Energy loss by internal friction of panel-type sound absorber

摘要

In order to clarify the relationship between the sound absorption characteristics and the properties such as viscoelasticity and size of panel-type sound absorbers, we focused energy loss by internal friction as the main mechanism of sound absorption and evaluated it using fractional derivative viscoelastic model which can express accurately viscoelasticity over wide frequency range. Vibrational state of a panel in an impedance tube was measured directly with laser Doppler vibrometer. We could observe clearly natural vibration by normalizing measured vibration amplitude by an incident sound pressure. Dissipation energy by internal friction was calculated from vibration amplitude and the physical properties of a panel. The ratio of that to incident sound energy agreed well with measured normal sound absorption coefficient.