Abstract ▼ AI-Helper

Acoustic properties of porous soundproofing materials can be predicted by using many macroscopic physical parameters. In this study, Biot's and Allard's theories are utilized for relating various parameters to each other, and after estimating all the parameters, either by measurement or prediction, ...

Acoustic properties of porous soundproofing materials can be predicted by using many macroscopic physical parameters. In this study, Biot's and Allard's theories are utilized for relating various parameters to each other, and after estimating all the parameters, either by measurement or prediction, the absorption coefficient of a sample is estimated. Because the measured porosity is very near to unity and the flow resistivity is very small in the polyurethane foam sample, the rigid frame model is suitable for describing the acoustic characteristics. The bulk and shear moduli of the frame are measured at low frequencies, whereas the tortuosity and characteristic lengths are estimated from the measured impedance of the foam. Although the tortuosity and characteristic lengths are tried to estimate by using the finite element model of the microstructure of the foam, the calculated values are different from measured data due to the complexity of the structure. Finally, the statistical absorption coefficient of layered polyurethane foam with a thin impervious screen are predicted from the obtained parameters. The result is compared with that measured in the reverberation room chamber, and with that estimated from the standing wave ratio in the impedance tube test. It is observed that the present result agrees reasonably well with that from other methods except at major peak band.

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