Acoustical analysis and optimization design of the hair dryers

The sound qualities and wind speeds of the four commercial hair dryers (Panasonic, Confu, Flyco, and Philips) were investigated through experimental methods in the present study. The sound qualities included loudness, sharpness, roughness, and fluctuation strength. The experimental results showed that the maximum sound pressure level (SPL) of all hair dryers occurred at about 200 Hz except Flyco hair dryer, which occurred at about 400 Hz. The highest loudness and highest sharpness were found when the hair dryers were set to hot mode and cold mode, respectively. No consistent relationship was found between the effect of room space and SPLs of the hair dryers. The Box–Behnken design method was used to design 13 pieces of oval and rectangular nozzles, and their sound levels and wind speeds were measured. Thereafter, these experimental results were used to derive correlation coefficients between the hair dryer nozzle area, aspect ratio, nozzle length, loudness, and wind speed using the Anova analysis method. Finally, an oval nozzle and a rectangular nozzle with an area of 0.0005 m , an aspect ratio of 1, and nozzle lengths of 0.052 and 0.055 m, respectively, were designed and were tested. These nozzles managed to reduce the sound loudness by 15 and 9.6%, respectively, while maintaining the same level of wind speed.