12 hours of Enterprise-D engine idle noise:
https://www.youtube.com/watch?v=aRk-DQUUlz8
10 hours of American Airlines hold music (as one commenter there said - likely recorded from a real call):
https://www.youtube.com/watch?v=aRk-DQUUlz8
10 hours of American Airlines hold music (as one commenter there said - likely recorded from a real call):