Mike Confalone has compiled a 50-minute audio file of looped switching sounds -- air pops, wheel squeal, coupling, etc. -- into a 50 minute file. He velcros a bluetooth speaker remote to his throttle and moves the speaker around the room as needed. It's an interesting concept, to give a better sound experience for switching ops. Personally, I enjoy the RP braking and coupling sounds, I wonder how this could be incorporated into RP. Mike's demo vid is only available on the Allagash Facebook account.
Here's the sound file (no video):
t=2436s
During op sessions, my friend Dave Abeles plays a continuous lower octave rumble through free-standing amps just loud enough to create a realistic but not annoying diesel prime mover ambience in his basement.
Tony Koester also has chirping bird sounds for when you're running out in the middle of Nowhere, Indiana on his NKP layout.