Active Noise Control Using Acoustic Wave Reflection of a Parametric Loudspeaker

Abstract

This paper deals with active noise control (ANC) using an acoustic wave reflection of a parametric array loudspeaker (PAL). Making use of the strong directivity of a sound radiation a PAL has, it is possible to avoid spillover phenomenon leading to the augmentation of sound pressure in other region of the targeted control point. The strong directivity, however, may be double-edged for ANC. If an obstacle exists between a PAL and a target control point, it may no longer achieve ANC as a sound diffraction cannot be expected. To overcome this problem, this paper presents a control strategy based upon the use of a sound reflection, and hence the sound beam of a PAL may detour the obstacle, arriving at the control point. First, fundamental properties of a sound beam reflection are investigated, thereby assuring the possibility of a sound reflection for ANC. Furthermore, mathematical description of a sound beam is performed using a mirror image method, control effect of ANC being clarified. Finally, an experiment is conducted, demonstrating the validity of the proposed method.