Andrew Huberman· PhD
In the auditory system, when there's ongoing sound, your auditory system hears that, even if you're not paying attention to it, if you're paying attention to something else, it's still registers. Those little hair cells, as they're called in your inner ear are fluttering, the eardrum is beating and in concert to that sound frequency. And there's a brainstem mechanism that generates alertness and a kind of vigilant.