Elastic membrane
= Elastic membrane
{title2=$\eta$}
An elastic membrane is a thin deformable sheet whose transverse restoring force is supplied by in-plane tension. For uniform tension $T$ and mass per area $m$, a two-dimensional small-displacement model has $m\eta_{tt}=T\eta_{xx}-[p]$, where the pressure jump is defined from the lower fluid to the upper fluid. Fluid loading modifies its traveling modes through the <acoustic wave on a tensioned massive membrane>.