Particulate dampers for absorption of structural vibrations at audible frequencies. Hasson M. Tavossi, Ph.D., Savannah State University, Department of Engineering Technology, 3219 College St., Savannah, GA 31404.

Absorption of mechanical vibrations by particulate material versus frequency are investigated, with the goal of reduction of transmission of vibrations into building structures. Attenuation of vibration by particulates depend mainly on their mechanical properties, shape, size-distribution, and degree of compression. Structural vibrations can be damped by surrounding them with particulate materials. Experimental results show that, particulate dampers behave as band-pass filters for vibrations that pass through them. The frequencies outside their passband range are strongly absorbed. Some particulate materials have a frequency band-gap, where frequencies in the bandgap range are strongly attenuated by scattering, absorption, or localization of vibrational energy. Samples of uniform size are coupled to mechanical vibrations at different frequency and amplitude. Their vibration absorption versus frequency are determined. Effects of layer thickness, particulate size, orientation, at different frequencies, in the audible range, are measured. The goal is to determine optimal vibration dampers to mitigate the transmission of external mechanical vibrations into the buildings.