Fraction of mode energy reflected at the bottom of the acoustic cavity for a 1.6$\mso$ star ascending the red giant branch (decreasing $\nu_{max}$). The lines show values for modes with $\ell=1$ and $\ell=2$ and their ratio.  
The degree of reflection is determined by the tunneling integral through the evanescent region as $1-T^2$, where the tunneling integral $T$ is defined in Eq.~\ref{eqn:integral}. The range of values for the fraction of $\ell=1$ mode energy reflected during core He-burning is also shown (hatched region).\label{visibility}