"Nigel Pendse" writes:

Presumably the sound seems louder because the Piccadilly Line trains are
normally non-stopping and running through the station relatively fast. There
aren't many other stations with Tube trains passing through at speed.

Jubilee Line between Wembley and Finchley Rd (IIRC the noise from Met
Line trains is the same).

I also wondered if the steel girder bridge immediately to the west of the
station plays any part in the noise?

It probably gives the Turnham Green sound a unique aspect.