Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Audio frequency
open-in-new
<p>An audio frequency or audible frequency (AF) is a <a href="/facts/Periodic_function/Sm8lJQsF">periodic</a> <a href="/facts/Vibration/sGgDqG71">vibration</a> whose <a href="/facts/Frequency/QUSbPaW8">frequency</a> is <a href="/facts/Human_hearing_range/QpkSANRw">audible to the average human</a>. The <a href="/facts/SI_unit/S7YLglNz">SI unit</a> of frequency is the <a href="/facts/Hertz/6Wshj5qm">hertz</a> (Hz). It is the property of <a href="/facts/Sound/DlKXlPuF">sound</a> that most determines <a href="/facts/Pitch_(music)/fQAK0JsC">pitch</a>. </p><p>The generally accepted standard <a href="/facts/Hearing_range/QpkSANRw">hearing range</a> for humans is 20 to 20,000 Hz. In air at atmospheric pressure, these represent sound waves with <a href="/facts/Wavelength/kcJU0ymz">wavelengths</a> of 17 metres (56 ft) to 1.7 centimetres (0.67 in). Frequencies below 20 Hz are generally felt rather than heard, assuming the <a href="/facts/Amplitude/aEckuXJM">amplitude</a> of the vibration is great enough. Sound frequencies above 20 kHz are called <a href="/facts/Ultrasonic/31Pa5IH9">ultrasonic</a>. </p><p>Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances. In general, frequency components of a sound determine its "color", its <a href="/facts/Timbre/lVXB949E">timbre</a>. When speaking about the frequency (in singular) of a sound, it means the property that most determines its <a href="/facts/Pitch_(music)/fQAK0JsC">pitch</a>. Higher pitches have higher frequency, and lower pitches are lower frequency. </p><p>The frequencies an ear can hear are limited to a <a href="/facts/Threshold_of_hearing/Fn3TzQ3p">specific range of frequencies</a>. The <a href="/facts/Audible_frequency/LzHtINcf">audible frequency</a> range for humans is typically given as being between about 20 Hz and 20,000 Hz (20 kHz), though the high frequency limit usually reduces with age. Other <a href="/facts/Species/oDg6b96r">species</a> have different hearing ranges. For example, some dog breeds can perceive vibrations up to 60,000 Hz. </p><p>In many media, such as air, the <a href="/facts/Speed_of_sound/dYtbt1nf">speed of sound</a> is approximately independent of frequency, so the wavelength of the sound waves (distance between repetitions) is approximately inversely proportional to frequency. </p>