I use noise-cancelling headphones, which produce a constant, low-volume white-noise, most of the time, for sleep and in public (be careful to visually-confirm personal safety at all times). Not sure if there is any evidence as to harm or benefit, but I would postulate that reducing stimuli over the long-term may atrophy one's ability to filter out noise pollution. (When I was young, most noises would wake me up. In college, living next to a freight train line cured me of that and all noise sensitivities.)