So what's the best sounding train you've been on? I think the DC metro handily wins that for me. It's got an electric hum that mutes nicely when the doors close, and they do so with a big whoosh, and the acceleration changes the sound very smoothly, and there at least used to be a nice "driving over metal plates" sort of soft cracking on some of the track.
It also has a nice trackside experience in the stations.
Worst was probably metrolink in LA, because it didn't sound like much at all. 
@pamela i’m very partial towards the gentle clanking rattle of SEPTA regional rail (South Eastern Pennsylvania) personally, though thats admittedly in part because I grew up with it
Worst is without a doubt London’s metro system, where evidently not a single thought was spared towards the passengers’/crews’ auditory comfort. At least half the lines squeal loudly enough to make one worry about hearing damage at every curve (and the london metro is nothing *but* curves)
@pamela (source backing up my london complaints, because its truly difficult to describe without sounding like one is being hyperbolic: https://www.wired.co.uk/article/london-tube-underground-noise )
@pamela its TERRIBLE and the city is just like “thats what trains are like sorry :/“ even though nowhere else is like that!!!!
@Satsuma oh that's not okay XD