 The whale ear has specific adaptations to the marine environment . In humans , the middle ear works as an impedance equalizer between the outside air 's low impedance and the cochlear fluid 's high impedance . In whales , and other marine mammals , there is no great difference between the outer and inner environments . Instead of sound passing through the outer ear to the middle ear , whales receive sound through the throat , from which it passes through a low @-@ impedance fat @-@ filled cavity to the inner ear . The whale ear is acoustically isolated from the skull by air @-@ filled sinus pockets , which allow for greater directional hearing underwater . Odontocetes send out high frequency clicks from an organ known as a melon . This melon consists of fat , and the skull of any such creature containing a melon will have a large depression . The melon size varies between species , the bigger the more dependent they are of it . A beaked whale for example has a small bulge sitting on top of its skull , whereas a sperm whale 's head is filled up mainly with the melon . 
