I got used to the running stream sound, which seems to throw enough transients to mask voices, doors, etc. But I like the retro appeal of an old transistor radio. As a kid, I used to fall asleep listening to hockey games, which had a constant drone of speech almost like a slow-moving auctioneer, punctuated with a bunch of unfamiliar French surnames and the occasional “he scoooores!” If I half-tune it to something like that it could be just the thing.