I have started using the sennheiser pxc250 on the BART train. You
can still hear the train noise — it’s reduced, but not as much as
earplugs you might buy for a couple of dollars. Also, some of the
BART noise is the metal wheels against metal tracks which is high
pitched and is not cancelled by the circuitry that is designed for
lower pitched noise. I haven’t tried adding music yet which is what
the headphones were designed for. Probably an in-the-ear design (such
as etymotics) would provide better noise isolation than open-air with
I tried it in a machine room with lots of equipment fans. You can hear
noise, outside of headphones, but it does indeed reduce the intensity.
It would be better if the phones fit the ears tighter.