In a disk array apparatus, by taking note of a first sound of a specific frequency which is a noise element of original sounds generated from a fan, a second sound whose phase is inverted to that of the first sound is generated by a structure of a cooling air flow path passing through the fan, and the second sound is synthesized with the first sound on the cooling air flow path, thereby reducing the noise. For example, an exhaust duct is located on a fan unit in an upper part of the apparatus, two flow paths extending to an exhaust port are formed in an internal structure of the exhaust duct, and the two flow paths are designed so that the difference in the flow path length therebetween becomes equivalent to half wavelength of the specific frequency.