Part of the experience of being in New York City — whether you live there or are just visiting — is the sound.
Depending on exactly where you are in the city, you expect to hear something in particular. If it’s a bit off, you’re likely to notice.
The MTA is looking for ways to cut the amount of time subway trains sit at platforms, and one proposal will change the audio experience. They’re already testing one possible change.
The link goes to a June 19 Gothamist.com article with plenty of audio and video samples to satisfy any outsider’s craving for New York subway mood stuff. You may find it disappointing because the rats are missing, but you’d be surprised at how many rats in an urban subway system never show their faces.