Bill Daniels wrote:
...
1. A constant speed prop reduces the blade AOA and lets the engine rev to
its redline RPM. (Noisy)
2. Big, slow turning props make much more thrust at low speeds than small,
high RPM props. (Quieter but require PRSU gearbox)

Both constant speed and low RPM through an appropriate gearbox are
provided in the Super Dimona we use as tow plane. The noise is noticeably
lower than with a conventional prop, although the prop is of slightly
lower diameter than most of them. The noise reduction was sufficiently
significative that we got some help from the general fundings for
noise reduction. If we didn't had a lot of problems with the engine,
this would seem a very good solution.