Active noise control at a virtual acoustic energy density sensor in a three-dimensional sound field

Abstract

A common problem in local active noise control is that the zone of quiet centered at the physical microphone is too small to extend to the desired location of attenuation, such as an observer’s ear. The physical microphone must therefore be placed at the desired location of attenuation, which is often inconvenient. Virtual microphones overcome this by shifting the zone of quiet away from the physical microphone to a desired location of attenuation, referred to as the virtual location. In an effort to extend the zone of quiet generated at the virtual location, a virtual acoustic energy density method is developed in this paper for use in a three-dimensional sound field. This virtual energy density method uses a modified version of the remote microphone technique to estimate the total acoustic energy density at a virtual location. Experimental results of active noise control at a virtual acoustic energy density sensor and a virtual microphone in a three-dimensional sound field are presented for comparison. Minimising the total virtual acoustic energy density with the active noise control system is shown to create a spatially extended zone of quiet at a fixed virtual location compared to virtual pressure control.