Speak to the Toes
Stanford University researchers have discovered that elephants receive ground signals (low-frequency vocalizations) through their toes. From the news:
"In close quarters, those floppy ears work just fine. To reach elephants miles away, the low-frequency vibrations channel through soil, and clay represents the more reliable long-distance service.
"The 'listening' elephant catches the vibrations with its toes, behind which lie pads of acoustically sensitive fat. Similar tissue is in the heels of the elephant's feet and in its trunk, which augment the toe sensors. The vibrations speed along bones to the elephant's middle ear. They are processed in the auditory cortex area of the brain, just like regular sound."