Class 323 - buzzing or humming noise?

[trainJam]

I have noticed recently that with class 323s there is sometimes a constant high-pitched whining noise. It isn't necessarily loud, but it does feel like I can hear it even from a small distance away.

Note: I am not referring to the transformer hum.

Does anyone know what it is?

 

[Laurencemcd]

I have noticed recently that with class 323s there is sometimes a constant high-pitched whining noise. It isn't necessarily loud, but it does feel like I can hear it even from a small distance away.

Note: I am not referring to the transformer hum.

Does anyone know what it is?

If it’s a noise only audible from a motor coach you are referring to, then I’ve noticed it as well. It only seems to be audible when one pair of traction motors are isolated on a 6 car set and when the train is taking power. Although you can still hear it faintly when the train is stationary.

I’m not educated in the area, but that would be my guess.