Examples of a typical QS f-mode spectra. Top: example of QS ring diagram at the angular frequency ν = 3.57 mHz for one quadrant of the full ring (logarithmic color scale), computed from the data cube presented in Fig. 4 (left panel). Bottom: collapsed spectrum obtained by integrating over the ring diagram. The red vertical line marks the position of the maximum of the f-mode and the black vertical lines the range of integration. The wavenumber k is expressed in units of the circumference of the Sun (C_Sun).