I also think we're on the same page.
It'd be interesting to measure the SPLs from one meter away from a mpc buzzing (measured at numerous points in a hemisphere with a one-meter radius), then compare that acoustic output to a trumpet played with the same mpc using the same measuring technique. We'd probably need a machine to keep the "effort level" constant from one test to the next.
Even this is full of "errors" since there is sound energy that goes back behind the plain of the mpc or horn. Maybe we'd need to mount each on a large baffle board so that only the forward energy is measured, but being careful not to damp the horn or mpc since that could impede it's energy transfer.
Another interesting comparison would be various horns and mpcs recorded using mics in the ears of the player. (Isnt' that called binary recording mic technique, or something like that? I've got some recording made with such technique and the imaging is incredibly 3D when heard through earphones). Here we'll get more relative information about the energy kicked back to the player and how it varies from horn-to-horn. We might do this with and without the baffle, so we can separate the two sources of acoustic energy.
Dr. Moore, where are you?
Dave