Which motor don't have high pitch noise?

Hello

I'm now very fan of sine wave controller because it makes motor silent .

I have now the phaserunner as well as the Kelly 7230s controller.

I noticed on my leaf motor, it runs completely silent.

But on another direct drive motor, there is an annoying high pitch noise on the phaserunner.

Is it normal? What motor combination are completely silent?

I'm looking for peace