The crackle of a fireplace, the distant wail of a whale.

If you’ve ever had trouble sleeping, you might have come across sleep sounds as a remedy for insomnia. They’ve also been said to work wonders for deep focus at work or drowning out crying babies for some parental reprieve.

One of the more popular sounds in recent years is white noise, a mix of sounds that creates one powerful constant like a howling vacuum or crashing waves. And then there’s pink noise — the soothing alternative best described as rustling leaves or heartbeats.

Lately, another sonic hue has joined the club — brown noise. TikTokkers have been raving about this magic frequency for improving concentration, relaxation, and sleep.