The headband has eeg sensors which monitor brain activity looking for slow-waves (synchronous firing of neurons which define deep sleep).

30 degrees from the peak of a slow-wave we "interrupt" the brain with a brief 50ms pulse of sound. In response to this interruption, your brain increases the synchronous firing of neurons. Resulting in more restorative deep sleep without changing the sleep time.

Is that the sort of description you were looking for?