Acoustic potential V(r) used in Eq. (8), calculated using Eq. (7) and the equilibrium state of the Sun given by the solar patched model described in the text. The radius is normalised by the photospheric radius R_⊙, and only the outermost region is shown. We note that the acoustic potential is normalised by here (where R_⊙ is the radius of the solar photosphere) so that it is dimensionless.