To eliminate an increased space so as to attain a low cost without damaging a function of a cooling tower by a method wherein a deleting audio signal is calculated by a calculation processing part in response to some audio signals obtained through a plurality of microphones, and loud-speaker devices for outputting the calculated deleting audio signal are mounted at a fan casing and a louver.

Fan sound of a fan 3 and dropping water sound flowed from a water dispersion pipe 2 leaked out of a louver 5 and a fan casing 4 are detected by a plurality of microphones 9. A deleting audio signal for use in deleting noise is calculated by a calculation processing part 10. Speakers 11a, 11b for outputting the deleting audio signal calculated at the calculation processing part 10 are fixed to a midway part, an upper part and an outside part of the fan casing 4 and a surface of the louver 5 by a suitable method. With such an arrangement as above, it is possible to attain a low cost without damaging a function of the cooling tower and without increasing a space for it.