Audio frequency

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.<ref>Template:Cite book</ref>

The generally accepted standard hearing range for humans is 20 to 20,000 Hz.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref><ref>Template:Cite book</ref> In air at atmospheric pressure, these represent sound waves with wavelengths of Template:Convert to Template:Convert. 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</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.<ref>Template:Cite book</ref> 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.<ref name="Physics Factbook">{{#invoke:citation/CS1|citation |CitationClass=web }}</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.

Frequencies and descriptionsEdit

Frequency (Hz)	Octave	Description
16 to 32	1st	The lower human threshold of hearing, and the lowest pedal notes of a pipe organ.
32 to 512	2nd to 5th	Rhythm frequencies, where the lower and upper bass notes lie.
512 to 2,048	6th to 7th	Defines human speech intelligibility, gives a horn-like or tinny quality to sound.
2,048 to 8,192	8th to 9th	Gives presence to speech, where labial and fricative sounds lie.
8,192 to 16,384	10th	Brilliance, the sounds of bells and the ringing of cymbals and sibilance in speech.
16,384 to 32,768	11th	Beyond brilliance, nebulous sounds approaching and just passing the upper human threshold of hearing

File:Middle C, or 262 hertz, on a virtual oscilloscope.png

Oscillogram of a pure tone middle C (262 Hz). (Scale: 1 square is equal to 1 millisecond)

File:C5 523 Hz oscillogram.png

C5, an octave above middle C. The frequency is twice that of middle C (523 Hz).

File:C3 131 Hz oscillogram.png

C3, an octave below middle C. The frequency is half that of middle C (131 Hz).

MIDI note	Frequency (Hz)	Description	Sound file
0	8.17578125	Lowest organ note	n/a (fundamental frequency inaudible)
12	16.3515625	Lowest note for tuba, large pipe organs, Bösendorfer Imperial grand piano	n/a (fundamental frequency inaudible under average conditions)
24	32.703125	Lowest C on a standard 88-key piano	File:Audio Frequency tone, C1, 32.70hz.ogg
36	65.40625	Lowest note for cello	File:Audio frequency tone, C2, 65.41hz.ogg
48	130.8125	Lowest note for viola, mandola	File:Audio frequency tone, C3, 130.81hz.ogg
60	261.625	Middle C	File:Audio Frequency tone, Middle C, C4, 261.63hz.ogg
72	523.25	C in middle of treble clef	File:Audio Frequency tone, C5, 523.25hz.ogg
84	1,046.5	Approximately the highest note reproducible by the average female human voice	File:Audio Frequency tone, C6, 1046.50hz.ogg
96	2,093	Highest note for a flute	File:Audio Frequency tone, C7, 2093hz.ogg
108	4,186	Highest note on a standard 88-key piano	File:Audio frequency tone, C8, 4186hz.ogg
120	8,372		File:Audio frequency tone, C9, 8372hz.ogg
132	16,744	Approximately the tone that a typical CRT television emits while running.	File:Audio frequency tone, C10, 16744hz.ogg

ReferencesEdit

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Audio frequency

Frequencies and descriptionsEdit

See alsoEdit

ReferencesEdit