Noise reduction device for cooling fan and engineering machinery

The utility model discloses a noise reduction device for a cooling fan and engineering machinery. The noise reduction device for the cooling fan comprises an outer frame, a noise reduction air channel and a noise reduction material. The outer frame is provided with a containing cavity, an air inlet I and two air outlets I, wherein the air inlet I and the two air outlets I are communicated with the containing cavity. The noise reduction air duct is assembled in the containing cavity and is composed of a main air duct and a secondary air duct, one end of the main air duct and one end of the secondary air duct are connected to form an air inlet II connected with the air inlet I, and the other end of the main air duct and the other end of the secondary air duct form two air outlets II connected with the corresponding air outlets I respectively; a gap between the noise reduction air channel and the outer frame is filled with the noise reduction material. The noise reduction device adopts a two-stage expansion cham