Does your Hitachi make the motor "sing"?

I own 2 different brands of VFDs. Both brands have adjustable
"carrier frequency" that can be tuned to minimize the noise.

I have 2HP Leeson motors on a couple machines that are inverter
duty rated. I run the carrier freq at 10k (max) on these
machines. There is no noise and they run very smooth.
I run the carrier freq much lower on standard motors. For example
I run around 1.6k on the rockwell surface grinder and a little
bit more on the rockwell mill. The rockwell vertical motor is the
loudest of them all and someday I will replace it with a modern
motor because it also has mechanical resonances and some speeds
which is very annoying.

chuck