For almost sixty years, media technologies have promised users the ability to create sonic safe spaces for themselves--from bedside white noise machines to Beats by Dre's "Hear What You Want" ad campaign, in which Colin Kaepernick's headphones protect him from taunting crowds. In Hush, Mack Hagood draws evidence from noise-canceling headphones, tinnitus maskers, LPs that play ocean sounds, nature-sound mobile apps, and in-ear smart technologies...