A new study highlights that certain background noise hurts sleep quality. An experiment by the University of Pennsylvania Perelman School of Medicine shows listening to pink noise led to a nearly 19-minute decrease in REM sleep per night. That is a stage of sleep that has a major impact on memory, mental focus and mood. Pink noise is volume that steadily increases as the pitch gets higher and has a lower pitch than white noise. The study, published in the journal Sleep, also shows airplane noise is linked a 23 minute loss of deep sleep per night.