VIBRATION REDUCTION DEVICE FOR VEHICLES

PURPOSE:To optimize the vibration for reduction in units of 1 period, i.e., to enhance the effect of the reduction of vibration when the period is changed. CONSTITUTION:The periodic first vibration generated due to the rotation of an engine 8 is reduced by the interference action of the second vibration (vibration for reduction) outputted from a loudspeaker 11 installed in a cabin 2. The second vibration is set in units of 1 period of the first vibration, and the vibration energy of the second vibration is corrected in accordance with a signal from a microphone 12 for detecting a vibration in the cabin 2 and the transfer characteristics between the microphone 12 and the loundspeaker 11. If the phase of the second vibration deviates from an adequate value due to the fluctuation of the rotation period of the engine 8, the phase of the second vibration is adjusted so as to compensate the deviation of the phase. The adjustment of the phase is executed in accordance with the dominant order-component by which the noise level is made higher, e.g. in accordance with the 6th component in the low rotation region and the 3rd component in the high rotation region when the engine 8 is of V type 6-cylinder.