Not sure if this is the right place. Moderator, please move if inappropriate.
I'm in the process of plowing through a paper by Wolfgang Klippel. I think it could be useful for the amateour DIY'r to get a deeper understanding on how our beloved transducers work.
http://www.klippel.de/pubs/Klippel%2...ymptoms_06.pdf
The paper is nicely illustrated by both formulas and graphs.
-Tim