I use a non-looping white/brown noise machine to help me sleep at night and it works wonders in the city.

One thing I've wondered is the health effects of listening to that noise at ~ 40db all night over all these years. OSHA says that anything under ~ 80db is safe for 8h, but I do wonder if there are any longer term impacts to hearing or audio processing for softer sounds played over a lifetime. I could easily see the brain adapting and 'ignoring' noise in that spectrum. For now, I simply consider the extra sleep I get to be worth the price.