| 摘要 |
PROBLEM TO BE SOLVED: To effectively reduce low-frequency sound pressure in any direction from two machines as generation sources of the low-frequency sound when attenuating the low frequency sound generated by the two machines with vibration sources by canceling it out each other by a phase difference.SOLUTION: For every regular or nonregular any time interval, an operation X is performed. The operation X includes: "in a direction of reducing the low frequency sound at a position separated from machines (1a) and (1b), controlling driving conditions of the machines (1a) and (1b) while measuring low-frequency sound pressure generated by the machines (1a) and (1b); changing a phase difference of the low-frequency sound generated by the machines (1a) and (1b); and obtaining an optimal phase difference &Dgr;P". The optimal phase difference &Dgr;P in which the measured low-frequency sound pressure is minimized in the direction of reducing the low frequency sound is thus obtained by performing the operation X. After performing each operation X, the machines (1a) and (1b) are driven under such driving conditions as forming the optimal phase difference &Dgr;P. |
