To minimize abrasive noise close to the ears of a worker passing through a pillar such as a head guard.

An inside of the pillar erected in a car body is utilized as a open air intake passage, and an inlet is opened downward apart from a cavity top end inside of the pillar. A resonance restraining component is arranged in a dead-end space D inside of the pillar in the upper part of the inlet to suppress the resonance of the noise generated in the space D. The sound intensified by the resonance of the noise and the reflective wave generated at the time of engine operation is cancelled by the resonance restraining component in the space D, and the emission of the noise generated by the resonance from the inlet is suppressed.