Editing Ultrasound (section)

=== Humans ===
The upper frequency limit in humans (approximately 20&nbsp;kHz) is due to limitations of the [[middle ear]]. [[Ultrasonic hearing|Auditory sensation]] can occur if high‐intensity ultrasound is fed directly into the [[human skull]] and reaches the [[cochlea]] through [[bone conduction]], without passing through the middle ear.<ref>{{cite journal | vauthors = Corso JF |year=1963 |title=Bone-conduction thresholds for sonic and ultrasonic frequencies |journal=Journal of the Acoustical Society of America |volume=35 |issue=11 |pages=1738–1743 |doi=10.1121/1.1918804 |bibcode = 1963ASAJ...35.1738C }}</ref>

Children can hear some high-pitched sounds that older adults cannot hear, because in humans the upper limit pitch of hearing tends to decrease with age.<ref>{{cite journal | vauthors = Takeda S, Morioka I, Miyashita K, Okumura A, Yoshida Y, Matsumoto K | title = Age variation in the upper limit of hearing | journal = European Journal of Applied Physiology and Occupational Physiology | volume = 65 | issue = 5 | pages = 403–8 | year = 1992 | pmid = 1425644 | doi = 10.1007/BF00243505 | s2cid = 33698151 }}</ref> An American [[cell phone]] company has used this to create ring signals that supposedly are only audible to younger humans,<ref>{{cite news | first = Paul | last = Vitello | date = 12 June 2006 | newspaper = The New York Times | url = https://www.nytimes.com/2006/06/12/technology/12ring.html | title = A Ring Tone Meant to Fall on Deaf Ears }}</ref> but many older people can hear the signals, which may be because of the considerable variation of age-related deterioration in the upper hearing threshold.