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1·Another haunted and related natural phenomenon is known as frequency infrasonic sound waves.

另一种与闹鬼相关的自然现象是称作次声的低频声波。

2·The primary results show that the ultra low-frequency pulses may produce in the process of nucleation of micro-cracks and faults, and transmit to the air as infrasonic sound.

初步结果表明，微破裂的集结和断层的破裂起始会出现超低频脉冲，并透射到空气中形成次声波。