Generally, a blower generates noise due to air column resonance or the like when blowing air. For example, Japanese Laid-Open Patent Publication No. 1993-228013 describes a technique for reducing the noise of a blower. This publication describes a hair dryer using the principle of the Helmholtz resonator. The hair dryer is cylindrical, and has a built-in motor with a blower fan and a heater to heat the wind. The hair dryer has a casing and a resonator. The casing has a plurality of holes formed at positions where the sound pressure distribution in the axial direction of the standing wave noise due to the air column resonance is high. The resonator is mounted so as to cover the hole of the case. That is, a resonance space is formed between the casing and the resonator, in other words, inside the hair dryer. In this way, this publication describes the idea that sound pressure can be reduced by arranging resonators at a plurality of holes to absorb and attenuate sound of a specific frequency. However, in the structure described in FIG. 1 of Japanese Laid-Open Publication No. 1993-228013, the resonance spaces corresponding to the plurality of holes are not finely divided. Therefore, there is a problem that the noise cannot be reflected in the resonance spaces corresponding to the plurality of holes, and the effect of reducing the noise by the Helmholtz resonator cannot be sufficiently obtained. On the other hand, in the structure described in FIG. 4 of Japanese Laid-Open Publication No. 1993-228013, the casings constituting the resonance space are provided for each hole. Therefore, it is possible to obtain an effect as a Helmholtz resonator. However, since the number of casings for forming the resonance space increases, the number of parts increases. As a result, there are problems that the manufacturing man-hours increase and the manufacturing cost of the blower increases. In addition, since the exterior has a concavo-convex structure, there is also a problem of impairing the aesthetics of the product. In addition, this publication does not disclose a method for ensuring the adhesion of the plurality of outer cylinders.
