Noisy sound of MX64 motor when its RPM is high like 20 or 30rpm

Hi there,
I am using MX64 motor and struggling with its noisy sound.
Especially when I increase its spinning speed more than 20RPM, the noisy sound is quite annoying.
Are XD series motors quieter than MX64?

All DYNAMIXEL servos will make some amount of noise during operation. XL and XC servos will be slightly quieter, due to their plastic gears producing less noise.

Some DYNAMIXEL users have reported that replacing the included lubricant in the servos with white lithium grease has reduced the amount of noise, but this is not officially supported by ROBOTIS.

Thanks Jonathon for the information.