Hi everyone, I am looking to improve the transmission of sound from a small 1/2" electro-mechanical transducer through a plastic medium (about 1/4" thick). I understand plastic is not a great medium for this but I do not have the ability to change this. The defacto setup doesn't work too terribly, but at certain times the sound, especially higher frequencies, is muffled. I've been looking into the use of coupling agents (such as gelatin, oils, etc) to help with this. What are the exact properties of the coupling agent that I should be designing around? Should it match the acoustic impedance of the plastic medium? Of the transducer? The average? What should the thickness of the agent be relative to the medium? Any help appreciated, thanks!