Pink noise, often compared to the sound of rain or ocean waves, may negatively affect sleep quality, according to a study published on February 3. Researchers from the University of Pennsylvania found that the sound reduced rapid eye movement (REM) sleep, a stage critical for mood regulation and mental focus.
The study, which followed 25 healthy adults over seven nights, found that pink noise reduced REM sleep by an average of 18.6 minutes per night. While the sound helped mask traffic noise, researchers said earplugs were more effective and advised caution when using sound machines, particularly for infants and young children.
Colors are attributed to some types of noise, according to their characteristics. For instance, how a type of noise behaves in a frequency spectrum. An example you might be familiar with is white noise—the kind that can be heard from a radio that's not tuned into a station.
Browse the gallery to learn about the different types of noise and what their colors mean.