Editing Frog (section)

===Hearing===
[[File:Synchrotron microtomography of Atelopus franciscus head - pone.0022080.s003.ogv|thumb|Surface rendering of the head of the frog ''[[Atelopus franciscus]]'', with ear parts highlighted]]

Frogs can hear both in the air and below water. They do not have [[Pinna (anatomy)|external ears]]; the eardrums ([[Tympanum (anatomy)|tympanic membranes]]) are directly exposed or may be covered by a layer of skin and are visible as a circular area just behind the eye. The size and distance apart of the eardrums is related to the frequency and wavelength at which the frog calls. In some species such as the bullfrog, the size of the tympanum indicates the sex of the frog; males have tympani that are larger than their eyes while in females, the eyes and tympani are much the same size.<ref name=Neth38>{{cite book |title=Frogs |last=Badger |first=David |author2=Netherton, John |year=1995 |publisher=Airlife Publishing |isbn=978-1-85310-740-5 |page=38 }}</ref> A noise causes the tympanum to vibrate and the sound is transmitted to the middle and inner ear. The middle ear contains semicircular canals which help control balance and orientation. In the inner ear, the auditory hair cells are arranged in two areas of the cochlea, the basilar papilla and the amphibian papilla. The former detects high frequencies and the latter low frequencies.<ref name=Cohen>{{cite book |title=A Natural History of Amphibians |last1=Stebbins |first1=Robert C.|author-link1=Robert C. Stebbins| last2=Cohen|first2= Nathan W. |year=1995 |publisher=Princeton University Press |isbn=978-0-691-03281-8 |pages=67–69 }}</ref> Because the cochlea is short, frogs use [[electrical tuning]] to extend their range of audible frequencies and help discriminate different sounds.<ref>{{cite journal |author1=Armstrong, Cecilia E. |author2=Roberts, William M. |year=1998 |title=Electrical properties of frog saccular hair cells: distortion by enzymatic dissociation |journal=Journal of Neuroscience |volume=18 |issue=8 |pages= 2962–2973 |pmid=9526013 |doi=10.1523/JNEUROSCI.18-08-02962.1998 |pmc=6792591 |doi-access=free }}</ref> This arrangement enables detection of the territorial and breeding calls of their [[Conspecificity|conspecifics]]. In some species that inhabit arid regions, the sound of thunder or heavy rain may arouse them from a dormant state.<ref name=Cohen/> A frog may be startled by an unexpected noise but it will not usually take any action until it has located the source of the sound by sight.<ref name=Neth38/>