of a semi-anechoic room, turning the latter into a fully anechoic one over a given frequency range. The proposed method is presented in two steps: estimation of the scattered pressure and its control. Two numerical simulations are presented in order to show the feasibility of the method. An experimental campaign is presented, where the active control system leads to a reduction of the field scattered by the rigid wall throughout a significant part of the measuring volume inside the room. Although these results are based on post-processing of measurements, and not real-time computation, they confirm the possibility to extend the frequency range of a small facility toward lower frequencies, by adding to its passive lining a set of ordinary sources and pressure microphones.