粉体層の音響特性に及ぼす粒径の影響

吸音特性と音速

抄録

The sound absorption coefficients and sound velocity of various powder beds were measured in the frequency range of 200Hz to 2kHz. The powder beds were comprised of classified powders having mean particle diameters from 53 to 300μm. For the powder beds consisting of smaller particles, the sound absorption coefficients showed distinct peaks due to the excitation of normal vibration modes of the powder bed. In the frequency range in which sound absorption peaks appear, the sound velocity has almost on frequency dependency, and sound energy is dissipated mainly by the interaction of vibrated particles. As particles with larger diameters were used, these peaks decreased in amplitude, but the level of sound absorption increased in the high frequency range. In this frequency range, sound velocity increases according to frequency, and sound energy is dissipated mostly by the viscosity of the air in the pores.