Two averaged (effective) models corresponding to transverse and longitudinal oscillations in a periodic combined stratified medium are constructed. The medium considered consists of alternating layers of an isotropic viscoelastic material and a viscous compressible fluid. The dependence of the qualitative characteristics of the spectra of the averaged models on the linear dimensions of the stratified medium specimen is investigated.Summing the results obtained, we can assert that for l ≤ π/ √ ρ 0 M 1 the spectrum of problem (2.1), (2.2) is the union of three series {λ 1k }, {λ 2k }, and {λ 3k } (k ∈ 1, 2,... ) of real numbers. Now consider the case of l > π/ √ ρ 0 M 1 . Here, the spectrum of problem (2.1), (2.2) is the union of a series {λ 1k } (k ∈ 1, 2,... ) of real numbers and two series {η 2k } and {η 3k } (k ∈ 1, 2,... ) each of which may contain not more than d 0 = [l √ ρ 0 M 1 /π] complex numbers ([ ⋅ ] is the integer part of the corresponding number). Namely, if for the given k the roots of Eq. (2.8) are real, then η 2k = λ 2k and η 3k = λ 3k ; on the FLUID DYNAMICS Vol.