PURPOSE: To damper remarkably vibration transmitted from a rotator to a building and prevent beforehand the occurrence of the secondary noise by filling the hollow portion of a rotator fitting mount with sand-like grains.

CONSTITUTION: At the starting time of the speed change motor of a ventilator 1 or at the time of wind quantity increase/decrease due to speed change, vibration occurring around the rotary shaft of the ventilator 1 is transmitted to a rotator fitting mount 2, and then, the resonance operation of transmitted vibration according to the mode of vibration proper to the base 13 and the box body 14 or the like of this fitting mount 2 is remarkably damped on account of the mass of sand-like grains S filled into the hollow portion 16 of this fitting mount 2 and friction among grains. Accordingly, vibration generated by the ventilator 1 becomes hard to be transmitted to the ceiling slab 6c of a building 6. As a result, vibration in other rooms and the occurrence of secondary noise are prevented.