| 摘要 |
PROBLEM TO BE SOLVED: To simply and inexpensively provide means to reduce noise in an elevator car effectively and stably by suppressing acoustic standing waves which occur in the elevator car; and to provide a structure which achieves the means.SOLUTION: A car is composed of six surfaces (a floor surface, a ceiling surface, a front surface, a back surface, and both side surfaces), and supposing that the shape of a ceiling as looked up from the inside of the car is substantially rectangular, reference microphones are each installed near the center of each of four sides constituting the rectangle. A secondary sound wave generator installed at the center of the ceiling surface generates signals for generating secondary sound waves based on sound pressure signals collected by the plurality of the reference microphones, and the signals for generating secondary sound waves are converted to sound to radiate by the secondary sound wave generator disposed on the ceiling.SELECTED DRAWING: Figure 3 |
