force may be applied to the second additional mass body 32 by means of actuator 37 support frame 33 rests on structure s the hanger means 35 of the first additional mass body 31 allows vibration of the additional mass body 31 in all horizontal directions by for example providing universal joints 35a and 35b the second additional mass body 32 may be vibrated in only one direction but the direction of vibration can be restricted by the actuating direction of the actuators 37 in the embodiment of fig6 support means 33 rests on structure s the hanger means 35 of the first additional mass body 31 is similar to hanger means 35 of fig5 the second additional mass body 32a is arranged so as to slide on the first additional mass body 31 with anti friction means such as rollers 38 the direction of movement of mass body 32a can be controlled by the rotational direction of the rollers 38 the axial alignment of coil spring 39 connected between the second additional mass body 32a and first additional mass body 31 and the axial alignment of the actuator 37 in lieu of rollers 38 it is contemplated that mass body 32a be vibrated on rail means such as rail means 18a or 18b of fig3 and 4 in the embodiment of fig7 the hanger support of the first additional mass body 31b is similar to that shown in fig5 a concave arcuately curved track 40 on the upper surface of the first additional mass body 31b is.