degree, $l$, and frequency, $\nu_{n,l}$, as demonstrated in Fig. \[figure\[shift vs freq\]\] . We now look in more detail at these dependencies and discuss what they tell us about the origin of the perturbation. We note here that the frequency shifts plotted in Fig. \[figure\[shift vs freq\]\] were determined for the central frequency of the mode i.e. the $m=0$ frequency. In section \[section\[surface comp\]\] we discuss the latitudinal dependence of the shifts and there we consider modes with different $m$.

![Left-hand panel: Change in frequency between solar minimum and solar maximum, $\delta\nu$, as a function of mode frequency. The results have been obtained by averaging over different ranges in $l$ (see legend), and by smoothing over $135\,\mu Hz$. Right-hand panel: Frequency shifts that have been scaled by the inertia ratio, $Q_{n,l}$. The errorbars on these figures are not visible because they are smaller than the symbol size. Results obtained using GONG frequencies. []{data-label="figure[shift vs freq]"}](freq_dependence_unscaled.jpg "fig:"){width="45.00000%"} ![Left-hand panel: Change in frequency between solar minimum and solar maximum, $\delta\nu$, as a function of mode frequency. The results have been obtained by averaging over different ranges in $l$ (see legend), and by smoothing over $135\,\mu Hz$. Right-hand panel: Frequency shifts that have 