Literature Survey

A very brief summary of what I've found in the literature with respect to liquid sounds in the air. A proper survey document is to come.

Almost all the sound is generated by bubbles. There are 'slapping' noises related to impacts.
While water/air transmission is very poor, bubbles generated near the surface enjoy better transmission. Bubbles on the surface should have, of course, even better transmission, but I haven't seen any analysis of this.
Bubbles in liquid have a analytical solution for their vibrations which agrees with experiment fairly well. The solution treats the vibrations as a damped oscillator where the mass, stiffness and damping of the oscillator are related to the liquid properties and bubble size. A summary of the solution can be found on this page.
Turbulence in the fluid can generate sound waves, such as in a jet engine, but more commonly it excites existing bubbles to generate sound. An example of this is the gurgling garden hose, apparantly.
One case which has been looked at fairly closely is the impact of a water droplet onto a flat water surface. There have been a few numerical studies of the shape of the impact cavity and lots of attention on the entrainment of a bubble by the impact. You can generate convincing underwater spectra of rain from these studies.