I have just purchased a brand new Bachmann SY9 2-8-2 DCC Mikado.  I am trying to run it on Bachmann DCC controller.  When I first address the engine it is perfectly quiet but when I start increasing the speed control it starts making a very noticeable humming or vibrating sound.  Eventually the engine starts moving but the sound continues.

What is wrong and what do I do about it?

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