On 24 Apr 2017 09:44:44 GMT, Huge wrote:



I have also noticed that sound and imagined it to be due to exactly what you have described. A neat way of 'changing gear' electrically instead of mechanically.

Having listened to Tube trains "changing up" as they accelerate out of the
station, and assuming that they can't possibly have mechanical gearboxes,

The Germans and Austrians have tuned some of theirs.
https://www.youtube.com/watch?v=U-nhr5H7mSU

G.Harman