  The propagation of wave disturbances over a vertically oscillating liquid may
form standing waves, known as Faraday waves. Here we present an alternative
description of the generation and evolution of Faraday waves by nonlinear
resonant triad interactions, accounting for gravity surface effects and the
slight compressibility of the liquid. To this end, we analyse a triad
comprising an infinitely long-crested compression mode and two oppositely
propagating subharmonic surface waves.
