Sound field equalization by active acoustic impedance control

This study examined sound field equalization by using active control. The specific acoustic impedance, the ratio of sound pressure and particle velocities is adopted as a target of control. Providing the impedance in the aimed direction is controlled to be the characteristic impedance of the medium, the propagating plane wave in any particular direction would be expected. In addition, the directional characteristic of the sound propagation can also be controlled by adjusting the weight of ratios of pressure and velocity in three orthogonal directions. The results of numerical simulations using impulse response measured in a small enclosure indicate the potential efficiency of the proposed method and the propagating plane wave could be observed. Furthermore, the results of subjective experiments indicate that the proposed method may alter the perceived direction of incoming sound by controlling the sound field nearby the human listening position.