Editing Audio frequency (section)

{{short description|Sound whose frequency is audible to the average human}}

{{Sound measurements}}

An '''audio frequency''' or '''audible frequency''' ('''AF''') is a [[periodic function|periodic]] [[vibration]] whose [[frequency]] is [[human hearing range|audible to the average human]]. The [[SI unit]] of frequency is the [[hertz]] (Hz). It is the property of [[sound]] that most determines [[Pitch (music)|pitch]].<ref>{{Cite book|last1= Pilhofer |first1=Michael |title=Music Theory for Dummies|url=https://books.google.com/books?id=CxcviUw4KX8C|year=2007|publisher=For Dummies|page=97|isbn=9780470167946 }}</ref>

The generally accepted standard [[hearing range]] for humans is 20 to 20,000&nbsp;Hz.<ref>{{cite web|title=Hyperphysics|url=http://hyperphysics.phy-astr.gsu.edu/hbase/sound/earsens.html|access-date=19 September 2014}}</ref><ref>{{cite journal|last1=Heffner|first1=Henry|last2=Heffner|first2=Rickye|title=Hearing Ranges of Laboratory Animals|journal= Journal of the American Association for Laboratory Animal Science|date=January 2007|volume=46|issue=1|pages=20–2|pmid=17203911|url=http://www.ingentaconnect.com/content/aalas/jaalas/2007/00000046/00000001/art00003|access-date=19 September 2014}}</ref><ref>{{cite book|last=Rosen|first=Stuart|title=Signals and Systems for Speech and Hearing|date=2011|publisher=BRILL|page=163|edition=2nd|quote=For auditory signals and human listeners, the accepted range is 20Hz to 20kHz, the limits of human hearing}}</ref> In air at atmospheric pressure, these represent sound waves with [[wavelength]]s of {{convert|17|m|feet}} to {{convert|1.7|cm|inch}}. Frequencies below 20&nbsp;Hz are generally felt rather than heard, assuming the [[amplitude]] of the vibration is great enough. Sound frequencies above 20&nbsp;kHz are called [[ultrasonic]].

Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances.<ref>{{cite web |title=Definition of SOUND |url=http://www.merriam-webster.com/dictionary/sound |access-date=3 October 2016}}</ref> In general, frequency components of a sound determine its "color", its [[timbre]]. When speaking about the frequency (in singular) of a sound, it means the property that most determines its [[Pitch (music)|pitch]].<ref>{{Cite book |last1=Pilhofer |first1=Michael |url=https://books.google.com/books?id=CxcviUw4KX8C |title=Music Theory for Dummies |publisher=For Dummies |year=2007 |isbn=978-0-470-16794-6 |page=97}}</ref> Higher pitches have higher frequency, and lower pitches are lower frequency. 

The frequencies an ear can hear are limited to a [[Threshold of hearing|specific range of frequencies]].  The [[audible frequency]] range for humans is typically given as being between about 20&nbsp;Hz and 20,000&nbsp;Hz (20&nbsp;kHz), though the high frequency limit usually reduces with age. Other [[species]] have different hearing ranges. For example, some dog breeds can perceive vibrations up to 60,000&nbsp;Hz.<ref name="Physics Factbook">{{cite web |last=Condon |first=Tim |year=2003 |editor-last=Elert |editor-first=Glenn |title=Frequency range of dog hearing |url=https://hypertextbook.com/facts/2003/TimCondon.shtml |accessdate=2008-10-22 |website=The Physics Factbook}}</ref> 

In many media, such as air, the [[speed of sound]] is approximately independent of frequency, so the wavelength of the sound waves (distance between repetitions) is approximately inversely proportional to frequency.