Greg - Appreciate your knowledge and advice......very helpful. I found in the ESU LokSound 5 Instruction Manual the following guidance: "In the LokSound decoders load control works with 40kHz normally. Sometimes it can be useful to reduce this frequency by half for motors with little power due to high inductivity, or if suppressors (e.g., capacitors, chokes, etc) disturb load control but cannot be removed."Yes, auto cal... notice you say the loKProgrammer settings are fine, but the motor still buzzes... So if it was me, I would try the auto cal, in case it does better, I really don't see how you can assume the stock settings are the best... and how you can be sure they have nothing to do with the buzzing.
Again, turning BEMF off stops the buzzing, right? Auto cal affects BEMF settings, right? Your statement says they have nothing to do with each other.
I did make a recommendation on PWM frequency, something ultrasonic... which is normally defined as over 20 or 21 KHz....
I don't know what the decoder can do but I can give you a recommendation that is normally the most quiet for any motor... maybe not the best performance for all motors.
on the supressor circuitry, I have never found it inside the motor.