Development of a quiet, yet quick drying hair dryer

Abstract

The hair dryer noise is dominated by the flow noise which is involved in various parts in the interior. In general, the flow speed and the amount of turbulence strength are the important points in the low-noise design, but the designer will meet a trade-off condition of the flow rate that is related to the drying speed. In this work, the state-of-the-art techniques for the quiet design strategies of major air-borne sources such as the fan, shroud, exhaust nozzle, and inlet grille are studied first and the characteristics of their major parameters are identified. Then, each noise source part is redesigned to produce the lowest noise, while obstructing the flow minimally. Instead of using a single fan, multiple smaller fans are used to reduce the broadband noise. Two types of quarter-wavelength tubes are installed within the shroud to reduce the blade passing frequency (BPF) tones. Additionally, a fan with unevenly-spaced blades is tested to eliminate the BPF. The jet noise at the exhaust nozzle is reduced by using the dual-tube: slow flow speed in the outer tube reduces the shear. The inner tube end is shaped with lobes. Spiral grille pattern is used for the lowest inlet turbulence and noise. Sound reduction through the shell is calculated. The acoustical and aerodynamic performance of the final prototype, which is an assembly of all lownoise design parts, is evaluated. Compared with the 4 competitive products in the market, the developed hair dryer reveals that the flow rate is higher by 20%, the overall sound level smaller by 6 dB, the loudness smaller by 30%, the sharpness by 15%, and the roughness by 9%.