論文ID: e25.28
A method for adjusting room acoustics through active control using conventional loudspeakers as secondary sources is proposed to suppress inhomogeneity caused by standing waves and room modes. Unlike conventional active control, the control target is the specific acoustic impedance, which is the ratio of sound pressure to particle velocity. The aim is to approach a sound field with only direct waves and no reflections. First, to perform the control, the condition for the maximum absorption coefficient of the virtual boundary surface was determined from the perspective of impedance matching, and an error function was set. Next, a particle velocity measurement method was introduced to obtain the values of specific acoustic impedance, and the weighting of sound pressure and particle velocity was modified. Furthermore, using these tools, experiments were conducted using both a real sound field and simulations to verify the effect of impedance control. Finally, impedance control was reinterpreted from the perspective of microphone directivity, clarifying the control mechanism. The results confirm the method’s effectiveness in low-frequency sound field adjustment, where passive absorbers are insufficient.
