phon
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(fŏn) 
n.
A unit of apparent loudness, equal in number to the intensity in decibels of a 1,000-hertz tone perceived to be as loud as the sound being measured.
n.
A unit of apparent loudness, equal in number to the intensity in decibels of a 1,000-hertz tone perceived to be as loud as the sound being measured.
[German, from Greek phōnē, sound. See phone1.]
acoustics. Symbol P. A measure of loudness level, as agreed in 1937 at the first International Acoustical Conference,
[Nature Vol. 140, 370 (1937)] the decibels of sound pressure above 20 μPa of a pure tone of 1 000 Hz subjectively judged by a group of listeners as equally loud as the sound being measured.
[ISO 131:1979 Acoustics - Expression of Physical and Subjective Magnitudes of Sound and Noise in Air] (The reference pressure was 316 μPa earlier.) If p and s represent the loudness respectively in phons and sones, then p = 40 + 10 log2 s.
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For a district in Khon Kaen Province, Thailand, see Phon District.
The phon is a unit of loudness level for pure tones. Its purpose is to compensate for the effect of frequency on the perceived loudness of tones.[1] The phon was proposed in DIN 45631 and ISO 532 B by S. S. Stevens.[2]
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Definition
By definition, 1 phon is equal to 1 dBSPL at a frequency of 1 kHz.[3] The equal-loudness contours are a way of mapping the dBSPL of a pure tone to the perceived loudness level (LN) in phons. These are now defined in the international standard ISO 226:2003, and the research on which this document is based concluded that earlier Fletcher–Munson curves and Robinson-Dadson curves were in error.[citation needed]
The phon unit is not an SI unit in metrology. It has not been accepted as a standard unit by the United States National Institute of Standards and Technology.[citation needed]
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 psychological and 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 bands of our hearing integrate power over varying bandwidths and our brain sums the various critical bands.[clarification needed][citation needed]
See also
References
- ^ William M. Hartmann, Signals, Sound, and Sensation, American Institute of Physics, 2004. ISBN 1-56396-283-7.
- ^ UNSW Music Acoustics
- ^ Nave, C. R. (2002-02-10). Loudness Units: Phons and Sones. HyperPhysics. Retrieved on 2008-07-10 from http://hyperphysics.phy-astr.gsu.edu/hbase/sound/phon.html.
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