Andrew Huberman· PhD
There are sound waves, literally particles moving through the air and reverberations that create what we call sound and hearing. And of course there are mechanical stimuli, pressure, light touch, scratch, tickle, et cetera, that lands on our skin or the blowing of a breeze that deflects the hairs on our skin, and we can sense mechanical touch, mechanical sensation. And there are chemicals, there are things floating around in the environment which we call volatile chemicals.