How it works: you can hear a high frequency wave if its modulated at audible frequency. If it's switched on and off at a relatively low frequency, you can sense the presence and absence of the high-frequency vibrations. Those waves are poorly absorbed from the air, but once they make it into the body they are transmitted much more easily by tissues besides bone. So your ears are not much better than the rest of your skin, which acts like a funnel for sound, diverting it to your cochlea.