The sound of silence? Lull yourself to sleep with soothing white-noise apps

On winter nights, the white-noise app on my phone is tuned to Air Conditioner: a raspy, metallic whir that sounds like the mechanical noise that might echo deep inside the ductwork of a huge commercial building. (Among the app’s other offerings are Dishwasher Rinsing, Crowded Room and Vacuum Cleaner.) It lulls me to sleep nonetheless, because it blankets the din in my apartment (the ragged snore of a roommate; the clanking of the steam radiator; the cat’s skidding pursuit of something only he can see).

It may also soothe because it replicates an early sound environment, probably that of a city childhood, though perhaps it suggests something much, much older. Some sleep experts note that babies, their ears accustomed to the whisper of the maternal circulatory system and the slosh of the womb, sleep better accompanied by a device that mimics those familiar whooshings.

My app is but one note in the mighty chorus of white-noise generators, an exploding industry of mechanical and digital devices; apps and websites, and Sonos and Spotify playlists that grows ever more refined, as if to block out the increased rate of speeding, the wrecks, on the information superhighway.