  Internal friction effects are responsible for line widening of the resonance
frequencies in spherical gravitational wave detectors, and result in
exponentially damped oscillations of its eigenmodes with a decay time which is
proportional to the quality factor of the mode and to its inverse frequency. We
study the solutions to the equations of motion for a viscoelastic spherical GW
detector 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
detectors is made.
