Silencing device and ventilating fan applying same

The invention relates to a silencing device and a ventilating fan applying the same. The silencing device is applied to the ventilating fan with a volute, wherein the volute is provided with a bottomplate and a top plate which are opposite, and the top plate is provided with a through hole. The silencing device comprises a first annular silencing panel and a second annular silencing panel which are arranged on the top plate, and the second annular silencing panel is located at one side, away from the bottom plate, of the first silencing panel; the first silencing panel comprises a first annular wall extending from the edge of the through hole in a direction away from the bottom plate and a second annular wall extending inwards from the top end of the first annular wall and towards the bottom plate, and the second annular wall is provided with a first inner hole; the second silencing panel comprises a third annular wall extending from the top plate in the direction away from the bottomplate and a fourth annula