Theory of adiabatic fountain resonance
  The theory of "Adiabatic Fountain Resonance" with superfluid $^4$He is clarified. In this geometry a film region between two silicon wafers bonded at their outer edge opens up to a central region with a free surface. We find that the resonance in this system is not a Helmholtz resonance as claimed by Gasparini and co-workers, but in fact is a fourth sound resonance. We postulate that it occurs at relatively low frequency because the thin silicon wafers flex appreciably from the pressure oscillations of the sound wave. 
Gary A. Williams
cond-mat.other