SGWB spectra (in terms of log₁₀h²Ω_gw) for four different early Universe SGWB models considered in this paper. BOS/LRS correspond to a cosmic string background with N_c = 2 and N_k = 0 (Γ = 57), and log₁₀Gμ = −10.1/−10.6. The GWB from turbulence is plotted in solid line for λ_*ℋ_* = 1, Ω_* = 0.3, and T_* = 140 MeV. The inflationary spectra is shown for log₁₀r = −13.1 and n_T = 2.4 (maximum a posteriori value). Power spectrum of the 2nd-order GWB from the scalar curvature perturbations described by the powerlaw model with $A_{\zeta }^{10\mathrm{yr}}=-2.9$ and n_s = 2.1 is shown with brown puncture-dot line. The nine first Fourier bins posteriors of the common signal are represented by the grey violin areas.