  Andreev billiards are finite, arbitrarily-shaped, normal-state regions,
surrounded by superconductor. At energies below the superconducting energy gap,
single-quasiparticle excitations are confined to the normal region and its
vicinity, the mechanism for confinement being Andreev reflection. Short-wave
quantal properties of these excitations, such as the connection between the
density of states and the geometrical shape of the billiard, are addressed via
a multiple scattering approach. It is shown that one can, inter alia, hear the
stationary chords of Andreev billiards.
