If you want silent, an FOC or other sinewave controller with a DD hub will give you as close to that as you can get.
But, depending on your terrain, speed range, usage, riding style, weight of you and trike, winds, etc., it can take a bigger battery and controller to provide the extra power required to do the same job a smaller (but noisier) middrive system can do (if the MD is going thru your shiftable-gear pedal drivetrain).
It might take less power for a smaller geared hubmotor than a DD, depending on the motor, wheelsize, etc. But the geared hubmotor, unless it uses helical gears (not many do) it will be louder in a small wheel for the same speed as it will in a larger wheel, for the same hubmotor winding/design, though it will give more torque.
Most of the systems aren't all that different in overall noise, but depending on your goals some of them are probably unacceptably loud. It's really hard to tell from videos/etc how loud something actually is. The smaller the motor is, the faster it has to spin, and the more it has to be geared down, to give you the same power level that a bigger motor could give directly.
If you want to see how some of this works, you can take your info on terrain, etc to the simulators at ebikes.ca and experiment with the preloaded parts to see what it takes to do what you want to do under your conditions. Takes a bit to learn how it works, but the instructions below it should help with that.