Abstract: The vibration and noise usually occur simultaneously inside the cabin of ship, vehicle and airplane. The vibration causes human body discomfort, while the noise can increase or reduce such uncomfortable feeling. The influence of a typical cabin mechanical noise on the subjective judgment of the discomfort magnitude caused by whole-body vertical vibration is investigated. The low frequency random vibration at three accelerations (RMS is 1.5, 2.0 and 2.5 m·s^-2) combined respectively with the mechanical noise of 70 and 85 dB(A) or only the background noise of 60 dB(A) are applied to the subjects over two minutes for tests. Each of the 12 subjects gave an estimate of the discomfort magnitude caused by vibrations every 30 s. The results show that the discomfort magnitude increases in 70 dB(A) noise and decreases in 85 dB(A) noise, which indicates the double-way masking effects of noise on the discomfort perception caused by vibration:the positive masking (attenuation) effect appears at relatively high noise level and negative masking (enhancement) at relative low noise level; With the increase of the exposure time of human body in the vibration and noise environment, the masking effect of noise on the vibration-induced discomfort decreases.