You'll want to read this if you have sleep problems. When sleep doesn’t come easily, many people turn to sound machines, which play steady, non-looping audio — such as pink noise, rainfall or fan sounds — to block out annoying background noises and create a calming environment. But a new study out of the University of Pennsylvania’s Perelman School of Medicine suggests that pink noise-producing machines may actually be disrupting the most restorative stages of sleep for users. The researchers