Numerical simulations using viscoelastic wave equations allow investigation of interactions between the effects of scattering by variations in P velocity, S velocity, density, and intrinsic Q for both P and S waves. When variations are spatially correlated between the parameters in a scattering medium, the amount of scattered energy increases. Thus, neglect of the contribution of any parameter to scattering will result in biased estimates of the contributions by the other parameters; this is especially true if interactions between intrinsic and apparent Q are neglected. The presence of finite intrinsic Q values has two effects; the overall amplitudes of both the incident and scattered waves are attenuated, and new scattering is introduced by the spatial variation of Q. The energy in the coda is reduced substantially and shifted to lower frequencies by attenuation in a viscoelastic medium. For a given scatterer size, the frequency at which the dominant scattering occurs is lower for S waves than for P waves.