LOW-FREQUENCY ACOUSTIC BEHAVIOR OF HIGHLY POROUS, LAYERED, FLEXIBLE, FINE FIBER MATERIALS

This paper is concerned with predicting the acoustic behavior of highly porous, layered, flexible, fine fiber materials at low frequencies. A theoretical model of fiber behavior is developed that consists of two independent modes of vibration that exhibit resonance at zero frequency and a finite frequency. This model also incorporates a fiber parameter g that governs the fraction of fibers that can resonate which is now hypothesized to be frequency dependent and was found to range between a comparatively low value g0 near zero frequency and a high value g∞ at higher frequencies. These asymptotic values and the location of the transition region were found empirically. There is good agreement between this model and experiments designed to measure the effective resistivity e and the effective density pe of the fluid in the pores of the fibers over a wide range of frequencies. © 1995, Acoustical Society of America. All rights reserved.