This is the Discovery One ambient ship noise from 2001: A Space Odyssey for 12 hours. It is great for relaxing. meditating, falling asleep, and especially imagining that you are in deep space.
" United States Spacecraft Discovery One is a fictional spaceship that appears in The Space Odyssey series, including the motion pictures 2001: A Space Odyssey and 2010: Odyssey Two. Discovery One is a nuclear-powered interplanetary spaceship operated in part by the HAL 9000 (Heuristic ALgorithmic computer) artificial intelligence. " - wikipedia