SOUND ABSORBING MECHANISM

摘要

PROBLEM TO BE SOLVED: To provide a constitution by which the optimum sound absorption characteristics can be obtained for a sound absorbing mechanism constituted by combining a 1st sound absorbing structure which has a plate type sound absorbing material provided in a slit opening part and is based upon Helmholtz resonance and a 2nd sound absorbing structure which has a mere air layer behind a plate type sound absorbing material. SOLUTION: The peak frequency of sound absorption characteristics to a 0 deg.-incident sound wave that the 2nd sound absorbing structure has in a design frequency band is >=2.5 times as high as the peak frequency of sound absorption characteristics to the 0 deg.-incident sound wave that the 1st sound absorbing structure has; when the sound absorption characteristics that the 1st and 2nd sound absorbing structures show are put one over the other, mount parts of the sound absorption characteristics that the 0 deg.-incident sound wave shows match valley parts of nearly M-shaped sound absorption characteristics that the 0 deg.-incident sound wave shows within a range of <=±l5% and the sound absorptivity of the valley parts of the nearly M-shaped sound absorption characteristics that the 0 deg.-incident sound wave shows is >=0.75.