| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for predicting acoustic characteristics such as a vertical incidence sound absorption coefficient, an acoustic impedance, a propagation constant, and a characteristic impedance, about a fiber assembly such as a felt, or a glass wool, and about a foam such as a polyurethane foam or the like. SOLUTION: An effective density valueρ<SB>eff</SB>is calculated, and a bulk modulus value K<SB>f</SB>is calculated, and constants C<SB>v</SB>, C<SB>t</SB>are calculated, and then thermal characteristic length valuesΛ' given on the basis of a fiber diameter and a cell diameter are calculated about the fiber assembly and the foam, respectively. Next, a viscous characteristic lengthΛis calculated, and the characteristic impedance Zc of the porous material such as the polyurethane foam, the felt, or the glass wool, is derived based on the calculated values. COPYRIGHT: (C)2010,JPO&INPIT
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