629 一次音源が移動する音場での仮想マイク法による能動音響制御

Abstract

Local active noise control systems create a zone of quiet around a physical error sensor location. The zone of quiet is generally small, and as such, the physical error sensor is placed at the desired location of sound attenuation, which is usually inconvenient. Virtual sensing algorithms have been developed to aim for creating the zone of quiet at virtual sensor location that is remote from the physical error sensor. However the sound attenuation of the traditional virtual sensing algorithms worsen by change of primary source location that alter the transfer characteristics between a virtual sensor and a physical sensor. This paper presents a method to approximate the transfer characteristics between a virtual sensor and a physical sensor by superposition of several transfer functions calculated from acoustic paths using positional information of primary source. The transfer function is expressed a dead-time component and a coefficient vector for amplitude correction calculated by Maekawa's curve. The effect of control using the approximated transfer function in numerical simulation indicates that around 5dB of attenuation can be achieved.