Abstract: Two sub-wavelength sound absorptive structures were designed for the range hood. One basic sound absorptive unit is based upon the quarter wave length resonator theory, and the other basic sound absorptive unit is based upon the Helmholtz resonator theory. Having maximum noise reduction level and better sound quality, the sound absorption coefficient of these two sound absorptive structures were designed optimally according to the selective noise spectrum of a range hood. The design lowest wave length is more than twenty times than the thickness of the sound absorptive structure.

Key words: Acoustic metamaterial, Optimized design, Sound absorptive structure, Selective frequency band, Sub-wavelength structure