I think you are missing the point. The rattle is where combustion starts. It's not a clean start to combustion as with a ignition engine. Hence the sound but that sound relates to the harmonics that are produced. When then are produced they travel through the airframe. It dose not matter what the frequency is if it what of a better term hurts the airframe. That's why the props are different and why the tail fell of. In a metal aframe they also produce cracking. They had an engine that was to be able to be placed into 182 etc but that never really took off ethier.
Cheers