"Nick" wrote in message ...
I think I used to hear the same noise further along the Picadilly Line at
Northfields.
My guess is that long stretches of track in the open air can develop a 3D
vibration and the noise is a natural harmonic of the length of rail.
The steel is, I guess, less beefy than the heavy rail tracks that don't make
the same sort of noise.
It's a funny boinging, jittering noise isn't it?


That's right. The tracks at Turnham Green are relatively free of
points on the eastern side, but on the western side there are points
where the Richmond spur of the District Line splits off. The
Piccadilly Line is free of points, so you can hear the twanging from
either direction. It's certainly the best reason I've heard so far.

And it does sound like a jittery, bonging sound to me; exactly like a
huge spring is being twanged back and forth in a small space. At least
now I know that I'm not going crazy or anything..... ;-)

Brad Chapman