Resonance widening in spherical GW detectors: model descriptions of the   dissipation processes
  Internal friction effects are responsible for line widening of the resonance frequencies in mechanical oscillators and result in damped oscillations of its eigenmodes with a decay time Q/\omega. We study the solutions to the equations of motion for the case of spherical oscillators, to be used as next generation of acoustic gravitational wave detectors, based on various different assumptions about the material's constituent equations. Quality factor dependence on mode frequency is determined in each case, and a discussion of its applicability to actual gravitational wave detectors is made on the basis of available experimental evidence. 
Eugenio Coccia, Viviana Fafone, Giorgio Frossati, Arlette de Waard,   and J. Alberto Lobo