Deriving a dangerous area of a road based on a vehicle's noise generated on the road or analyzing a road surface condition based on a driving noise for each vehicle type. An audio signal is collected by a sensor device and send to a noise processing unit. The noise processing unit generates an attenuated audio signal by attenuating a noise other than a noise-of-interest including at least one of a vehicle horn noise and a vehicle sudden brake noise in the received audio signal. An information processing unit detects the noise-of-interest by analyzing the attenuated audio signal through a learned detection model, and establishes a road area within a predetermined radius from the sensor device as the dangerous area of the road based on an accumulated number of times the noise-of-interest is detected.