Effects of second sound on acoustic transmission at the solid-liquid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ interface

We have calculated the reflection and transmission coefficients of acoustic waves propagating across a solid-liquid interface of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, using an extension of the treatment of Castaing and Nozières in which we include pressure changes associated with second sound. These calculations account well for the experimental results obtained over the temperature range $0.83 \mathrm{K}\le T\le 1.46 \mathrm{K}$ and provide an alternative explanation to the one we offered previously for the lack of agreement between experiment and the theory of Castaing and Nozières.