Abstract
Passive noise control such as sound absorption and sound insulation is commonly used as noise reduction measures. It is effective against high-frequency noise, but not effective against low-frequency noise. As appropriate measures for the low-frequency noise, there is active noise control (ANC) system. The system generates a sound whose amplitude is same as noise and phase is opposite to noise. The sound causes the acoustic wave interference and erases the noise. It is used well in one dimension space like the duct, but there are few examples of practical use in three dimension space. Then, we developed the ANC system that can be applied to three dimension space.
