Music of the spheres: sound emitted by the bubbles in liquid helium
  A large linewidth of electronic transition of an electron trapped in a bubble ("bubblonium") possesses natural, or radiative, and inhomogeneous components. The latter mechanism of the line broadening requires dissipation. Dissipation of optical-frequency quantum into a liquid helium leads to an emission of an acoustic wave. The possibilities of detection of this acoustic signal are discussed in this paper. Finally, the low temperature analogues with several hard-to-observe astrophysical phenomena are discussed. 
Peter B. Lerner
cond-mat.other