Patent ID: 8123468

Claim:
A centrifugal fan comprising, in an outer casing having an opening, a motor that couples an impeller so as to rotate the impeller on a rotational axis, a casing that surrounds a periphery of the impeller and has a suction port, and a bell-mouthed orifice that has an opening communicating with the opening of the outer casing, the centrifugal fan resonating and suppressing noises released from the suction port by a resonant space formed by the orifice, wherein part of a path where sound waves of noises incident from an inlet portion between an end of the orifice and the casing into the resonant space are reflected is made longer, a wall body is provided in the resonant space and the part of the path where sound waves of noises incident into the resonant space are reflected is made longer, and the wall body provided in the resonant space has a cylindrical pipe shape that is concentric with the suction port and has one end contacting the casing.