I want to put a piezo film in one wall of a one-liter box of water and radiate
a watt or so of ultrasound at a megahertz or so into it, the goal being to set
up planar standing waves (longitudinal of course).  I'm considering starting
with an 8" x 5.5" piezo film for $55 from Measurement Specialties Inc.
What arrangements should I make for a good impedance match to the box?
And which of the 28, 52, or 110 micron thicknesses offered by MSI would
be the most effective for getting the most power into the box (or for any
other reason)?  (Intuitively thicker should handle more power, but then
there's the higher capacitance of thinner...)

Assume that the box is completely rigid, with the piezo film stuck to the
inside of one of its six walls.  (Presumably this would be equivalent to
two infinite rigid plates facing each other with the interior face of one
plate covered with piezo film.  In which case hopefully I'll end up with
very planar standing waves.)

While exact numbers would be nice, (pointers to) suitable formulas would
be more useful.  Alternative approaches, sources of film, ready-made boxes,
etc. also appreciated.

Also, if I want to make the box 10 cm x 10 cm x 10 cm, can I simply cut out
a 10 cm x 10 cm square from the MSI film, or are there things to watch out
for in cutting film?

Vaughan Pratt