The principal objectives of the work reported in this paper were two-fold. Firstly, to assess, by means of the numerical simulation of transverse wave propagation within a linear viscoelastic medium, the degree to which wavegroup propagation involving a finite frequency interval (2Deltaomega) corresponds to an 'ideal' beat (i.e. one for which 2Deltaomega --> 0). Secondly, to compare the results of shear wave propagation measurements with predictions based on a rheometrical theory, which describes the gelation of materials in terms of their wave dispersion characteristics. The results of the numerical simulations indicate that for a sufficiently small value of the frequency interval Deltaomega/omega, the nodal and anti-nodal regions of the amplitude modulation envelope of wavegroups propagating within a critical-gel may be defined with sufficient accuracy to permit calculation of the corresponding value of the group velocity U. The results of high frequency shear wave dispersion measurements made on a system known to display critical-gel behaviour provide encouraging agreement with theory and the results of the simulations. (C) 2004 Elsevier B.V. All rights reserved.