72...under appropriate conditions. Sound Receptors.You've got sound receptors in your ear and they are beautiful. We're not going to talk about them at any length, but there's little flappy, these little spiky things going along in your ear and they can translate vibrational energy coming from your ear, hurting your eardrum, being translated into a vibration into the fluid in your ear into a physical motion of these little receptors there into an electrical motion, into an electrical signal that goes into your ear. So, all of that, all of that's pretty impressive stuff. We are not going to talk about the details of it, but I invite some of you who want to learn more about this, particularly MIT students I think find receptors really quite remarkable kinds of devices.