Editing Cetacea (section)

=== Ears ===
Cetaceans are known to possess excellent hearing.<ref>{{cite web |last1=Mead |first1=James |title=Cetacea |url=https://school.eb.com/levels/high/article/cetacean/105982 |website=Britannica School High |publisher=Encyclopædia Britannica, Inc. |access-date=3 June 2019}}</ref>
[[File:Delfinekko.gif|thumb|upright=1.2|[[Biosonar]] ]]

The external ear has lost the [[Pinna (anatomy)|pinna]] (visible ear), but still retains a narrow [[ear canal]]. The three small bones or [[ossicles]] that transmit sound within each ear are [[Pachyosteosclerosis|dense and compact]], and differently shaped from those of land mammals. The semicircular canals are much smaller relative to body size than in other mammals.<ref name="Thewissen-Hearing">{{cite book | last=[[Hans Thewissen|Thewissen]] | first=J. G. M. | chapter=Hearing | pages=[https://archive.org/details/encyclopediaofma2002unse/page/570 570–572] | title=Encyclopedia of Marine Mammals | editor1-last=Perrin | editor1-first=William R. | editor2-last=Wiirsig | editor2-first=Bernd | editor3-last=[[Hans Thewissen|Thewissen]] | editor3-first=J. G. M. | year=2002 | publisher=Academic Press | isbn=978-0-12-551340-1 | chapter-url=https://archive.org/details/encyclopediaofma2002unse/page/570 }}</ref>

A bony structure of the middle and inner ear, the [[auditory bulla]], is composed of two compact and dense bones (the periotic and tympanic). It is housed in a cavity in the middle ear; in the Odontoceti (apart from in the [[Physeteroidea|physeterids]], this cavity is filled with dense foam{{clarify|what is the foam made of?|date=February 2025}} and completely surrounds the bulla, which is connected to the skull only by ligaments. This may isolate the ear from sounds transmitted through the bones of the skull, something that also happens in [[bat]]s.<ref>{{cite book | last=Ketten | first=Darlene R. | chapter=The Marine Mammal Ear: Specializations for Aquatic Audition and Echolocation | pages=717–750 | title=The Evolutionary Biology of Hearing | editor1-last=Webster | editor1-first=Douglas B. | editor2-last=Fay | editor2-first=Richard R. | editor3-last=Popper | editor3-first=Arthur N. | year=1992 | publisher=Springer | chapter-url=https://www.researchgate.net/publication/230691464}} Pages 725–727 used here.</ref>

Cetaceans use sound to [[communication|communicate]], using groans, moans, whistles, clicks or the 'singing' of the humpback whale.<ref name=":0" />