PURPOSE: To prevent the generation of the striking sound at the opening of a shutter and ensure the opening and closing of the shutter due to the elasticity of the tongue of a cushioning medium by a structure wherein the elastic tongue is provided on the cushioning medium arranged between the shutter and an exhaust frame of the exhaust port of a ventilating fan.

CONSTITUTION: An exhaust dust 11 is provided through an exhaust frame 7 to a ventilating fan main body 1. A tongue 21a held by the supporting plate 22 of a cushioning medium is provided at the exhaust frame 7. When a fan 4 is put into rotation, a shutter 18a is open by air pressure so wide as to push the tongue to the position inducated with the dotted lines 21c. At this time, no striking sound generates between the tongue 21a and 19a of the shutter. When the ventilating fan is stopped, the reaction generated by the deformation, which is developed at the opening of the shutter, of the tongue is applied to the shutter in the direction so as to close the shutter, resulting in enabling to surely close the shutter. In addition, the ratio of air flow rates can be improved by the degree of the open angle.