Audio frequency explained

An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch.[1]

The generally accepted standard hearing range for humans is 20 to 20,000 Hz.[2] [3] [4] In air at atmospheric pressure, these represent sound waves with wavelengths of 17m (56feet) to 1.7cm (00.7inches). Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. Sound frequencies above 20 kHz are called ultrasonic.

Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances.[5] 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.[6] Higher pitches have higher frequency, and lower pitches are lower frequency.

The frequencies an ear can hear are limited to a specific range of frequencies. The audible frequency 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 species have different hearing ranges. For example, some dog breeds can perceive vibrations up to 60,000 Hz.[7]

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.

Frequencies and descriptions

Frequency (Hz)OctaveDescription
16 to 321stThe lower human threshold of hearing, and the lowest pedal notes of a pipe organ.
32 to 5122nd to 5thRhythm frequencies, where the lower and upper bass notes lie.
512 to 2,0486th to 7thDefines human speech intelligibility, gives a horn-like or tinny quality to sound.
2,048 to 8,1928th to 9thGives presence to speech, where labial and fricative sounds lie.
8,192 to 16,38410thBrilliance, the sounds of bells and the ringing of cymbals and sibilance in speech.
16,384 to 32,76811thBeyond brilliance, nebulous sounds approaching and just passing the upper human threshold of hearing
MIDI noteFrequency (Hz)DescriptionSound file
08.17578125Lowest organ noten/a (fundamental frequency inaudible)
1216.3515625Lowest note for tuba, large pipe organs, Bösendorfer Imperial grand pianon/a (fundamental frequency inaudible under average conditions)
2432.703125Lowest C on a standard 88-key piano
3665.40625Lowest note for cello
48130.8125Lowest note for viola, mandola
60261.625Middle C
72523.25C in middle of treble clef
841,046.5Approximately the highest note reproducible by the average female human voice
962,093Highest note for a flute
1084,186Highest note on a standard 88-key piano
1208,372
13216,744Approximately the tone that a typical CRT television emits while running.

See also

Notes and References

  1. Book: Pilhofer . Michael . Music Theory for Dummies. 2007. For Dummies. 97. 9780470167946 .
  2. Web site: Hyperphysics. 19 September 2014.
  3. Heffner. Henry. Heffner. Rickye. Hearing Ranges of Laboratory Animals. Journal of the American Association for Laboratory Animal Science. January 2007. 46. 1. 20–2. 17203911. 19 September 2014.
  4. Book: Rosen, Stuart. Signals and Systems for Speech and Hearing. 2011. BRILL. 163. 2nd. For auditory signals and human listeners, the accepted range is 20Hz to 20kHz, the limits of human hearing.
  5. Web site: Definition of SOUND . 3 October 2016.
  6. Book: Pilhofer . Michael . Music Theory for Dummies . For Dummies . 2007 . 978-0-470-16794-6 . 97.
  7. Web site: Condon . Tim . 2003 . Elert . Glenn . Frequency range of dog hearing . 2008-10-22 . The Physics Factbook.