The damping factor, |$\mathcal {D}(k)$|⁠, for a survey where 21-cm modes have k_∥ and μ = |k_∥|/k restricted to the ranges shown. The black lines (upper lines at high k) have no missing modes. Colored lines include the effect of the wedge with μ_min = 0.56 and/or a cut in k_∥; lines for k_∥ ≥ 0.1 hMpc⁻¹, μ ≥ 0, 0.56 are degenerate. The noise of the 21-cm modes, i.e. modes not in the wedge, is taken to be equivalent to |$b^2\,\bar{n}\simeq 3\times 10^{-3}\,h^3{\rm Mpc}^{-3}$| (see text). Two directions are shown: solid lines are along the line of sight (k_∥ = k, k_⊥ = 0) and dashed lines are transverse (k_⊥ = k, k_∥ = 0). Solid lines are ordered at large k according to k_∥ ≥ 0, 0.02, 0.1, top to bottom, with μ ≥ 0 higher than μ ≥ 0.56 for each k_∥ cut. Top: |$\mathcal {D}(k)$| for modes which are present (obeying k_∥ and μ_min cut), P_N = ∞ or |$b^2 \bar{n}\rightarrow 0$| for missing modes. Bottom: the same cuts in k_∥, μ, as above, but replacing the missing modes with an ELG survey with number density 3 × 10⁻⁴ h³ Mpc⁻³. For |${\mathcal {D}}(k=k_\perp )$|⁠, the line order at large k top to bottom is the same as in the legend. Note in the top figure that with our approximations a small range of k_∥ is improved when other modes are completely left out of reconstruction, an example of increasing noise increasing |$\mathcal {D}(k)$| for some k and suggesting that a different smoothing may help with better recovering those components.