Phon
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2008-07-10T21:40:01Z
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The '''phon''' was proposed as a [[physical unit|unit]] of [[perception|perceived]] [[loudness]] [[level]] ''L''<sub>N</sub> for pure tones<ref>[http://www.phys.unsw.edu.au/~jw/dB.html#log UNSW Music Acoustics<!-- Bot generated title -->]</ref> by [[S. S. Stevens]]. The purpose of the phon scale is to compensate for the effect of frequency on the perceived loudness of tones.<ref>William M. Hartmann, ''Signals, Sound, and Sensation'', American Institute of Physics, 2004. ISBN 1563962837.</ref> By definition, 1 phon is equal to 1 [[sound pressure level|dBSPL]] at a frequency of 1 [[kHz]].<ref>[http://hyperphysics.phy-astr.gsu.edu/hbase/sound/phon.html Loudness Units: Phons and Sones], HyperPhysics, by C. R. Nave. Accessed [[10 July]] [[2008]].</ref> The [[equal-loudness contour]]s are a way of mapping the dBSPL of a pure tone to the perceived loudness level in phons. These are now defined in the international standard ISO 226:2003, and it should be noted that the research on which this document is based concluded that earlier [[Fletcher–Munson curves]] and [[Robinson-Dadson curves]] were in error.
Although proposed as units, phons are not generally accepted according to the stringent criteria of [[metrology]], and have not been accepted as standard units by the United States [[National Institute of Standards and Technology]].
The phon model can be extended with a time-varying transient model which accounts for "turn-on" (initial transient) and long-term, [[listener fatigue]] effects. This time-varying behavior is the result of [[psychology|psychological]] and [[physiology|physiological]] audio processing. The equal-loudness contours on which the phon is based apply only to the perception of pure steady tones; tests using octave or third-octave bands of noise reveal a different set of curves, owing to the way in which the [[critical band]]s of our hearing integrate power over varying bandwidths and our brain sums the various critical bands.
==See also==
*[[Sone]]
*[[A-weighting]]
==References==
{{reflist}}
*[http://ccrma.stanford.edu/~jos/TimeFreqDisplay/Sones_Phons.html Explanation] with definitions
[[Category:Hearing]]
[[Category:Units of measure]]
[[Category:Human-based units of measure]]
[[Category:Acoustics]]
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