— PHOTO MOVED IN ADVANCE AND NOT FOR USE – ONLINE OR IN PRINT – BEFORE DEC. 27, 2018. —  In an undated handout photo, the Dohm, a gizmo whose popularity grew by word of mouth and became a favorite not just of light sleepers, but also of psychotherapists, the legal and medical community, and others seeking to mask confidential conversations. White-noise generators are an exploding industry of mechanical and digital devices; apps and websites, and Sonos and Spotify playlists that grows ever more refined. (Handout via The New York Times) — NO SALES; FOR EDITORIAL USE ONLY WITH NYT STORY WHITE NOISE BY PENELOPE GREEN FOR DEC. 27, 2018. ALL OTHER USE PROHIBITED. — XNYT181 XNYT181

How white noise helps you sleep

The first domestic white-noise machine may have been built by a traveling salesman whose wife grew used to the air-conditioners in the motels they frequented...