Variation in the spectrum shape as function of depth r₀ (model ref). The black line marks the last resolved ridge n = 58 common to all depths. We have volontarily cut the horizontal axis to ℓ = 100 to show the part where ridges are the most visible and used the same color table for the four depths, although the minimum and maximum amplitudes vary greatly. In particular, the change in the background color shows the increase in the background noise when reaching the excitation zone (r₀ = 0.65 R_⊙) and then entering the convective region.