There’s another alternative, Kevin, that I read about but have not tried. It’s to use a guitar pickup and ping the reed. I ping my reeds with a flexible plastic toothpick. Whether harsher pinging would be required and might be risky I don’t know. Your idea might work if the little enclosure didn’t produce bending. I suspect that pinging would produce the most accurate results, but what I suspect often turns out to be false.