Sound theory is super mathematical and technical, but in its most basic form, sound is a combination of wavelengths that have different frequencies, or speeds of vibration. “Noise is a selection of individual frequencies playing in a random distribution,” explains Greg McAllister, a senior sound experience manager at Sonos who helps craft the company’s sleep stations for Sonos Radio. “The different flavors of noise are how that frequency distribution is weighted across the range.”

When all of these different frequencies are weighted equally, you get true white noise. Stanford acoustics researcher and neuroscience adviser at Spiritune Daniel Bowling, Ph.D., explains that this equal weighting of frequencies is very unnatural. That is, it sounds more like the static whir of a machine than anything you’d hear if you stepped outside into a forest or beach. (In nature, higher frequencies are not represented as often.)

“White noise is like television static. If you make that really loud, it’s going to be really annoying,” Bowling tells mbg. “The high-frequency content will grab your attention, heighten your arousal, and make you anxious.”

So he notes that while white noise is often discussed as a gold standard for sleep, it’s actually the last thing you’d want to turn on to relax at bedtime.