Inversion of bending wave properties of viscoelastic panels from laser Doppler vibrometer measurements

Abstract

Thin panels of viscoelastic materials have been shown to have tremendous sound transmission loss enhancement characteristics when implemented in sandwiched gypsum wall panels. However, it is challenging to obtain reliable dynamic mechanical properties of these materials across relevant building acoustics frequencies. To better understand the dynamic mechanical properties of these materials, a methodology employing bending wave characterization is discussed. Relying on inversion processes from the measured panel velocities, this methodology yields loss factors, complex elastic moduli and phase speeds. The dispersive nature of these bending wave phenomena in viscoelastic panels opens a unique set of challenges for reliable dynamic mechanical property characterization. This paper discusses these challenges as wells as an approach to mitigate these effects and improve measurement reliability.