Upper panels: visibility of the ℓ = 1 modes as a function of T_eff in the left panel and of ν_max in the right panel. The colours and symbols are the same as in Fig. 5. The error bars are computed in the same way as in Fig. 5. Similarly, error bars on the visibilities are given for both low ν_max (ν_max ≤ 4.5 μHz) and high ν_max (ν_max ≥ 4.5 μHz). The dashed lines are the fits presented in Table 4, in light blue for RGB stars and in light red for He-burning stars. The thin solid light blue and light red lines are the fits obtained for less evolved stars (Mosser et al. 2012) for RGB stars and for He-burning stars, respectively. The thin solid black line is the theoretical prediction (Ballot et al. 2011b). Middle panels: same labels as in the upper panels, but for the visibility of ℓ = 2. Lower left panel: same labels as in the upper left panel, but for the visibility of ℓ = 3 modes. The median values are computed in 50 K wide T_eff bins and in 1.5 μHz wide ν_max bins.