Ultradian rhythm is a rest-activity cycle that regulates cognitive state, mood, and energy level. It consists of roughly 110-minute loops of the energy’s up and down phases. Circadian rhythm is a sleep-wake cycle that regulates the secretion of a sleep hormone called melatonin. It repeats every 24 hours and is constantly fine-tuned through natural light level.
Endel uses these universal rhythms as a baseline for sound personalization. Light has the biggest impact on the circadian rhythm. Even if you aren't exposed to it directly, your body is sensitive to changes in light conditions. article highlights